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Scope of this Document
**********************

This document documents the internals of the GNU debugger, GDB.  It
includes description of GDB's key algorithms and operations, as well as
the mechanisms that adapt GDB to specific hosts and targets.

* Summary::
* Overall Structure::
* Algorithms::
* User Interface::
* libgdb::
* Values::
* Stack Frames::
* Symbol Handling::
* Language Support::
* Host Definition::
* Target Architecture Definition::
* Target Descriptions::
* Target Vector Definition::
* Native Debugging::
* Support Libraries::
* Coding::
* Porting GDB::
* Versions and Branches::
* Start of New Year Procedure::
* Releasing GDB::
* Testsuite::
* Hints::

* GDB Observers::  GDB Currently available observers
* Index::

File: gdbint.info,  Node: Summary,  Next: Overall Structure,  Prev: Top,  Up: Top

1 Summary
*********

* Requirements::
* Contributors::

File: gdbint.info,  Node: Requirements,  Next: Contributors,  Up: Summary

1.1 Requirements
================

Before diving into the internals, you should understand the formal
requirements and other expectations for GDB.  Although some of these
may seem obvious, there have been proposals for GDB that have run
counter to these requirements.

First of all, GDB is a debugger.  It's not designed to be a front
panel for embedded systems.  It's not a text editor.  It's not a shell.
It's not a programming environment.

GDB is an interactive tool.  Although a batch mode is available,
GDB's primary role is to interact with a human programmer.

GDB should be responsive to the user.  A programmer hot on the trail
of a nasty bug, and operating under a looming deadline, is going to be
very impatient of everything, including the response time to debugger
commands.

GDB should be relatively permissive, such as for expressions.  While
the compiler should be picky (or have the option to be made picky),
since source code lives for a long time usually, the programmer doing
debugging shouldn't be spending time figuring out to mollify the
debugger.

GDB will be called upon to deal with really large programs.
Executable sizes of 50 to 100 megabytes occur regularly, and we've
heard reports of programs approaching 1 gigabyte in size.

GDB should be able to run everywhere.  No other debugger is
available for even half as many configurations as GDB supports.

File: gdbint.info,  Node: Contributors,  Prev: Requirements,  Up: Summary

1.2 Contributors
================

The first edition of this document was written by John Gilmore of
Cygnus Solutions. The current second edition was written by Stan Shebs
of Cygnus Solutions, who continues to update the manual.

Over the years, many others have made additions and changes to this
document. This section attempts to record the significant contributors
to that effort. One of the virtues of free software is that everyone is
free to contribute to it; with regret, we cannot actually acknowledge
everyone here.

_Plea:_ This section has only been added relatively recently (four
years after publication of the second edition). Additions to this
section are particularly welcome.  If you or your friends (or
enemies, to be evenhanded) have been unfairly omitted from this

A document such as this relies on being kept up to date by numerous
small updates by contributing engineers as they make changes to the
code base. The file ChangeLog' in the GDB distribution approximates a
blow-by-blow account. The most prolific contributors to this important,
but low profile task are Andrew Cagney (responsible for over half the
entries), Daniel Jacobowitz, Mark Kettenis, Jim Blandy and Eli
Zaretskii.

Eli Zaretskii and Daniel Jacobowitz wrote the sections documenting
watchpoints.

Jeremy Bennett updated the sections on initializing a new
architecture and register representation, and added the section on
Frame Interpretation.

File: gdbint.info,  Node: Overall Structure,  Next: Algorithms,  Prev: Summary,  Up: Top

2 Overall Structure
*******************

GDB consists of three major subsystems: user interface, symbol handling
(the "symbol side"), and target system handling (the "target side").

The user interface consists of several actual interfaces, plus
supporting code.

The symbol side consists of object file readers, debugging info
interpreters, symbol table management, source language expression
parsing, type and value printing.

The target side consists of execution control, stack frame analysis,
and physical target manipulation.

The target side/symbol side division is not formal, and there are a
number of exceptions.  For instance, core file support involves symbolic
elements (the basic core file reader is in BFD) and target elements (it
supplies the contents of memory and the values of registers).  Instead,
this division is useful for understanding how the minor subsystems
should fit together.

2.1 The Symbol Side
===================

The symbolic side of GDB can be thought of as "everything you can do in
GDB without having a live program running".  For instance, you can look
at the types of variables, and evaluate many kinds of expressions.

2.2 The Target Side
===================

The target side of GDB is the "bits and bytes manipulator".  Although
it may make reference to symbolic info here and there, most of the
target side will run with only a stripped executable available--or even
no executable at all, in remote debugging cases.

Operations such as disassembly, stack frame crawls, and register
display, are able to work with no symbolic info at all.  In some cases,
such as disassembly, GDB will use symbolic info to present addresses
relative to symbols rather than as raw numbers, but it will work either
way.

2.3 Configurations
==================

"Host" refers to attributes of the system where GDB runs.  "Target"
refers to the system where the program being debugged executes.  In
most cases they are the same machine, in which case a third type of
"Native" attributes come into play.

Defines and include files needed to build on the host are host
support.  Examples are tty support, system defined types, host byte
order, host float format.  These are all calculated by autoconf' when
the debugger is built.

Defines and information needed to handle the target format are target
dependent.  Examples are the stack frame format, instruction set,
breakpoint instruction, registers, and how to set up and tear down the
stack to call a function.

Information that is only needed when the host and target are the
same, is native dependent.  One example is Unix child process support;
if the host and target are not the same, calling fork' to start the
target process is a bad idea.  The various macros needed for finding the
registers in the upage', running ptrace', and such are all in the
native-dependent files.

Another example of native-dependent code is support for features that
are really part of the target environment, but which require #include'
files that are only available on the host system.  Core file handling
and setjmp' handling are two common cases.

When you want to make GDB work as the traditional native debugger on
a system, you will need to supply both target and native information.

2.4 Source Tree Structure
=========================

The GDB source directory has a mostly flat structure--there are only a
few subdirectories.  A file's name usually gives a hint as to what it
does; for example, stabsread.c' reads stabs, dwarf2read.c' reads
DWARF 2, etc.

Files that are related to some common task have names that share
common substrings.  For example, *-thread.c' files deal with debugging
kinds of symbol and object files; inf*.c' files deal with direct
control of the "inferior program" (GDB parlance for the program being
debugged).

There are several dozens of files in the *-tdep.c' family.  tdep'
stands for "target-dependent code"--each of these files implements
debug support for a specific target architecture (sparc, mips, etc).
Usually, only one of these will be used in a specific GDB configuration
(sometimes two, closely related).

Similarly, there are many *-nat.c' files, each one for native
debugging on a specific system (e.g., sparc-linux-nat.c' is for native
debugging of Sparc machines running the Linux kernel).

The few subdirectories of the source tree are:

cli'
Code that implements "CLI", the GDB Command-Line Interpreter.
*Note Command Interpreter: User Interface.

gdbserver'
Code for the GDB remote server.

gdbtk'
Code for Insight, the GDB TK-based GUI front-end.

mi'
The "GDB/MI", the GDB Machine Interface interpreter.

signals'
Target signal translation code.

tui'
Code for "TUI", the GDB Text-mode full-screen User Interface.
*Note TUI: User Interface.

File: gdbint.info,  Node: Algorithms,  Next: User Interface,  Prev: Overall Structure,  Up: Top

3 Algorithms
************

GDB uses a number of debugging-specific algorithms.  They are often not
very complicated, but get lost in the thicket of special cases and
real-world issues.  This chapter describes the basic algorithms and
mentions some of the specific target definitions that they use.

3.1 Prologue Analysis
=====================

To produce a backtrace and allow the user to manipulate older frames'
variables and arguments, GDB needs to find the base addresses of older
frames, and discover where those frames' registers have been saved.
Since a frame's "callee-saves" registers get saved by younger frames if
and when they're reused, a frame's registers may be scattered
unpredictably across younger frames.  This means that changing the
value of a register-allocated variable in an older frame may actually
entail writing to a save slot in some younger frame.

Modern versions of GCC emit Dwarf call frame information ("CFI"),
which describes how to find frame base addresses and saved registers.
But CFI is not always available, so as a fallback GDB uses a technique
called "prologue analysis" to find frame sizes and saved registers.  A
prologue analyzer disassembles the function's machine code starting
from its entry point, and looks for instructions that allocate frame
space, save the stack pointer in a frame pointer register, save
registers, and so on.  Obviously, this can't be done accurately in
general, but it's tractable to do well enough to be very helpful.
Prologue analysis predates the GNU toolchain's support for CFI; at one
time, prologue analysis was the only mechanism GDB used for stack
unwinding at all, when the function calling conventions didn't specify
a fixed frame layout.

In the olden days, function prologues were generated by hand-written,
target-specific code in GCC, and treated as opaque and untouchable by
optimizers.  Looking at this code, it was usually straightforward to
write a prologue analyzer for GDB that would accurately understand all
the prologues GCC would generate.  However, over time GCC became more
aggressive about instruction scheduling, and began to understand more
about the semantics of the prologue instructions themselves; in
response, GDB's analyzers became more complex and fragile.  Keeping the
prologue analyzers working as GCC (and the instruction sets themselves)

To try to address this problem, the code in prologue-value.h' and
prologue-value.c' provides a general framework for writing prologue
analyzers that are simpler and more robust than ad-hoc analyzers.  When
we analyze a prologue using the prologue-value framework, we're really
doing "abstract interpretation" or "pseudo-evaluation": running the
function's code in simulation, but using conservative approximations of
the values registers and memory would hold when the code actually runs.
For example, if our function starts with the instruction:

we don't know exactly what value will be in r1' after executing
this instruction, but we do know it'll be 42 greater than its original
value.

If we then see an instruction like:

we still don't know what r1's' value is, but again, we can say it
is now 64 greater than its original value.

If the next instruction were:

mov r2, r1      # set r2 to r1's value
then we can say that r2's' value is now the original value of r1'
plus 64.

It's common for prologues to save registers on the stack, so we'll
need to track the values of stack frame slots, as well as the
registers.  So after an instruction like this:

mov (fp+4), r2
then we'd know that the stack slot four bytes above the frame pointer
holds the original value of r1' plus 64.

And so on.

Of course, this can only go so far before it gets unreasonable.  If
we wanted to be able to say anything about the value of r1' after the
instruction:

xor r1, r3      # exclusive-or r1 and r3, place result in r1
then things would get pretty complex.  But remember, we're just doing
a conservative approximation; if exclusive-or instructions aren't
relevant to prologues, we can just say r1''s value is now "unknown".
We can ignore things that are too complex, if that loss of information
is acceptable for our application.

So when we say "conservative approximation" here, what we mean is an
approximation that is either accurate, or marked "unknown", but never
inaccurate.

Using this framework, a prologue analyzer is simply an interpreter
for machine code, but one that uses conservative approximations for the
contents of registers and memory instead of actual values.  Starting
from the function's entry point, you simulate instructions up to the
current PC, or an instruction that you don't know how to simulate.  Now
you can examine the state of the registers and stack slots you've kept
track of.

* To see how large your stack frame is, just check the value of the
stack pointer register; if it's the original value of the SP minus
a constant, then that constant is the stack frame's size.  If the
SP's value has been marked as "unknown", then that means the
prologue has done something too complex for us to track, and we
don't know the frame size.

* To see where we've saved the previous frame's registers, we just
search the values we've tracked -- stack slots, usually, but
registers, too, if you want -- for something equal to the
register's original value.  If the calling conventions suggest a
standard place to save a given register, then we can check there
first, but really, anything that will get us back the original
value will probably work.

This does take some work.  But prologue analyzers aren't
quick-and-simple pattern patching to recognize a few fixed prologue
forms any more; they're big, hairy functions.  Along with inferior
function calls, prologue analysis accounts for a substantial portion of
the time needed to stabilize a GDB port.  So it's worthwhile to look
for an approach that will be easier to understand and maintain.  In the
approach described above:

* It's easier to see that the analyzer is correct: you just see
whether the analyzer properly (albeit conservatively) simulates
the effect of each instruction.

* It's easier to extend the analyzer: you can add support for new
instructions, and know that you haven't broken anything that

* It's orthogonal: to gather new information, you don't need to
complicate the code for each instruction.  As long as your domain
of conservative values is already detailed enough to tell you what
you need, then all the existing instruction simulations are
already gathering the right data for you.

The file prologue-value.h' contains detailed comments explaining
the framework and how to use it.

3.2 Breakpoint Handling
=======================

In general, a breakpoint is a user-designated location in the program
where the user wants to regain control if program execution ever reaches
that location.

There are two main ways to implement breakpoints; either as
"hardware" breakpoints or as "software" breakpoints.

Hardware breakpoints are sometimes available as a builtin debugging
features with some chips.  Typically these work by having dedicated
register into which the breakpoint address may be stored.  If the PC
(shorthand for "program counter") ever matches a value in a breakpoint
registers, the CPU raises an exception and reports it to GDB.

Another possibility is when an emulator is in use; many emulators
include circuitry that watches the address lines coming out from the
processor, and force it to stop if the address matches a breakpoint's

A third possibility is that the target already has the ability to do
breakpoints somehow; for instance, a ROM monitor may do its own
software breakpoints.  So although these are not literally "hardware
breakpoints", from GDB's point of view they work the same; GDB need not
do anything more than set the breakpoint and wait for something to
happen.

Since they depend on hardware resources, hardware breakpoints may be
limited in number; when the user asks for more, GDB will start trying
to set software breakpoints.  (On some architectures, notably the
32-bit x86 platforms, GDB cannot always know whether there's enough
hardware resources to insert all the hardware breakpoints and
watchpoints.  On those platforms, GDB prints an error message only when
the program being debugged is continued.)

Software breakpoints require GDB to do somewhat more work.  The
basic theory is that GDB will replace a program instruction with a
trap, illegal divide, or some other instruction that will cause an
exception, and then when it's encountered, GDB will take the exception
and stop the program.  When the user says to continue, GDB will restore
the original instruction, single-step, re-insert the trap, and continue
on.

Since it literally overwrites the program being tested, the program
area must be writable, so this technique won't work on programs in ROM.
It can also distort the behavior of programs that examine themselves,
although such a situation would be highly unusual.

Also, the software breakpoint instruction should be the smallest
size of instruction, so it doesn't overwrite an instruction that might
be a jump target, and cause disaster when the program jumps into the
middle of the breakpoint instruction.  (Strictly speaking, the
breakpoint must be no larger than the smallest interval between
instructions that may be jump targets; perhaps there is an architecture
where only even-numbered instructions may jumped to.)  Note that it's
possible for an instruction set not to have any instructions usable for
a software breakpoint, although in practice only the ARC has failed to
define such an instruction.

Basic breakpoint object handling is in breakpoint.c'.  However,
much of the interesting breakpoint action is in infrun.c'.

target_remove_breakpoint (BP_TGT)'
target_insert_breakpoint (BP_TGT)'
Insert or remove a software breakpoint at address
BP_TGT->placed_address'.  Returns zero for success, non-zero for
failure.  On input, BP_TGT contains the address of the breakpoint,
and is otherwise initialized to zero.  The fields of the struct
bp_target_info' pointed to by BP_TGT are updated to contain other
information about the breakpoint on output.  The field
placed_address' may be updated if the breakpoint was placed at a
related address; the field shadow_contents' contains the real
contents of the bytes where the breakpoint has been inserted, if
underlying memory; the field shadow_len' is the length of memory
cached in shadow_contents', if any; and the field placed_size'
is optionally set and used by the target, if it could differ from
shadow_len'.

For example, the remote target Z0' packet does not require
shadowing memory, so shadow_len' is left at zero.  However, the
length reported by gdbarch_breakpoint_from_pc' is cached in
placed_size', so that a matching z0' packet can be used to
remove the breakpoint.

target_remove_hw_breakpoint (BP_TGT)'
target_insert_hw_breakpoint (BP_TGT)'
Insert or remove a hardware-assisted breakpoint at address
BP_TGT->placed_address'.  Returns zero for success, non-zero for
failure.  See target_insert_breakpoint' for a description of the
struct bp_target_info' pointed to by BP_TGT; the
shadow_contents' and shadow_len' members are not used for
hardware breakpoints, but placed_size' may be.

3.3 Single Stepping
===================

3.4 Signal Handling
===================

===================

3.6 Inferior Function Calls
===========================

3.7 Longjmp Support
===================

GDB has support for figuring out that the target is doing a longjmp'
and for stopping at the target of the jump, if we are stepping.  This
is done with a few specialized internal breakpoints, which are visible
in the output of the maint info breakpoint' command.

To make this work, you need to define a function called
gdbarch_get_longjmp_target', which will examine the jmp_buf'
structure and extract the longjmp' target address.  Since jmp_buf' is
target specific and typically defined in a target header not available
to GDB, you will need to determine the offset of the PC manually and
return that; many targets define a jb_pc_offset' field in the tdep
structure to save the value once calculated.

3.8 Watchpoints
===============

Watchpoints are a special kind of breakpoints (*note breakpoints:
Algorithms.) which break when data is accessed rather than when some
instruction is executed.  When you have data which changes without your
knowing what code does that, watchpoints are the silver bullet to hunt
down and kill such bugs.

Watchpoints can be either hardware-assisted or not; the latter type
is known as "software watchpoints."  GDB always uses hardware-assisted
watchpoints if they are available, and falls back on software
watchpoints otherwise.  Typical situations where GDB will use software
watchpoints are:

* The watched memory region is too large for the underlying hardware
watchpoint support.  For example, each x86 debug register can
watch up to 4 bytes of memory, so trying to watch data structures
whose size is more than 16 bytes will cause GDB to use software
watchpoints.

* The value of the expression to be watched depends on data held in
registers (as opposed to memory).

* Too many different watchpoints requested.  (On some architectures,
this situation is impossible to detect until the debugged program
is resumed.)  Note that x86 debug registers are used both for
hardware breakpoints and for watchpoints, so setting too many
hardware breakpoints might cause watchpoint insertion to fail.

* No hardware-assisted watchpoints provided by the target
implementation.

Software watchpoints are very slow, since GDB needs to single-step
the program being debugged and test the value of the watched
expression(s) after each instruction.  The rest of this section is
mostly irrelevant for software watchpoints.

When the inferior stops, GDB tries to establish, among other
possible reasons, whether it stopped due to a watchpoint being hit.  It
first uses STOPPED_BY_WATCHPOINT' to see if any watchpoint was hit.
If not, all watchpoint checking is skipped.

Then GDB calls target_stopped_data_address' exactly once.  This
method returns the address of the watchpoint which triggered, if the
target can determine it.  If the triggered address is available, GDB
compares the address returned by this method with each watched memory
watchpoints, GDB announces every watchpoint that watches the triggered
watchpoints _require_ that the triggered address be available; if not,
read and access watchpoints will never be considered hit.  For
data-write watchpoints, if the triggered address is available, GDB
considers only those watchpoints which match that address; otherwise,
GDB considers all data-write watchpoints.  For each data-write
watchpoint that GDB considers, it evaluates the expression whose value
is being watched, and tests whether the watched value has changed.
Watchpoints whose watched values have changed are announced as hit.

GDB uses several macros and primitives to support hardware
watchpoints:

TARGET_CAN_USE_HARDWARE_WATCHPOINT (TYPE, COUNT, OTHER)'
Return the number of hardware watchpoints of type TYPE that are
possible to be set.  The value is positive if COUNT watchpoints of
this type can be set, zero if setting watchpoints of this type is
not supported, and negative if COUNT is more than the maximum
number of watchpoints of type TYPE that can be set.  OTHER is
non-zero if other types of watchpoints are currently enabled (there
are architectures which cannot set watchpoints of different types
at the same time).

TARGET_REGION_OK_FOR_HW_WATCHPOINT (ADDR, LEN)'
Return non-zero if hardware watchpoints can be used to watch a
region whose address is ADDR and whose length in bytes is LEN.

target_remove_watchpoint (ADDR, LEN, TYPE)'
Insert or remove a hardware watchpoint starting at ADDR, for LEN
bytes.  TYPE is the watchpoint type, one of the possible values of
the enumerated data type target_hw_bp_type', defined by
breakpoint.h' as follows:

enum target_hw_bp_type
{
hw_write   = 0, /* Common (write) HW watchpoint */
hw_access  = 2, /* Access (read or write) HW watchpoint */
hw_execute = 3  /* Execute HW breakpoint */
};

These two macros should return 0 for success, non-zero for failure.

If the inferior has some watchpoint that triggered, place the
address associated with the watchpoint at the location pointed to
by ADDR_P and return non-zero.  Otherwise, return zero.  This is
required for data-read and data-access watchpoints.  It is not
required for data-write watchpoints, but GDB uses it to improve
handling of those also.

GDB will only call this method once per watchpoint stop,
immediately after calling STOPPED_BY_WATCHPOINT'.  If the
target's watchpoint indication is sticky, i.e., stays set after
resuming, this method should clear it.  For instance, the x86 debug
control register has sticky triggered flags.

Check whether ADDR (as returned by target_stopped_data_address')
lies within the hardware-defined watchpoint region described by
START and LENGTH.  This only needs to be provided if the
granularity of a watchpoint is greater than one byte, i.e., if the
watchpoint can also trigger on nearby addresses outside of the
watched region.

HAVE_STEPPABLE_WATCHPOINT'
If defined to a non-zero value, it is not necessary to disable a
watchpoint to step over it.  Like
gdbarch_have_nonsteppable_watchpoint', this is usually set when
watchpoints trigger at the instruction which will perform an
interesting read or write.  It should be set if there is a
temporary disable bit which allows the processor to step over the
interesting instruction without raising the watchpoint exception
again.

int gdbarch_have_nonsteppable_watchpoint (GDBARCH)'
If it returns a non-zero value, GDB should disable a watchpoint to
step the inferior over it.  This is usually set when watchpoints
trigger at the instruction which will perform an interesting read
or write.

HAVE_CONTINUABLE_WATCHPOINT'
If defined to a non-zero value, it is possible to continue the
inferior after a watchpoint has been hit.  This is usually set
when watchpoints trigger at the instruction following an

STOPPED_BY_WATCHPOINT (WAIT_STATUS)'
Return non-zero if stopped by a watchpoint.  WAIT_STATUS is of the
type struct target_waitstatus', defined by target.h'.  Normally,
this macro is defined to invoke the function pointed to by the
to_stopped_by_watchpoint' member of the structure (of the type
target_ops', defined on target.h') that describes the
target-specific operations; to_stopped_by_watchpoint' ignores the
WAIT_STATUS argument.

GDB does not require the non-zero value returned by
STOPPED_BY_WATCHPOINT' to be 100% correct, so if a target cannot
determine for sure whether the inferior stopped due to a
watchpoint, it could return non-zero "just in case".

-----------------------------

GDB only supports process-wide watchpoints, which trigger in all
threads.  GDB uses the thread ID to make watchpoints act as if they
were thread-specific, but it cannot set hardware watchpoints that only
trigger in a specific thread.  Therefore, even if the target supports
a single thread, it should set the per-thread debug registers for all
threads to the same value.  On GNU/Linux native targets, this is
accomplished by using ALL_LWPS' in target_insert_watchpoint' and
target_remove_watchpoint' and by using linux_set_new_thread' to
register a handler for newly created threads.

GDB's GNU/Linux support only reports a single event at a time,
although multiple events can trigger simultaneously for multi-threaded
programs.  When multiple events occur, linux-nat.c' queues subsequent
events and returns them the next time the program is resumed.  This
means that STOPPED_BY_WATCHPOINT' and target_stopped_data_address'
by inferior_ptid'.  If two threads have hit watchpoints
simultaneously, those routines will be called a second time for the

3.8.2 x86 Watchpoints
---------------------

The 32-bit Intel x86 (a.k.a. ia32) processors feature special debug
registers designed to facilitate debugging.  GDB provides a generic
library of functions that x86-based ports can use to implement support
for watchpoints and hardware-assisted breakpoints.  This subsection
documents the x86 watchpoint facilities in GDB.

(At present, the library functions read and write debug registers
directly, and are thus only available for native configurations.)

To use the generic x86 watchpoint support, a port should do the
following:

* Define the macro I386_USE_GENERIC_WATCHPOINTS' somewhere in the

* Include the config/i386/nm-i386.h' header file _after_ defining
I386_USE_GENERIC_WATCHPOINTS'.

* Add i386-nat.o' to the value of the Make variable NATDEPFILES'
(*note NATDEPFILES: Native Debugging.).

* Provide implementations for the I386_DR_LOW_*' macros described
below.  Typically, each macro should call a target-specific
function which does the real work.

The x86 watchpoint support works by maintaining mirror images of the
debug registers.  Values are copied between the mirror images and the
real debug registers via a set of macros which each target needs to
provide:

I386_DR_LOW_SET_CONTROL (VAL)'
Set the Debug Control (DR7) register to the value VAL.

I386_DR_LOW_SET_ADDR (IDX, ADDR)'

Reset (i.e. zero out) the address stored in the debug register
number IDX.

I386_DR_LOW_GET_STATUS'
Return the value of the Debug Status (DR6) register.  This value is
used immediately after it is returned by I386_DR_LOW_GET_STATUS',
so as to support per-thread status register values.

For each one of the 4 debug registers (whose indices are from 0 to 3)
that store addresses, a reference count is maintained by GDB, to allow
sharing of debug registers by several watchpoints.  This allows users
to define several watchpoints that watch the same expression, but with
different conditions and/or commands, without wasting debug registers
which are in short supply.  GDB maintains the reference counts
internally, targets don't have to do anything to use this feature.

The x86 debug registers can each watch a region that is 1, 2, or 4
bytes long.  The ia32 architecture requires that each watched region be
appropriately aligned: 2-byte region on 2-byte boundary, 4-byte region
on 4-byte boundary.  However, the x86 watchpoint support in GDB can
watch unaligned regions and regions larger than 4 bytes (up to 16
bytes) by allocating several debug registers to watch a single region.
This allocation of several registers per a watched region is also done
automatically without target code intervention.

The generic x86 watchpoint support provides the following API for the
GDB's application code:

i386_region_ok_for_watchpoint (ADDR, LEN)'
The macro TARGET_REGION_OK_FOR_HW_WATCHPOINT' is set to call this
function.  It counts the number of debug registers required to
watch a given region, and returns a non-zero value if that number
is less than 4, the number of debug registers available to x86
processors.

i386_stopped_data_address (ADDR_P)'
The target function target_stopped_data_address' is set to call
this function.  This function examines the breakpoint condition
bits in the DR6 Debug Status register, as returned by the
I386_DR_LOW_GET_STATUS' macro, and returns the address associated
with the first bit that is set in DR6.

i386_stopped_by_watchpoint (void)'
The macro STOPPED_BY_WATCHPOINT' is set to call this function.
The argument passed to STOPPED_BY_WATCHPOINT' is ignored.  This
function examines the breakpoint condition bits in the DR6 Debug
Status register, as returned by the I386_DR_LOW_GET_STATUS'
macro, and returns true if any bit is set.  Otherwise, false is
returned.

i386_remove_watchpoint (ADDR, LEN, TYPE)'
Insert or remove a watchpoint.  The macros
target_insert_watchpoint' and target_remove_watchpoint' are set
to call these functions.  i386_insert_watchpoint' first looks for
a debug register which is already set to watch the same region for
the same access types; if found, it just increments the reference
count of that debug register, thus implementing debug register
sharing between watchpoints.  If no such register is found, the
function looks for a vacant debug register, sets its mirrored
value to ADDR, sets the mirrored value of DR7 Debug Control
register as appropriate for the LEN and TYPE parameters, and then
passes the new values of the debug register and DR7 to the
inferior by calling I386_DR_LOW_SET_ADDR' and
I386_DR_LOW_SET_CONTROL'.  If more than one debug register is
required to cover the given region, the above process is repeated
for each debug register.

i386_remove_watchpoint' does the opposite: it resets the address
in the mirrored value of the debug register and its read/write and
length bits in the mirrored value of DR7, then passes these new
values to the inferior via I386_DR_LOW_RESET_ADDR' and
I386_DR_LOW_SET_CONTROL'.  If a register is shared by several
watchpoints, each time a i386_remove_watchpoint' is called, it
decrements the reference count, and only calls
I386_DR_LOW_RESET_ADDR' and I386_DR_LOW_SET_CONTROL' when the
count goes to zero.

i386_insert_hw_breakpoint (BP_TGT)'
i386_remove_hw_breakpoint (BP_TGT)'
These functions insert and remove hardware-assisted breakpoints.
The macros target_insert_hw_breakpoint' and
target_remove_hw_breakpoint' are set to call these functions.
The argument is a struct bp_target_info *', as described in the
documentation for target_insert_breakpoint'.  These functions
work like i386_insert_watchpoint' and i386_remove_watchpoint',
respectively, except that they set up the debug registers to watch
instruction execution, and each hardware-assisted breakpoint
always requires exactly one debug register.

i386_cleanup_dregs (void)'
This function clears all the reference counts, addresses, and
control bits in the mirror images of the debug registers.  It
doesn't affect the actual debug registers in the inferior process.

*Notes:*
1. x86 processors support setting watchpoints on I/O reads or writes.
However, since no target supports this (as of March 2001), and
since enum target_hw_bp_type' doesn't even have an enumeration
for I/O watchpoints, this feature is not yet available to GDB
running on x86.

2. x86 processors can enable watchpoints locally, for the current task
only, or globally, for all the tasks.  For each debug register,
there's a bit in the DR7 Debug Control register that determines
whether the associated address is watched locally or globally.  The
current implementation of x86 watchpoint support in GDB always
sets watchpoints to be locally enabled, since global watchpoints
might interfere with the underlying OS and are probably
unavailable in many platforms.

3.9 Checkpoints
===============

In the abstract, a checkpoint is a point in the execution history of
the program, which the user may wish to return to at some later time.

Internally, a checkpoint is a saved copy of the program state,
including whatever information is required in order to restore the
program to that state at a later time.  This can be expected to include
the state of registers and memory, and may include external state such
as the state of open files and devices.

There are a number of ways in which checkpoints may be implemented
in gdb, e.g. as corefiles, as forked processes, and as some opaque
method implemented on the target side.

A corefile can be used to save an image of target memory and register
state, which can in principle be restored later -- but corefiles do not
typically include information about external entities such as open
files.  Currently this method is not implemented in gdb.

A forked process can save the state of user memory and registers, as
well as some subset of external (kernel) state.  This method is used to
implement checkpoints on Linux, and in principle might be used on other
systems.

Some targets, e.g. simulators, might have their own built-in method
for saving checkpoints, and gdb might be able to take advantage of that
capability without necessarily knowing any details of how it is done.

3.10 Observing changes in GDB internals
=======================================

In order to function properly, several modules need to be notified when
some changes occur in the GDB internals.  Traditionally, these modules
have relied on several paradigms, the most common ones being hooks and
gdb-events.  Unfortunately, none of these paradigms was versatile
enough to become the standard notification mechanism in GDB.  The fact
that they only supported one "client" was also a strong limitation.

A new paradigm, based on the Observer pattern of the Design
Patterns' book, has therefore been implemented.  The goal was to provide
a new interface overcoming the issues with the notification mechanisms
previously available.  This new interface needed to be strongly typed,
easy to extend, and versatile enough to be used as the standard

See *note GDB Observers:: for a brief description of the observers
currently implemented in GDB. The rationale for the current
implementation is also briefly discussed.

File: gdbint.info,  Node: User Interface,  Next: libgdb,  Prev: Algorithms,  Up: Top

4 User Interface
****************

GDB has several user interfaces, of which the traditional command-line
interface is perhaps the most familiar.

4.1 Command Interpreter
=======================

The command interpreter in GDB is fairly simple.  It is designed to
allow for the set of commands to be augmented dynamically, and also has
a recursive subcommand capability, where the first argument to a
command may itself direct a lookup on a different command list.

For instance, the set' command just starts a lookup on the
setlist' command list, while set thread' recurses to the
set_thread_cmd_list'.

To add commands in general, use add_cmd'.  add_com' adds to the
main command list, and should be used for those commands.  The usual
place to add commands is in the _initialize_XYZ' routines at the ends
of most source files.

To add paired set' and show' commands, use add_setshow_cmd' or
add_setshow_cmd_full'.  The former is a slightly simpler interface
which is useful when you don't need to further modify the new command
structures, while the latter returns the new command structures for
manipulation.

Before removing commands from the command set it is a good idea to
deprecate them for some time.  Use deprecate_cmd' on commands or
aliases to set the deprecated flag.  deprecate_cmd' takes a struct
cmd_list_element' as it's first argument.  You can use the return value
from add_com' or add_cmd' to deprecate the command immediately after
it is created.

The first time a command is used the user will be warned and offered
a replacement (if one exists). Note that the replacement string passed
to deprecate_cmd' should be the full name of the command, i.e., the
entire string the user should type at the command line.

4.2 UI-Independent Output--the ui_out' Functions
=================================================

The ui_out' functions present an abstraction level for the GDB output
code.  They hide the specifics of different user interfaces supported
by GDB, and thus free the programmer from the need to write several
versions of the same code, one each for every UI, to produce output.

4.2.1 Overview and Terminology
------------------------------

In general, execution of each GDB command produces some sort of output,
and can even generate an input request.

Output can be generated for the following purposes:

* to display a _result_ of an operation;

* to convey _info_ or produce side-effects of a requested operation;

* to provide a _notification_ of an asynchronous event (including
progress indication of a prolonged asynchronous operation);

* to display _error messages_ (including warnings);

* to show _debug data_;

* to _query_ or prompt a user for input (a special case).

This section mainly concentrates on how to build result output,
although some of it also applies to other kinds of output.

Generation of output that displays the results of an operation
involves one or more of the following:

* output of the actual data

* formatting the output as appropriate for console output, to make it

* machine oriented formatting-a more terse formatting to allow for
easy parsing by programs which read GDB's output

* annotation, whose purpose is to help legacy GUIs to identify
interesting parts in the output

The ui_out' routines take care of the first three aspects.
Annotations are provided by separate annotation routines.  Note that use
of annotations for an interface between a GUI and GDB is deprecated.

Output can be in the form of a single item, which we call a "field";
a "list" consisting of identical fields; a "tuple" consisting of
non-identical fields; or a "table", which is a tuple consisting of a
header and a body.  In a BNF-like form:

<table> ==>'
<header> <body>'

{ <column> }'

<column> ==>'
<width> <alignment> <title>'

<body> ==>'
{<row>}'

4.2.2 General Conventions
-------------------------

Most ui_out' routines are of type void', the exceptions are
ui_out_stream_new' (which returns a pointer to the newly created
object) and the make_cleanup' routines.

The first parameter is always the ui_out' vector object, a pointer
to a struct ui_out'.

The FORMAT parameter is like in printf' family of functions.  When
it is present, there must also be a variable list of arguments
sufficient used to satisfy the %' specifiers in the supplied format.

When a character string argument is not used in a ui_out' function
call, a NULL' pointer has to be supplied instead.

4.2.3 Table, Tuple and List Functions
-------------------------------------

This section introduces ui_out' routines for building lists, tuples
and tables.  The routines to output the actual data items (fields) are
presented in the next section.

To recap: A "tuple" is a sequence of "fields", each field containing
information about an object; a "list" is a sequence of fields where
each field describes an identical object.

Use the "table" functions when your output consists of a list of
rows (tuples) and the console output should include a heading.  Use this
even when you are listing just one object but you still want the header.

Tables can not be nested.  Tuples and lists can be nested up to a
maximum of five levels.

The overall structure of the table output code is something like
this:

ui_out_table_begin
...
ui_out_table_body
ui_out_tuple_begin
ui_out_field_*
...
ui_out_tuple_end
...
ui_out_table_end

Here is the description of table-, tuple- and list-related ui_out'
functions:

-- Function: void ui_out_table_begin (struct ui_out *UIOUT, int
NBROFCOLS, int NR_ROWS, const char *TBLID)
The function ui_out_table_begin' marks the beginning of the output
of a table.  It should always be called before any other ui_out'
function for a given table.  NBROFCOLS is the number of columns in
the table. NR_ROWS is the number of rows in the table.  TBLID is
an optional string identifying the table.  The string pointed to
by TBLID is copied by the implementation of ui_out_table_begin',
so the application can free the string if it was malloc'ed.

The companion function ui_out_table_end', described below, marks
the end of the table's output.

-- Function: void ui_out_table_header (struct ui_out *UIOUT, int
WIDTH, enum ui_align ALIGNMENT, const char *COLHDR)
ui_out_table_header' provides the header information for a single
table column.  You call this function several times, one each for
every column of the table, after ui_out_table_begin', but before
ui_out_table_body'.

The value of WIDTH gives the column width in characters.  The
value of ALIGNMENT is one of left', center', and right', and it
specifies how to align the header: left-justify, center, or
right-justify it.  COLHDR points to a string that specifies the
column header; the implementation copies that string, so column
header strings in malloc'ed storage can be freed after the call.

-- Function: void ui_out_table_body (struct ui_out *UIOUT)
This function delimits the table header from the table body.

-- Function: void ui_out_table_end (struct ui_out *UIOUT)
This function signals the end of a table's output.  It should be
called after the table body has been produced by the list and
field output functions.

There should be exactly one call to ui_out_table_end' for each
call to ui_out_table_begin', otherwise the ui_out' functions
will signal an internal error.

The output of the tuples that represent the table rows must follow
the call to ui_out_table_body' and precede the call to
ui_out_table_end'.  You build a tuple by calling ui_out_tuple_begin'
and ui_out_tuple_end', with suitable calls to functions which actually
output fields between them.

-- Function: void ui_out_tuple_begin (struct ui_out *UIOUT, const char
*ID)
This function marks the beginning of a tuple output.  ID points to
an optional string that identifies the tuple; it is copied by the
implementation, and so strings in malloc'ed storage can be freed
after the call.

-- Function: void ui_out_tuple_end (struct ui_out *UIOUT)
This function signals an end of a tuple output.  There should be
exactly one call to ui_out_tuple_end' for each call to
ui_out_tuple_begin', otherwise an internal GDB error will be
signaled.

-- Function: struct cleanup * make_cleanup_ui_out_tuple_begin_end
(struct ui_out *UIOUT, const char *ID)
This function first opens the tuple and then establishes a cleanup
(*note Cleanups: Coding.) to close the tuple.  It provides a
convenient and correct implementation of the non-portable(1) code
sequence:
struct cleanup *old_cleanup;
ui_out_tuple_begin (uiout, "...");
old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
uiout);

-- Function: void ui_out_list_begin (struct ui_out *UIOUT, const char
*ID)
This function marks the beginning of a list output.  ID points to
an optional string that identifies the list; it is copied by the
implementation, and so strings in malloc'ed storage can be freed
after the call.

-- Function: void ui_out_list_end (struct ui_out *UIOUT)
This function signals an end of a list output.  There should be
exactly one call to ui_out_list_end' for each call to
ui_out_list_begin', otherwise an internal GDB error will be
signaled.

-- Function: struct cleanup * make_cleanup_ui_out_list_begin_end
(struct ui_out *UIOUT, const char *ID)
Similar to make_cleanup_ui_out_tuple_begin_end', this function
opens a list and then establishes cleanup (*note Cleanups: Coding.)
that will close the list.

4.2.4 Item Output Functions
---------------------------

The functions described below produce output for the actual data items,
or fields, which contain information about the object.

Choose the appropriate function accordingly to your particular needs.

-- Function: void ui_out_field_fmt (struct ui_out *UIOUT, char
*FLDNAME, char *FORMAT, ...)
This is the most general output function.  It produces the
representation of the data in the variable-length argument list
according to formatting specifications in FORMAT, a printf'-like
format string.  The optional argument FLDNAME supplies the name of
the field.  The data items themselves are supplied as additional
arguments after FORMAT.

This generic function should be used only when it is not possible
to use one of the specialized versions (see below).

-- Function: void ui_out_field_int (struct ui_out *UIOUT, const char
*FLDNAME, int VALUE)
This function outputs a value of an int' variable.  It uses the
"%d"' output conversion specification.  FLDNAME specifies the
name of the field.

-- Function: void ui_out_field_fmt_int (struct ui_out *UIOUT, int
WIDTH, enum ui_align ALIGNMENT, const char *FLDNAME, int
VALUE)
This function outputs a value of an int' variable.  It differs
from ui_out_field_int' in that the caller specifies the desired
WIDTH and ALIGNMENT of the output.  FLDNAME specifies the name of
the field.

-- Function: void ui_out_field_core_addr (struct ui_out *UIOUT, const
This function outputs an address as appropriate for GDBARCH.

-- Function: void ui_out_field_string (struct ui_out *UIOUT, const
char *FLDNAME, const char *STRING)
This function outputs a string using the "%s"' conversion
specification.

Sometimes, there's a need to compose your output piece by piece using
functions that operate on a stream, such as value_print' or
fprintf_symbol_filtered'.  These functions accept an argument of the
type struct ui_file *', a pointer to a ui_file' object used to store
the data stream used for the output.  When you use one of these
functions, you need a way to pass their results stored in a ui_file'
object to the ui_out' functions.  To this end, you first create a
ui_stream' object by calling ui_out_stream_new', pass the stream'
member of that ui_stream' object to value_print' and similar
functions, and finally call ui_out_field_stream' to output the field
you constructed.  When the ui_stream' object is no longer needed, you
should destroy it and free its memory by calling ui_out_stream_delete'.

-- Function: struct ui_stream * ui_out_stream_new (struct ui_out
*UIOUT)
This function creates a new ui_stream' object which uses the same
output methods as the ui_out' object whose pointer is passed in
UIOUT.  It returns a pointer to the newly created ui_stream'
object.

-- Function: void ui_out_stream_delete (struct ui_stream *STREAMBUF)
This functions destroys a ui_stream' object specified by
STREAMBUF.

-- Function: void ui_out_field_stream (struct ui_out *UIOUT, const
char *FIELDNAME, struct ui_stream *STREAMBUF)
This function consumes all the data accumulated in
streambuf->stream' and outputs it like ui_out_field_string'
does.  After a call to ui_out_field_stream', the accumulated data
no longer exists, but the stream is still valid and may be used
for producing more fields.

*Important:* If there is any chance that your code could bail out
before completing output generation and reaching the point where
ui_out_stream_delete' is called, it is necessary to set up a cleanup,
to avoid leaking memory and other resources.  Here's a skeleton code to
do that:

struct ui_stream *mybuf = ui_out_stream_new (uiout);
struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
...
do_cleanups (old);

If the function already has the old cleanup chain set (for other
kinds of cleanups), you just have to add your cleanup to it:

mybuf = ui_out_stream_new (uiout);
make_cleanup (ui_out_stream_delete, mybuf);

Note that with cleanups in place, you should not call
ui_out_stream_delete' directly, or you would attempt to free the same
buffer twice.

4.2.5 Utility Output Functions
------------------------------

-- Function: void ui_out_field_skip (struct ui_out *UIOUT, const char
*FLDNAME)
This function skips a field in a table.  Use it if you have to
leave an empty field without disrupting the table alignment.  The
argument FLDNAME specifies a name for the (missing) filed.

-- Function: void ui_out_text (struct ui_out *UIOUT, const char
*STRING)
This function outputs the text in STRING in a way that makes it
easy to be read by humans.  For example, the console
implementation of this method filters the text through a built-in
pager, to prevent it from scrolling off the visible portion of the
screen.

Use this function for printing relatively long chunks of text
around the actual field data: the text it produces is not aligned
according to the table's format.  Use ui_out_field_string' to
output a string field, and use ui_out_message', described below,
to output short messages.

-- Function: void ui_out_spaces (struct ui_out *UIOUT, int NSPACES)
This function outputs NSPACES spaces.  It is handy to align the
text produced by ui_out_text' with the rest of the table or list.

-- Function: void ui_out_message (struct ui_out *UIOUT, int VERBOSITY,
const char *FORMAT, ...)
This function produces a formatted message, provided that the
current verbosity level is at least as large as given by
VERBOSITY.  The current verbosity level is specified by the user
with the set verbositylevel' command.(2)

-- Function: void ui_out_wrap_hint (struct ui_out *UIOUT, char *INDENT)
This function gives the console output filter (a paging filter) a
hint of where to break lines which are too long.  Ignored for all
other output consumers.  INDENT, if non-NULL', is the string to
be printed to indent the wrapped text on the next line; it must
remain accessible until the next call to ui_out_wrap_hint', or
until an explicit newline is produced by one of the other
functions.  If INDENT is NULL', the wrapped text will not be
indented.

-- Function: void ui_out_flush (struct ui_out *UIOUT)
This function flushes whatever output has been accumulated so far,
if the UI buffers output.

4.2.6 Examples of Use of ui_out' functions
-------------------------------------------

This section gives some practical examples of using the ui_out'
functions to generalize the old console-oriented code in GDB.  The
examples all come from functions defined on the breakpoints.c' file.

This example, from the breakpoint_1' function, shows how to produce
a table.

The original code was:

if (!found_a_breakpoint++)
{

annotate_field (0);
printf_filtered ("Num ");
annotate_field (1);
printf_filtered ("Type           ");
annotate_field (2);
printf_filtered ("Disp ");
annotate_field (3);
printf_filtered ("Enb ");
{
annotate_field (4);
}
annotate_field (5);
printf_filtered ("What\n");

annotate_breakpoints_table ();
}

Here's the new version:

nr_printable_breakpoints = ...;

ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
else
ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");

if (nr_printable_breakpoints > 0)
if (nr_printable_breakpoints > 0)
annotate_field (0);
ui_out_table_header (uiout, 3, ui_left, "number", "Num");		/* 1 */
if (nr_printable_breakpoints > 0)
annotate_field (1);
ui_out_table_header (uiout, 14, ui_left, "type", "Type");		/* 2 */
if (nr_printable_breakpoints > 0)
annotate_field (2);
ui_out_table_header (uiout, 4, ui_left, "disp", "Disp");		/* 3 */
if (nr_printable_breakpoints > 0)
annotate_field (3);
ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb");	/* 4 */
{
if (nr_printable_breakpoints > 0)
annotate_field (4);
else
}
if (nr_printable_breakpoints > 0)
annotate_field (5);
ui_out_table_header (uiout, 40, ui_noalign, "what", "What");	/* 6 */
ui_out_table_body (uiout);
if (nr_printable_breakpoints > 0)
annotate_breakpoints_table ();

This example, from the print_one_breakpoint' function, shows how to
produce the actual data for the table whose structure was defined in
the above example.  The original code was:

annotate_record ();
annotate_field (0);
printf_filtered ("%-3d ", b->number);
annotate_field (1);
if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
|| ((int) b->type != bptypes[(int) b->type].type))
internal_error ("bptypes table does not describe type #%d.",
(int)b->type);
printf_filtered ("%-14s ", bptypes[(int)b->type].description);
annotate_field (2);
printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
annotate_field (3);
printf_filtered ("%-3c ", bpenables[(int)b->enable]);
...

This is the new version:

annotate_record ();
ui_out_tuple_begin (uiout, "bkpt");
annotate_field (0);
ui_out_field_int (uiout, "number", b->number);
annotate_field (1);
if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
|| ((int) b->type != bptypes[(int) b->type].type))
internal_error ("bptypes table does not describe type #%d.",
(int) b->type);
ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
annotate_field (2);
ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
annotate_field (3);
ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
...

This example, also from print_one_breakpoint', shows how to produce
a complicated output field using the print_expression' functions which
requires a stream to be passed.  It also shows how to automate stream
destruction with cleanups.  The original code was:

annotate_field (5);
print_expression (b->exp, gdb_stdout);

The new version is:

struct ui_stream *stb = ui_out_stream_new (uiout);
struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
...
annotate_field (5);
print_expression (b->exp, stb->stream);
ui_out_field_stream (uiout, "what", local_stream);

This example, also from print_one_breakpoint', shows how to use
ui_out_text' and ui_out_field_string'.  The original code was:

annotate_field (5);
if (b->dll_pathname == NULL)
printf_filtered ("<any library> ");
else
printf_filtered ("library \"%s\" ", b->dll_pathname);

It became:

annotate_field (5);
if (b->dll_pathname == NULL)
{
ui_out_field_string (uiout, "what", "<any library>");
ui_out_spaces (uiout, 1);
}
else
{
ui_out_text (uiout, "library \"");
ui_out_field_string (uiout, "what", b->dll_pathname);
ui_out_text (uiout, "\" ");
}

The following example from print_one_breakpoint' shows how to use
ui_out_field_int' and ui_out_spaces'.  The original code was:

annotate_field (5);
if (b->forked_inferior_pid != 0)
printf_filtered ("process %d ", b->forked_inferior_pid);

It became:

annotate_field (5);
if (b->forked_inferior_pid != 0)
{
ui_out_text (uiout, "process ");
ui_out_field_int (uiout, "what", b->forked_inferior_pid);
ui_out_spaces (uiout, 1);
}

Here's an example of using ui_out_field_string'.  The original code
was:

annotate_field (5);
if (b->exec_pathname != NULL)
printf_filtered ("program \"%s\" ", b->exec_pathname);

It became:

annotate_field (5);
if (b->exec_pathname != NULL)
{
ui_out_text (uiout, "program \"");
ui_out_field_string (uiout, "what", b->exec_pathname);
ui_out_text (uiout, "\" ");
}

Finally, here's an example of printing an address.  The original
code:

annotate_field (4);
printf_filtered ("%s ",

It became:

annotate_field (4);

4.3 Console Printing
====================

4.4 TUI
=======

---------- Footnotes ----------

(1) The function cast is not portable ISO C.

(2) As of this writing (April 2001), setting verbosity level is not
yet implemented, and is always returned as zero.  So calling
ui_out_message' with a VERBOSITY argument more than zero will cause
the message to never be printed.

File: gdbint.info,  Node: libgdb,  Next: Values,  Prev: User Interface,  Up: Top

5 libgdb
********

5.1 libgdb 1.0
==============

libgdb' 1.0 was an abortive project of years ago.  The theory was to
provide an API to GDB's functionality.

5.2 libgdb 2.0
==============

libgdb' 2.0 is an ongoing effort to update GDB so that is better able
to support graphical and other environments.

Since libgdb' development is on-going, its architecture is still
evolving.  The following components have so far been identified:

* Observer - gdb-events.h'.

* Builder - ui-out.h'

* Event Loop - event-loop.h'

* Library - gdb.h'

The model that ties these components together is described below.

5.3 The libgdb' Model
======================

A client of libgdb' interacts with the library in two ways.

* As an observer (using gdb-events') receiving notifications from
libgdb' of any internal state changes (break point changes, run
state, etc).

* As a client querying libgdb' (using the ui-out' builder) to
obtain various status values from GDB.

Since libgdb' could have multiple clients (e.g., a GUI supporting
the existing GDB CLI), those clients must co-operate when controlling
libgdb'.  In particular, a client must ensure that libgdb' is idle
(i.e. no other client is using libgdb') before responding to a
gdb-event' by making a query.

5.4 CLI support
===============

At present GDB's CLI is very much entangled in with the core of
libgdb'.  Consequently, a client wishing to include the CLI in their
interface needs to carefully co-ordinate its own and the CLI's
requirements.

It is suggested that the client set libgdb' up to be bi-modal
(alternate between CLI and client query modes).  The notes below sketch
out the theory:

* The client registers itself as an observer of libgdb'.

* The client create and install cli-out' builder using its own
versions of the ui-file' gdb_stderr', gdb_stdtarg' and
gdb_stdout' streams.

* The client creates a separate custom ui-out' builder that is only
used while making direct queries to libgdb'.

When the client receives input intended for the CLI, it simply
passes it along.  Since the cli-out' builder is installed by default,
all the CLI output in response to that command is routed (pronounced
rooted) through to the client controlled gdb_stdout' et. al. streams.
At the same time, the client is kept abreast of internal changes by
virtue of being a libgdb' observer.

The only restriction on the client is that it must wait until
libgdb' becomes idle before initiating any queries (using the client's
custom builder).

5.5 libgdb' components
=======================

Observer - gdb-events.h'
-------------------------

gdb-events' provides the client with a very raw mechanism that can be
used to implement an observer.  At present it only allows for one
observer and that observer must, internally, handle the need to delay
the processing of any event notifications until after libgdb' has
finished the current command.

Builder - ui-out.h'
--------------------

ui-out' provides the infrastructure necessary for a client to create a
builder.  That builder is then passed down to libgdb' when doing any
queries.

Event Loop - event-loop.h'
---------------------------

event-loop', currently non-re-entrant, provides a simple event loop.
A client would need to either plug its self into this loop or,
implement a new event-loop that GDB would use.

The event-loop will eventually be made re-entrant.  This is so that
GDB can better handle the problem of some commands blocking instead of
returning.

Library - gdb.h'
-----------------

libgdb' is the most obvious component of this system.  It provides the
query interface.  Each function is parameterized by a ui-out' builder.
The result of the query is constructed using that builder before the
query function returns.

File: gdbint.info,  Node: Values,  Next: Stack Frames,  Prev: libgdb,  Up: Top

6 Values
********

6.1 Values
==========

GDB uses struct value', or "values", as an internal abstraction for
the representation of a variety of inferior objects and GDB convenience
objects.

Values have an associated struct type', that describes a virtual
view of the raw data or object stored in or accessed through the value.

A value is in addition discriminated by its lvalue-ness, given its
enum lval_type' enumeration type:

not_lval''
This value is not an lval.  It can't be assigned to.

lval_memory''
This value represents an object in memory.

lval_register''
This value represents an object that lives in a register.

lval_internalvar''
Represents the value of an internal variable.

lval_internalvar_component''
Represents part of a GDB internal variable.  E.g., a structure
field.

lval_computed''
These are "computed" values.  They allow creating specialized value
objects for specific purposes, all abstracted away from the core
value support code.  The creator of such a value writes specialized
functions to handle the reading and writing to/from the value's
backend data, and optionally, a "copy operator" and a "destructor".

Pointers to these functions are stored in a struct lval_funcs'
instance (declared in value.h'), and passed to the
allocate_computed_value' function, as in the example below.

static void
{
/* This callback reads data from some backend, and stores it in V.
In this case, we always read null data.  You'll want to fill in
something more interesting.  */

memset (value_contents_all_raw (v),
value_offset (v),
TYPE_LENGTH (value_type (v)));
}

static void
nil_value_write (struct value *v, struct value *fromval)
{
/* Takes the data from FROMVAL and stores it in the backend of V.  */

to_oblivion (value_contents_all_raw (fromval),
value_offset (v),
TYPE_LENGTH (value_type (fromval)));
}

static struct lval_funcs nil_value_funcs =
{
nil_value_write
};

struct value *
make_nil_value (void)
{
struct type *type;
struct value *v;

type = make_nils_type ();
v = allocate_computed_value (type, &nil_value_funcs, NULL);

return v;
}

See the implementation of the _siginfo' convenience variable in infrun.c' as a real example use of lval_computed. File: gdbint.info, Node: Stack Frames, Next: Symbol Handling, Prev: Values, Up: Top 7 Stack Frames ************** A frame is a construct that GDB uses to keep track of calling and called functions. GDB's frame model, a fresh design, was implemented with the need to support DWARF's Call Frame Information in mind. In fact, the term "unwind" is taken directly from that specification. Developers wishing to learn more about unwinders, are encouraged to read the DWARF specification, available from http://www.dwarfstd.org'. GDB's model is that you find a frame's registers by "unwinding" them from the next younger frame. That is, get_frame_register' which returns the value of a register in frame #1 (the next-to-youngest frame), is implemented by calling frame #0's frame_register_unwind' (the youngest frame). But then the obvious question is: how do you access the registers of the youngest frame itself? To answer this question, GDB has the "sentinel" frame, the "-1st" frame. Unwinding registers from the sentinel frame gives you the current values of the youngest real frame's registers. If F is a sentinel frame, then get_frame_type (F) == SENTINEL_FRAME'. 7.1 Selecting an Unwinder ========================= The architecture registers a list of frame unwinders (struct frame_unwind'), using the functions frame_unwind_prepend_unwinder' and frame_unwind_append_unwinder'. Each unwinder includes a sniffer. Whenever GDB needs to unwind a frame (to fetch the previous frame's registers or the current frame's ID), it calls registered sniffers in order to find one which recognizes the frame. The first time a sniffer returns non-zero, the corresponding unwinder is assigned to the frame. 7.2 Unwinding the Frame ID ========================== Every frame has an associated ID, of type struct frame_id'. The ID includes the stack base and function start address for the frame. The ID persists through the entire life of the frame, including while other called frames are running; it is used to locate an appropriate struct frame_info' from the cache. Every time the inferior stops, and at various other times, the frame cache is flushed. Because of this, parts of GDB which need to keep track of individual frames cannot use pointers to struct frame_info'. A frame ID provides a stable reference to a frame, even when the unwinder must be run again to generate a new struct frame_info' for the same frame. The frame's unwinder's this_id' method is called to find the ID. Note that this is different from register unwinding, where the next frame's prev_register' is called to unwind this frame's registers. Both stack base and function address are required to identify the frame, because a recursive function has the same function address for two consecutive frames and a leaf function may have the same stack address as its caller. On some platforms, a third address is part of the ID to further disambiguate frames--for instance, on IA-64 the separate register stack address is included in the ID. An invalid frame ID (outer_frame_id') returned from the this_id' method means to stop unwinding after this frame. null_frame_id' is another invalid frame ID which should be used when there is no frame. For instance, certain breakpoints are attached to a specific frame, and that frame is identified through its frame ID (we use this to implement the "finish" command). Using null_frame_id' as the frame ID for a given breakpoint means that the breakpoint is not specific to any frame. The this_id' method should never return null_frame_id'. 7.3 Unwinding Registers ======================= Each unwinder includes a prev_register' method. This method takes a frame, an associated cache pointer, and a register number. It returns a struct value *' describing the requested register, as saved by this frame. This is the value of the register that is current in this frame's caller. The returned value must have the same type as the register. It may have any lvalue type. In most circumstances one of these routines will generate the appropriate value: frame_unwind_got_optimized' This register was not saved. frame_unwind_got_register' This register was copied into another register in this frame. This is also used for unchanged registers; they are "copied" into the same register. frame_unwind_got_memory' This register was saved in memory. frame_unwind_got_constant' This register was not saved, but the unwinder can compute the previous value some other way. frame_unwind_got_address' Same as frame_unwind_got_constant', except that the value is a target address. This is frequently used for the stack pointer, which is not explicitly saved but has a known offset from this frame's stack pointer. For architectures with a flat unified address space, this is generally the same as frame_unwind_got_constant'. File: gdbint.info, Node: Symbol Handling, Next: Language Support, Prev: Stack Frames, Up: Top 8 Symbol Handling ***************** Symbols are a key part of GDB's operation. Symbols include variables, functions, and types. Symbol information for a large program can be truly massive, and reading of symbol information is one of the major performance bottlenecks in GDB; it can take many minutes to process it all. Studies have shown that nearly all the time spent is computational, rather than file reading. One of the ways for GDB to provide a good user experience is to start up quickly, taking no more than a few seconds. It is simply not possible to process all of a program's debugging info in that time, and so we attempt to handle symbols incrementally. For instance, we create "partial symbol tables" consisting of only selected symbols, and only expand them to full symbol tables when necessary. * Menu: * Symbol Reading:: * Partial Symbol Tables:: * Types:: * Object File Formats:: * Debugging File Formats:: * Adding a New Symbol Reader to GDB:: * Memory Management for Symbol Files:: * Memory Management for Types:: File: gdbint.info, Node: Symbol Reading, Next: Partial Symbol Tables, Up: Symbol Handling 8.1 Symbol Reading ================== GDB reads symbols from "symbol files". The usual symbol file is the file containing the program which GDB is debugging. GDB can be directed to use a different file for symbols (with the symbol-file' command), and it can also read more symbols via the add-file' and load' commands. In addition, it may bring in more symbols while loading shared libraries. Symbol files are initially opened by code in symfile.c' using the BFD library (*note Support Libraries::). BFD identifies the type of the file by examining its header. find_sym_fns' then uses this identification to locate a set of symbol-reading functions. Symbol-reading modules identify themselves to GDB by calling add_symtab_fns' during their module initialization. The argument to add_symtab_fns' is a struct sym_fns' which contains the name (or name prefix) of the symbol format, the length of the prefix, and pointers to four functions. These functions are called at various times to process symbol files whose identification matches the specified prefix. The functions supplied by each module are: XYZ_symfile_init(struct sym_fns *sf)' Called from symbol_file_add' when we are about to read a new symbol file. This function should clean up any internal state (possibly resulting from half-read previous files, for example) and prepare to read a new symbol file. Note that the symbol file which we are reading might be a new "main" symbol file, or might be a secondary symbol file whose symbols are being added to the existing symbol table. The argument to XYZ_symfile_init' is a newly allocated struct sym_fns' whose bfd' field contains the BFD for the new symbol file being read. Its private' field has been zeroed, and can be modified as desired. Typically, a struct of private information will be malloc''d, and a pointer to it will be placed in the private' field. There is no result from XYZ_symfile_init', but it can call error' if it detects an unavoidable problem. XYZ_new_init()' Called from symbol_file_add' when discarding existing symbols. This function needs only handle the symbol-reading module's internal state; the symbol table data structures visible to the rest of GDB will be discarded by symbol_file_add'. It has no arguments and no result. It may be called after XYZ_symfile_init', if a new symbol table is being read, or may be called alone if all symbols are simply being discarded. XYZ_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)' Called from symbol_file_add' to actually read the symbols from a symbol-file into a set of psymtabs or symtabs. sf' points to the struct sym_fns' originally passed to XYZ_sym_init' for possible initialization. addr' is the offset between the file's specified start address and its true address in memory. mainline' is 1 if this is the main symbol table being read, and 0 if a secondary symbol file (e.g., shared library or dynamically loaded file) is being read. In addition, if a symbol-reading module creates psymtabs when XYZ_symfile_read is called, these psymtabs will contain a pointer to a function XYZ_psymtab_to_symtab', which can be called from any point in the GDB symbol-handling code. XYZ_psymtab_to_symtab (struct partial_symtab *pst)' Called from psymtab_to_symtab' (or the PSYMTAB_TO_SYMTAB' macro) if the psymtab has not already been read in and had its pst->symtab' pointer set. The argument is the psymtab to be fleshed-out into a symtab. Upon return, pst->readin' should have been set to 1, and pst->symtab' should contain a pointer to the new corresponding symtab, or zero if there were no symbols in that part of the symbol file. File: gdbint.info, Node: Partial Symbol Tables, Next: Types, Prev: Symbol Reading, Up: Symbol Handling 8.2 Partial Symbol Tables ========================= GDB has three types of symbol tables: * Full symbol tables ("symtabs"). These contain the main information about symbols and addresses. * Partial symbol tables ("psymtabs"). These contain enough information to know when to read the corresponding part of the full symbol table. * Minimal symbol tables ("msymtabs"). These contain information gleaned from non-debugging symbols. This section describes partial symbol tables. A psymtab is constructed by doing a very quick pass over an executable file's debugging information. Small amounts of information are extracted--enough to identify which parts of the symbol table will need to be re-read and fully digested later, when the user needs the information. The speed of this pass causes GDB to start up very quickly. Later, as the detailed rereading occurs, it occurs in small pieces, at various times, and the delay therefrom is mostly invisible to the user. The symbols that show up in a file's psymtab should be, roughly, those visible to the debugger's user when the program is not running code from that file. These include external symbols and types, static symbols and types, and enum' values declared at file scope. The psymtab also contains the range of instruction addresses that the full symbol table would represent. The idea is that there are only two ways for the user (or much of the code in the debugger) to reference a symbol: * By its address (e.g., execution stops at some address which is inside a function in this file). The address will be noticed to be in the range of this psymtab, and the full symtab will be read in. find_pc_function', find_pc_line', and other find_pc_...' functions handle this. * By its name (e.g., the user asks to print a variable, or set a breakpoint on a function). Global names and file-scope names will be found in the psymtab, which will cause the symtab to be pulled in. Local names will have to be qualified by a global name, or a file-scope name, in which case we will have already read in the symtab as we evaluated the qualifier. Or, a local symbol can be referenced when we are "in" a local scope, in which case the first case applies. lookup_symbol' does most of the work here. The only reason that psymtabs exist is to cause a symtab to be read in at the right moment. Any symbol that can be elided from a psymtab, while still causing that to happen, should not appear in it. Since psymtabs don't have the idea of scope, you can't put local symbols in them anyway. Psymtabs don't have the idea of the type of a symbol, either, so types need not appear, unless they will be referenced by name. It is a bug for GDB to behave one way when only a psymtab has been read, and another way if the corresponding symtab has been read in. Such bugs are typically caused by a psymtab that does not contain all the visible symbols, or which has the wrong instruction address ranges. The psymtab for a particular section of a symbol file (objfile) could be thrown away after the symtab has been read in. The symtab should always be searched before the psymtab, so the psymtab will never be used (in a bug-free environment). Currently, psymtabs are allocated on an obstack, and all the psymbols themselves are allocated in a pair of large arrays on an obstack, so there is little to be gained by trying to free them unless you want to do a lot more work. Whether or not psymtabs are created depends on the objfile's symbol reader. The core of GDB hides the details of partial symbols and partial symbol tables behind a set of function pointers known as the "quick symbol functions". These are documented in symfile.h'. File: gdbint.info, Node: Types, Next: Object File Formats, Prev: Partial Symbol Tables, Up: Symbol Handling 8.3 Types ========= Fundamental Types (e.g., FT_VOID', FT_BOOLEAN'). -------------------------------------------------- These are the fundamental types that GDB uses internally. Fundamental types from the various debugging formats (stabs, ELF, etc) are mapped into one of these. They are basically a union of all fundamental types that GDB knows about for all the languages that GDB knows about. Type Codes (e.g., TYPE_CODE_PTR', TYPE_CODE_ARRAY'). ------------------------------------------------------ Each time GDB builds an internal type, it marks it with one of these types. The type may be a fundamental type, such as TYPE_CODE_INT', or a derived type, such as TYPE_CODE_PTR' which is a pointer to another type. Typically, several FT_*' types map to one TYPE_CODE_*' type, and are distinguished by other members of the type struct, such as whether the type is signed or unsigned, and how many bits it uses. Builtin Types (e.g., builtin_type_void', builtin_type_char'). --------------------------------------------------------------- These are instances of type structs that roughly correspond to fundamental types and are created as global types for GDB to use for various ugly historical reasons. We eventually want to eliminate these. Note for example that builtin_type_int' initialized in gdbtypes.c' is basically the same as a TYPE_CODE_INT' type that is initialized in c-lang.c' for an FT_INTEGER' fundamental type. The difference is that the builtin_type' is not associated with any particular objfile, and only one instance exists, while c-lang.c' builds as many TYPE_CODE_INT' types as needed, with each one associated with some particular objfile. File: gdbint.info, Node: Object File Formats, Next: Debugging File Formats, Prev: Types, Up: Symbol Handling 8.4 Object File Formats ======================= 8.4.1 a.out ----------- The a.out' format is the original file format for Unix. It consists of three sections: text', data', and bss', which are for program code, initialized data, and uninitialized data, respectively. The a.out' format is so simple that it doesn't have any reserved place for debugging information. (Hey, the original Unix hackers used adb', which is a machine-language debugger!) The only debugging format for a.out' is stabs, which is encoded as a set of normal symbols with distinctive attributes. The basic a.out' reader is in dbxread.c'. 8.4.2 COFF ---------- The COFF format was introduced with System V Release 3 (SVR3) Unix. COFF files may have multiple sections, each prefixed by a header. The number of sections is limited. The COFF specification includes support for debugging. Although this was a step forward, the debugging information was woefully limited. For instance, it was not possible to represent code that came from an included file. GNU's COFF-using configs often use stabs-type info, encapsulated in special sections. The COFF reader is in coffread.c'. 8.4.3 ECOFF ----------- ECOFF is an extended COFF originally introduced for Mips and Alpha workstations. The basic ECOFF reader is in mipsread.c'. 8.4.4 XCOFF ----------- The IBM RS/6000 running AIX uses an object file format called XCOFF. The COFF sections, symbols, and line numbers are used, but debugging symbols are dbx'-style stabs whose strings are located in the .debug' section (rather than the string table). For more information, see *note Top: (stabs)Top. The shared library scheme has a clean interface for figuring out what shared libraries are in use, but the catch is that everything which refers to addresses (symbol tables and breakpoints at least) needs to be relocated for both shared libraries and the main executable. At least using the standard mechanism this can only be done once the program has been run (or the core file has been read). 8.4.5 PE -------- Windows 95 and NT use the PE ("Portable Executable") format for their executables. PE is basically COFF with additional headers. While BFD includes special PE support, GDB needs only the basic COFF reader. 8.4.6 ELF --------- The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar to COFF in being organized into a number of sections, but it removes many of COFF's limitations. Debugging info may be either stabs encapsulated in ELF sections, or more commonly these days, DWARF. The basic ELF reader is in elfread.c'. 8.4.7 SOM --------- SOM is HP's object file and debug format (not to be confused with IBM's SOM, which is a cross-language ABI). The SOM reader is in somread.c'. File: gdbint.info, Node: Debugging File Formats, Next: Adding a New Symbol Reader to GDB, Prev: Object File Formats, Up: Symbol Handling 8.5 Debugging File Formats ========================== This section describes characteristics of debugging information that are independent of the object file format. 8.5.1 stabs ----------- stabs' started out as special symbols within the a.out' format. Since then, it has been encapsulated into other file formats, such as COFF and ELF. While dbxread.c' does some of the basic stab processing, including for encapsulated versions, stabsread.c' does the real work. 8.5.2 COFF ---------- The basic COFF definition includes debugging information. The level of support is minimal and non-extensible, and is not often used. 8.5.3 Mips debug (Third Eye) ---------------------------- ECOFF includes a definition of a special debug format. The file mdebugread.c' implements reading for this format. 8.5.4 DWARF 2 ------------- DWARF 2 is an improved but incompatible version of DWARF 1. The DWARF 2 reader is in dwarf2read.c'. 8.5.5 Compressed DWARF 2 ------------------------ Compressed DWARF 2 is not technically a separate debugging format, but merely DWARF 2 debug information that has been compressed. In this format, every object-file section holding DWARF 2 debugging information is compressed and prepended with a header. (The section is also typically renamed, so a section called .debug_info' in a DWARF 2 binary would be called .zdebug_info' in a compressed DWARF 2 binary.) The header is 12 bytes long: * 4 bytes: the literal string "ZLIB" * 8 bytes: the uncompressed size of the section, in big-endian byte order. The same reader is used for both compressed an normal DWARF 2 info. Section decompression is done in zlib_decompress_section' in dwarf2read.c'. 8.5.6 DWARF 3 ------------- DWARF 3 is an improved version of DWARF 2. 8.5.7 SOM --------- Like COFF, the SOM definition includes debugging information. File: gdbint.info, Node: Adding a New Symbol Reader to GDB, Next: Memory Management for Symbol Files, Prev: Debugging File Formats, Up: Symbol Handling 8.6 Adding a New Symbol Reader to GDB ===================================== If you are using an existing object file format (a.out', COFF, ELF, etc), there is probably little to be done. If you need to add a new object file format, you must first add it to BFD. This is beyond the scope of this document. You must then arrange for the BFD code to provide access to the debugging symbols. Generally GDB will have to call swapping routines from BFD and a few other BFD internal routines to locate the debugging information. As much as possible, GDB should not depend on the BFD internal data structures. For some targets (e.g., COFF), there is a special transfer vector used to call swapping routines, since the external data structures on various platforms have different sizes and layouts. Specialized routines that will only ever be implemented by one object file format may be called directly. This interface should be described in a file bfd/libXYZ.h', which is included by GDB. File: gdbint.info, Node: Memory Management for Symbol Files, Next: Memory Management for Types, Prev: Adding a New Symbol Reader to GDB, Up: Symbol Handling 8.7 Memory Management for Symbol Files ====================================== Most memory associated with a loaded symbol file is stored on its objfile_obstack'. This includes symbols, types, namespace data, and other information produced by the symbol readers. Because this data lives on the objfile's obstack, it is automatically released when the objfile is unloaded or reloaded. Therefore one objfile must not reference symbol or type data from another objfile; they could be unloaded at different times. File: gdbint.info, Node: Memory Management for Types, Prev: Memory Management for Symbol Files, Up: Symbol Handling 8.8 Memory Management for Types =============================== TYPE_OBJFILE' macro indicates the current memory owner of the type. Non-NULL' value indicates it is owned by an objfile (specifically by its obstack) and in such case the type remains valid till the objfile is unloaded or reloaded. For such types with an associated objfile no reference counting is being made. User convenience variables, et cetera, have associated types. Normally these types live in the associated objfile. However, when the objfile is unloaded, those types are deep copied to global memory, so that the values of the user variables and history items are not lost. During the copy they will get their TYPE_OBJFILE' set to NULL' and become so-called "reclaimable" types. Types with null TYPE_OBJFILE' can be either permanent types (*note Builtin Types::) or reclaimable types which will be deallocated at the first idle GDB moment if the last object referencing them is removed. Permanent types are allocated by the function alloc_type' (and its derivations like init_type') specifying objfile as NULL'. The reclaimable types are created the same way but moreover they need to have type_init_group' called to start their tracking as being possibly deallocatable. When GDB gets idle it always calls the free_all_types' function which deallocates any unused types. All types currently not owned by an objfile must be marked as used on each free_all_types' call as they would get deallocated as unused otherwise. free_all_types' automatically checks for any cross-type references such as through TYPE_TARGET_TYPE', TYPE_POINTER_TYPE' etc. and prevents early deallocation for any such existing references. Reclaimable types may reference any other reclaimable types or even permanent types. But permanent types must not reference reclaimable types (nor an objfile associated type). File: gdbint.info, Node: Language Support, Next: Host Definition, Prev: Symbol Handling, Up: Top 9 Language Support ****************** GDB's language support is mainly driven by the symbol reader, although it is possible for the user to set the source language manually. GDB chooses the source language by looking at the extension of the file recorded in the debug info; .c' means C, .f' means Fortran, etc. It may also use a special-purpose language identifier if the debug format supports it, like with DWARF. 9.1 Adding a Source Language to GDB =================================== To add other languages to GDB's expression parser, follow the following steps: _Create the expression parser._ This should reside in a file LANG-exp.y'. Routines for building parsed expressions into a union exp_element' list are in parse.c'. Since we can't depend upon everyone having Bison, and YACC produces parsers that define a bunch of global names, the following lines *must* be included at the top of the YACC parser, to prevent the various parsers from defining the same global names: #define yyparse LANG_parse #define yylex LANG_lex #define yyerror LANG_error #define yylval LANG_lval #define yychar LANG_char #define yydebug LANG_debug #define yypact LANG_pact #define yyr1 LANG_r1 #define yyr2 LANG_r2 #define yydef LANG_def #define yychk LANG_chk #define yypgo LANG_pgo #define yyact LANG_act #define yyexca LANG_exca #define yyerrflag LANG_errflag #define yynerrs LANG_nerrs At the bottom of your parser, define a struct language_defn' and initialize it with the right values for your language. Define an initialize_LANG' routine and have it call add_language(LANG_language_defn)' to tell the rest of GDB that your language exists. You'll need some other supporting variables and functions, which will be used via pointers from your LANG_language_defn'. See the declaration of struct language_defn' in language.h', and the other *-exp.y' files, for more information. _Add any evaluation routines, if necessary_ If you need new opcodes (that represent the operations of the language), add them to the enumerated type in expression.h'. Add support code for these operations in the evaluate_subexp' function defined in the file eval.c'. Add cases for new opcodes in two functions from parse.c': prefixify_subexp' and length_of_subexp'. These compute the number of exp_element's that a given operation takes up. _Update some existing code_ Add an enumerated identifier for your language to the enumerated type enum language' in defs.h'. Update the routines in language.c' so your language is included. These routines include type predicates and such, which (in some cases) are language dependent. If your language does not appear in the switch statement, an error is reported. Also included in language.c' is the code that updates the variable current_language', and the routines that translate the language_LANG' enumerated identifier into a printable string. Update the function _initialize_language' to include your language. This function picks the default language upon startup, so is dependent upon which languages that GDB is built for. Update allocate_symtab' in symfile.c' and/or symbol-reading code so that the language of each symtab (source file) is set properly. This is used to determine the language to use at each stack frame level. Currently, the language is set based upon the extension of the source file. If the language can be better inferred from the symbol information, please set the language of the symtab in the symbol-reading code. Add helper code to print_subexp' (in expprint.c') to handle any new expression opcodes you have added to expression.h'. Also, add the printed representations of your operators to op_print_tab'. _Add a place of call_ Add a call to LANG_parse()' and LANG_error' in parse_exp_1' (defined in parse.c'). _Edit Makefile.in'_ Add dependencies in Makefile.in'. Make sure you update the macro variables such as HFILES' and OBJS', otherwise your code may not get linked in, or, worse yet, it may not get tar'red into the distribution! File: gdbint.info, Node: Host Definition, Next: Target Architecture Definition, Prev: Language Support, Up: Top 10 Host Definition ****************** With the advent of Autoconf, it's rarely necessary to have host definition machinery anymore. The following information is provided, mainly, as an historical reference. 10.1 Adding a New Host ====================== GDB's host configuration support normally happens via Autoconf. New host-specific definitions should not be needed. Older hosts GDB still use the host-specific definitions and files listed below, but these mostly exist for historical reasons, and will eventually disappear. gdb/config/ARCH/XYZ.mh' This file is a Makefile fragment that once contained both host and native configuration information (*note Native Debugging::) for the machine XYZ. The host configuration information is now handled by Autoconf. Host configuration information included definitions for CC', SYSV_DEFINE', XM_CFLAGS', XM_ADD_FILES', XM_CLIBS', XM_CDEPS', etc.; see Makefile.in'. New host-only configurations do not need this file. (Files named gdb/config/ARCH/xm-XYZ.h' were once used to define host-specific macros, but were no longer needed and have all been removed.) Generic Host Support Files -------------------------- There are some "generic" versions of routines that can be used by various systems. ser-unix.c' This contains serial line support for Unix systems. It is included by default on all Unix-like hosts. ser-pipe.c' This contains serial pipe support for Unix systems. It is included by default on all Unix-like hosts. ser-mingw.c' This contains serial line support for 32-bit programs running under Windows using MinGW. ser-go32.c' This contains serial line support for 32-bit programs running under DOS, using the DJGPP (a.k.a. GO32) execution environment. ser-tcp.c' This contains generic TCP support using sockets. It is included by default on all Unix-like hosts and with MinGW. 10.2 Host Conditionals ====================== When GDB is configured and compiled, various macros are defined or left undefined, to control compilation based on the attributes of the host system. While formerly they could be set in host-specific header files, at present they can be changed only by setting CFLAGS' when building, or by editing the source code. These macros and their meanings (or if the meaning is not documented here, then one of the source files where they are used is indicated) are: GDBINIT_FILENAME' The default name of GDB's initialization file (normally .gdbinit'). SIGWINCH_HANDLER' If your host defines SIGWINCH', you can define this to be the name of a function to be called if SIGWINCH' is received. SIGWINCH_HANDLER_BODY' Define this to expand into code that will define the function named by the expansion of SIGWINCH_HANDLER'. CRLF_SOURCE_FILES' Define this if host files use \r\n' rather than \n' as a line terminator. This will cause source file listings to omit \r' characters when printing and it will allow \r\n' line endings of files which are "sourced" by gdb. It must be possible to open files in binary mode using O_BINARY' or, for fopen, "rb"'. DEFAULT_PROMPT' The default value of the prompt string (normally "(gdb) "'). DEV_TTY' The name of the generic TTY device, defaults to "/dev/tty"'. ISATTY' Substitute for isatty, if not available. FOPEN_RB' Define this if binary files are opened the same way as text files. CC_HAS_LONG_LONG' Define this if the host C compiler supports long long'. This is set by the configure' script. PRINTF_HAS_LONG_LONG' Define this if the host can handle printing of long long integers via the printf format conversion specifier ll'. This is set by the configure' script. LSEEK_NOT_LINEAR' Define this if lseek (n)' does not necessarily move to byte number n' in the file. This is only used when reading source files. It is normally faster to define CRLF_SOURCE_FILES' when possible. lint' Define this to help placate lint' in some situations. volatile' Define this to override the defaults of __volatile__' or /**/'. File: gdbint.info, Node: Target Architecture Definition, Next: Target Descriptions, Prev: Host Definition, Up: Top 11 Target Architecture Definition ********************************* GDB's target architecture defines what sort of machine-language programs GDB can work with, and how it works with them. The target architecture object is implemented as the C structure struct gdbarch *'. The structure, and its methods, are generated using the Bourne shell script gdbarch.sh'. * Menu: * OS ABI Variant Handling:: * Initialize New Architecture:: * Registers and Memory:: * Pointers and Addresses:: * Address Classes:: * Register Representation:: * Frame Interpretation:: * Inferior Call Setup:: * Adding support for debugging core files:: * Defining Other Architecture Features:: * Adding a New Target:: File: gdbint.info, Node: OS ABI Variant Handling, Next: Initialize New Architecture, Up: Target Architecture Definition 11.1 Operating System ABI Variant Handling ========================================== GDB provides a mechanism for handling variations in OS ABIs. An OS ABI variant may have influence over any number of variables in the target architecture definition. There are two major components in the OS ABI mechanism: sniffers and handlers. A "sniffer" examines a file matching a BFD architecture/flavour pair (the architecture may be wildcarded) in an attempt to determine the OS ABI of that file. Sniffers with a wildcarded architecture are considered to be "generic", while sniffers for a specific architecture are considered to be "specific". A match from a specific sniffer overrides a match from a generic sniffer. Multiple sniffers for an architecture/flavour may exist, in order to differentiate between two different operating systems which use the same basic file format. The OS ABI framework provides a generic sniffer for ELF-format files which examines the EI_OSABI' field of the ELF header, as well as note sections known to be used by several operating systems. A "handler" is used to fine-tune the gdbarch' structure for the selected OS ABI. There may be only one handler for a given OS ABI for each BFD architecture. The following OS ABI variants are defined in defs.h': GDB_OSABI_UNINITIALIZED' Used for struct gdbarch_info if ABI is still uninitialized. GDB_OSABI_UNKNOWN' The ABI of the inferior is unknown. The default gdbarch' settings for the architecture will be used. GDB_OSABI_SVR4' UNIX System V Release 4. GDB_OSABI_HURD' GNU using the Hurd kernel. GDB_OSABI_SOLARIS' Sun Solaris. GDB_OSABI_OSF1' OSF/1, including Digital UNIX and Compaq Tru64 UNIX. GDB_OSABI_LINUX' GNU using the Linux kernel. GDB_OSABI_FREEBSD_AOUT' FreeBSD using the a.out' executable format. GDB_OSABI_FREEBSD_ELF' FreeBSD using the ELF executable format. GDB_OSABI_NETBSD_AOUT' NetBSD using the a.out' executable format. GDB_OSABI_NETBSD_ELF' NetBSD using the ELF executable format. GDB_OSABI_OPENBSD_ELF' OpenBSD using the ELF executable format. GDB_OSABI_WINCE' Windows CE. GDB_OSABI_GO32' DJGPP. GDB_OSABI_IRIX' Irix. GDB_OSABI_INTERIX' Interix (Posix layer for MS-Windows systems). GDB_OSABI_HPUX_ELF' HP/UX using the ELF executable format. GDB_OSABI_HPUX_SOM' HP/UX using the SOM executable format. GDB_OSABI_QNXNTO' QNX Neutrino. GDB_OSABI_CYGWIN' Cygwin. GDB_OSABI_AIX' AIX. Here are the functions that make up the OS ABI framework: -- Function: const char * gdbarch_osabi_name (enum gdb_osabi OSABI) Return the name of the OS ABI corresponding to OSABI. -- Function: void gdbarch_register_osabi (enum bfd_architecture ARCH, unsigned long MACHINE, enum gdb_osabi OSABI, void (*INIT_OSABI)(struct gdbarch_info INFO, struct gdbarch *GDBARCH)) Register the OS ABI handler specified by INIT_OSABI for the architecture, machine type and OS ABI specified by ARCH, MACHINE and OSABI. In most cases, a value of zero for the machine type, which implies the architecture's default machine type, will suffice. -- Function: void gdbarch_register_osabi_sniffer (enum bfd_architecture ARCH, enum bfd_flavour FLAVOUR, enum gdb_osabi (*SNIFFER)(bfd *ABFD)) Register the OS ABI file sniffer specified by SNIFFER for the BFD architecture/flavour pair specified by ARCH and FLAVOUR. If ARCH is bfd_arch_unknown', the sniffer is considered to be generic, and is allowed to examine FLAVOUR-flavoured files for any architecture. -- Function: enum gdb_osabi gdbarch_lookup_osabi (bfd *ABFD) Examine the file described by ABFD to determine its OS ABI. The value GDB_OSABI_UNKNOWN' is returned if the OS ABI cannot be determined. -- Function: void gdbarch_init_osabi (struct gdbarch info INFO, struct gdbarch *GDBARCH, enum gdb_osabi OSABI) Invoke the OS ABI handler corresponding to OSABI to fine-tune the gdbarch' structure specified by GDBARCH. If a handler corresponding to OSABI has not been registered for GDBARCH's architecture, a warning will be issued and the debugging session will continue with the defaults already established for GDBARCH. -- Function: void generic_elf_osabi_sniff_abi_tag_sections (bfd *ABFD, asection *SECT, void *OBJ) Helper routine for ELF file sniffers. Examine the file described by ABFD and look at ABI tag note sections to determine the OS ABI from the note. This function should be called via bfd_map_over_sections'. File: gdbint.info, Node: Initialize New Architecture, Next: Registers and Memory, Prev: OS ABI Variant Handling, Up: Target Architecture Definition 11.2 Initializing a New Architecture ==================================== * Menu: * How an Architecture is Represented:: * Looking Up an Existing Architecture:: * Creating a New Architecture:: File: gdbint.info, Node: How an Architecture is Represented, Next: Looking Up an Existing Architecture, Up: Initialize New Architecture 11.2.1 How an Architecture is Represented ----------------------------------------- Each gdbarch' is associated with a single BFD architecture, via a bfd_arch_ARCH' in the bfd_architecture' enumeration. The gdbarch' is registered by a call to register_gdbarch_init', usually from the file's _initialize_FILENAME' routine, which will be automatically called during GDB startup. The arguments are a BFD architecture constant and an initialization function. A GDB description for a new architecture, ARCH is created by defining a global function _initialize_ARCH_tdep', by convention in the source file ARCH-tdep.c'. For example, in the case of the OpenRISC 1000, this function is called _initialize_or1k_tdep' and is found in the file or1k-tdep.c'. The resulting object files containing the implementation of the _initialize_ARCH_tdep' function are specified in the GDB configure.tgt' file, which includes a large case statement pattern matching against the --target' option of the configure' script. The new struct gdbarch' is created within the _initialize_ARCH_tdep' function by calling gdbarch_register': void gdbarch_register (enum bfd_architecture ARCHITECTURE, gdbarch_init_ftype *INIT_FUNC, gdbarch_dump_tdep_ftype *TDEP_DUMP_FUNC); The ARCHITECTURE will identify the unique BFD to be associated with this gdbarch'. The INIT_FUNC funciton is called to create and return the new struct gdbarch'. The TDEP_DUMP_FUNC function will dump the target specific details associated with this architecture. For example the function _initialize_or1k_tdep' creates its architecture for 32-bit OpenRISC 1000 architectures by calling: gdbarch_register (bfd_arch_or32, or1k_gdbarch_init, or1k_dump_tdep); File: gdbint.info, Node: Looking Up an Existing Architecture, Next: Creating a New Architecture, Prev: How an Architecture is Represented, Up: Initialize New Architecture 11.2.2 Looking Up an Existing Architecture ------------------------------------------ The initialization function has this prototype: static struct gdbarch * ARCH_gdbarch_init (struct gdbarch_info INFO, struct gdbarch_list *ARCHES) The INFO argument contains parameters used to select the correct architecture, and ARCHES is a list of architectures which have already been created with the same bfd_arch_ARCH' value. The initialization function should first make sure that INFO is acceptable, and return NULL' if it is not. Then, it should search through ARCHES for an exact match to INFO, and return one if found. Lastly, if no exact match was found, it should create a new architecture based on INFO and return it. The lookup is done using gdbarch_list_lookup_by_info'. It is passed the list of existing architectures, ARCHES, and the struct gdbarch_info', INFO, and returns the first matching architecture it finds, or NULL' if none are found. If an architecture is found it can be returned as the result from the initialization function, otherwise a new struct gdbach' will need to be created. The struct gdbarch_info has the following components: struct gdbarch_info { const struct bfd_arch_info *bfd_arch_info; int byte_order; bfd *abfd; struct gdbarch_tdep_info *tdep_info; enum gdb_osabi osabi; const struct target_desc *target_desc; }; The bfd_arch_info' member holds the key details about the architecture. The byte_order' member is a value in an enumeration indicating the endianism. The abfd' member is a pointer to the full BFD, the tdep_info' member is additional custom target specific information, osabi' identifies which (if any) of a number of operating specific ABIs are used by this architecture and the target_desc' member is a set of name-value pairs with information about register usage in this target. When the struct gdbarch' initialization function is called, not all the fields are provided--only those which can be deduced from the BFD. The struct gdbarch_info', INFO is used as a look-up key with the list of existing architectures, ARCHES to see if a suitable architecture already exists. The TDEP_INFO, OSABI and TARGET_DESC fields may be added before this lookup to refine the search. Only information in INFO should be used to choose the new architecture. Historically, INFO could be sparse, and defaults would be collected from the first element on ARCHES. However, GDB now fills in INFO more thoroughly, so new gdbarch' initialization functions should not take defaults from ARCHES. File: gdbint.info, Node: Creating a New Architecture, Prev: Looking Up an Existing Architecture, Up: Initialize New Architecture 11.2.3 Creating a New Architecture ---------------------------------- If no architecture is found, then a new architecture must be created, by calling gdbarch_alloc' using the supplied struct gdbarch_info' and any additional custom target specific information in a struct gdbarch_tdep'. The prototype for gdbarch_alloc' is: struct gdbarch *gdbarch_alloc (const struct gdbarch_info *INFO, struct gdbarch_tdep *TDEP); The newly created struct gdbarch must then be populated. Although there are default values, in most cases they are not what is required. For each element, X, there is are a pair of corresponding accessor functions, one to set the value of that element, set_gdbarch_X', the second to either get the value of an element (if it is a variable) or to apply the element (if it is a function), gdbarch_X'. Note that both accessor functions take a pointer to the struct gdbarch' as first argument. Populating the new gdbarch' should use the set_gdbarch' functions. The following sections identify the main elements that should be set in this way. This is not the complete list, but represents the functions and elements that must commonly be specified for a new architecture. Many of the functions and variables are described in the header file gdbarch.h'. This is the main work in defining a new architecture. Implementing the set of functions to populate the struct gdbarch'. struct gdbarch_tdep' is not defined within GDB--it is up to the user to define this struct if it is needed to hold custom target information that is not covered by the standard struct gdbarch'. For example with the OpenRISC 1000 architecture it is used to hold the number of matchpoints available in the target (along with other information). If there is no additional target specific information, it can be set to NULL'. File: gdbint.info, Node: Registers and Memory, Next: Pointers and Addresses, Prev: Initialize New Architecture, Up: Target Architecture Definition 11.3 Registers and Memory ========================= GDB's model of the target machine is rather simple. GDB assumes the machine includes a bank of registers and a block of memory. Each register may have a different size. GDB does not have a magical way to match up with the compiler's idea of which registers are which; however, it is critical that they do match up accurately. The only way to make this work is to get accurate information about the order that the compiler uses, and to reflect that in the gdbarch_register_name' and related functions. GDB can handle big-endian, little-endian, and bi-endian architectures. File: gdbint.info, Node: Pointers and Addresses, Next: Address Classes, Prev: Registers and Memory, Up: Target Architecture Definition 11.4 Pointers Are Not Always Addresses ====================================== On almost all 32-bit architectures, the representation of a pointer is indistinguishable from the representation of some fixed-length number whose value is the byte address of the object pointed to. On such machines, the words "pointer" and "address" can be used interchangeably. However, architectures with smaller word sizes are often cramped for address space, so they may choose a pointer representation that breaks this identity, and allows a larger code address space. For example, the Renesas D10V is a 16-bit VLIW processor whose instructions are 32 bits long(1). If the D10V used ordinary byte addresses to refer to code locations, then the processor would only be able to address 64kb of instructions. However, since instructions must be aligned on four-byte boundaries, the low two bits of any valid instruction's byte address are always zero--byte addresses waste two bits. So instead of byte addresses, the D10V uses word addresses--byte addresses shifted right two bits--to refer to code. Thus, the D10V can use 16-bit words to address 256kb of code space. However, this means that code pointers and data pointers have different forms on the D10V. The 16-bit word 0xC020' refers to byte address 0xC020' when used as a data address, but refers to byte address 0x30080' when used as a code address. (The D10V also uses separate code and data address spaces, which also affects the correspondence between pointers and addresses, but we're going to ignore that here; this example is already too long.) To cope with architectures like this--the D10V is not the only one!--GDB tries to distinguish between "addresses", which are byte numbers, and "pointers", which are the target's representation of an address of a particular type of data. In the example above, 0xC020' is the pointer, which refers to one of the addresses 0xC020' or 0x30080', depending on the type imposed upon it. GDB provides functions for turning a pointer into an address and vice versa, in the appropriate way for the current architecture. Unfortunately, since addresses and pointers are identical on almost all processors, this distinction tends to bit-rot pretty quickly. Thus, each time you port GDB to an architecture which does distinguish between pointers and addresses, you'll probably need to clean up some architecture-independent code. Here are functions which convert between pointers and addresses: -- Function: CORE_ADDR extract_typed_address (void *BUF, struct type *TYPE) Treat the bytes at BUF as a pointer or reference of type TYPE, and return the address it represents, in a manner appropriate for the current architecture. This yields an address GDB can use to read target memory, disassemble, etc. Note that BUF refers to a buffer in GDB's memory, not the inferior's. For example, if the current architecture is the Intel x86, this function extracts a little-endian integer of the appropriate length from BUF and returns it. However, if the current architecture is the D10V, this function will return a 16-bit integer extracted from BUF, multiplied by four if TYPE is a pointer to a function. If TYPE is not a pointer or reference type, then this function will signal an internal error. -- Function: CORE_ADDR store_typed_address (void *BUF, struct type *TYPE, CORE_ADDR ADDR) Store the address ADDR in BUF, in the proper format for a pointer of type TYPE in the current architecture. Note that BUF refers to a buffer in GDB's memory, not the inferior's. For example, if the current architecture is the Intel x86, this function stores ADDR unmodified as a little-endian integer of the appropriate length in BUF. However, if the current architecture is the D10V, this function divides ADDR by four if TYPE is a pointer to a function, and then stores it in BUF. If TYPE is not a pointer or reference type, then this function will signal an internal error. -- Function: CORE_ADDR value_as_address (struct value *VAL) Assuming that VAL is a pointer, return the address it represents, as appropriate for the current architecture. This function actually works on integral values, as well as pointers. For pointers, it performs architecture-specific conversions as described above for extract_typed_address'. -- Function: CORE_ADDR value_from_pointer (struct type *TYPE, CORE_ADDR ADDR) Create and return a value representing a pointer of type TYPE to the address ADDR, as appropriate for the current architecture. This function performs architecture-specific conversions as described above for store_typed_address'. Here are two functions which architectures can define to indicate the relationship between pointers and addresses. These have default definitions, appropriate for architectures on which all pointers are simple unsigned byte addresses. -- Function: CORE_ADDR gdbarch_pointer_to_address (struct gdbarch *GDBARCH, struct type *TYPE, char *BUF) Assume that BUF holds a pointer of type TYPE, in the appropriate format for the current architecture. Return the byte address the pointer refers to. This function may safely assume that TYPE is either a pointer or a C++ reference type. -- Function: void gdbarch_address_to_pointer (struct gdbarch *GDBARCH, struct type *TYPE, char *BUF, CORE_ADDR ADDR) Store in BUF a pointer of type TYPE representing the address ADDR, in the appropriate format for the current architecture. This function may safely assume that TYPE is either a pointer or a C++ reference type. ---------- Footnotes ---------- (1) Some D10V instructions are actually pairs of 16-bit sub-instructions. However, since you can't jump into the middle of such a pair, code addresses can only refer to full 32 bit instructions, which is what matters in this explanation. File: gdbint.info, Node: Address Classes, Next: Register Representation, Prev: Pointers and Addresses, Up: Target Architecture Definition 11.5 Address Classes ==================== Sometimes information about different kinds of addresses is available via the debug information. For example, some programming environments define addresses of several different sizes. If the debug information distinguishes these kinds of address classes through either the size info (e.g, DW_AT_byte_size' in DWARF 2) or through an explicit address class attribute (e.g, DW_AT_address_class' in DWARF 2), the following macros should be defined in order to disambiguate these types within GDB as well as provide the added information to a GDB user when printing type expressions. -- Function: int gdbarch_address_class_type_flags (struct gdbarch *GDBARCH, int BYTE_SIZE, int DWARF2_ADDR_CLASS) Returns the type flags needed to construct a pointer type whose size is BYTE_SIZE and whose address class is DWARF2_ADDR_CLASS. This function is normally called from within a symbol reader. See dwarf2read.c'. -- Function: char * gdbarch_address_class_type_flags_to_name (struct gdbarch *GDBARCH, int TYPE_FLAGS) Given the type flags representing an address class qualifier, return its name. -- Function: int gdbarch_address_class_name_to_type_flags (struct gdbarch *GDBARCH, int NAME, int *TYPE_FLAGS_PTR) Given an address qualifier name, set the int' referenced by TYPE_FLAGS_PTR to the type flags for that address class qualifier. Since the need for address classes is rather rare, none of the address class functions are defined by default. Predicate functions are provided to detect when they are defined. Consider a hypothetical architecture in which addresses are normally 32-bits wide, but 16-bit addresses are also supported. Furthermore, suppose that the DWARF 2 information for this architecture simply uses a DW_AT_byte_size' value of 2 to indicate the use of one of these "short" pointers. The following functions could be defined to implement the address class functions: somearch_address_class_type_flags (int byte_size, int dwarf2_addr_class) { if (byte_size == 2) return TYPE_FLAG_ADDRESS_CLASS_1; else return 0; } static char * somearch_address_class_type_flags_to_name (int type_flags) { if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1) return "short"; else return NULL; } int somearch_address_class_name_to_type_flags (char *name, int *type_flags_ptr) { if (strcmp (name, "short") == 0) { *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1; return 1; } else return 0; } The qualifier @short' is used in GDB's type expressions to indicate the presence of one of these "short" pointers. For example if the debug information indicates that short_ptr_var' is one of these short pointers, GDB might show the following behavior: (gdb) ptype short_ptr_var type = int * @short File: gdbint.info, Node: Register Representation, Next: Frame Interpretation, Prev: Address Classes, Up: Target Architecture Definition 11.6 Register Representation ============================ * Menu: * Raw and Cooked Registers:: * Register Architecture Functions & Variables:: * Register Information Functions:: * Register and Memory Data:: * Register Caching:: File: gdbint.info, Node: Raw and Cooked Registers, Next: Register Architecture Functions & Variables, Up: Register Representation 11.6.1 Raw and Cooked Registers ------------------------------- GDB considers registers to be a set with members numbered linearly from 0 upwards. The first part of that set corresponds to real physical registers, the second part to any "pseudo-registers". Pseudo-registers have no independent physical existence, but are useful representations of information within the architecture. For example the OpenRISC 1000 architecture has up to 32 general purpose registers, which are typically represented as 32-bit (or 64-bit) integers. However the GPRs are also used as operands to the floating point operations, and it could be convenient to define a set of pseudo-registers, to show the GPRs represented as floating point values. For any architecture, the implementer will decide on a mapping from hardware to GDB register numbers. The registers corresponding to real hardware are referred to as "raw" registers, the remaining registers are "pseudo-registers". The total register set (raw and pseudo) is called the "cooked" register set. File: gdbint.info, Node: Register Architecture Functions & Variables, Next: Register Information Functions, Prev: Raw and Cooked Registers, Up: Register Representation 11.6.2 Functions and Variables Specifying the Register Architecture ------------------------------------------------------------------- These struct gdbarch' functions and variables specify the number and type of registers in the architecture. -- Architecture Function: CORE_ADDR read_pc (struct regcache *REGCACHE) -- Architecture Function: void write_pc (struct regcache *REGCACHE, CORE_ADDR VAL) Read or write the program counter. The default value of both functions is NULL' (no function available). If the program counter is just an ordinary register, it can be specified in struct gdbarch' instead (see pc_regnum' below) and it will be read or written using the standard routines to access registers. This function need only be specified if the program counter is not an ordinary register. Any register information can be obtained using the supplied register cache, REGCACHE. *Note Register Caching: Register Caching. -- Architecture Function: void pseudo_register_read (struct gdbarch *GDBARCH, struct regcache *REGCACHE, int REGNUM, const gdb_byte *BUF) -- Architecture Function: void pseudo_register_write (struct gdbarch *GDBARCH, struct regcache *REGCACHE, int REGNUM, const gdb_byte *BUF) These functions should be defined if there are any pseudo-registers. The default value is NULL'. REGNUM is the number of the register to read or write (which will be a "cooked" register number) and BUF is the buffer where the value read will be placed, or from which the value to be written will be taken. The value in the buffer may be converted to or from a signed or unsigned integral value using one of the utility functions (*note Using Different Register and Memory Data Representations: Register and Memory Data.). The access should be for the specified architecture, GDBARCH. Any register information can be obtained using the supplied register cache, REGCACHE. *Note Register Caching: Register Caching. -- Architecture Variable: int sp_regnum This specifies the register holding the stack pointer, which may be a raw or pseudo-register. It defaults to -1 (not defined), but it is an error for it not to be defined. The value of the stack pointer register can be accessed withing GDB as the variable sp'.

-- Architecture Variable: int pc_regnum
This specifies the register holding the program counter, which may
be a raw or pseudo-register.  It defaults to -1 (not defined).  If
pc_regnum' is not defined, then the functions read_pc' and
write_pc' (see above) must be defined.

The value of the program counter (whether defined as a register, or
through read_pc' and write_pc') can be accessed withing GDB as
the variable $pc'. -- Architecture Variable: int ps_regnum This specifies the register holding the processor status (often called the status register), which may be a raw or pseudo-register. It defaults to -1 (not defined). If defined, the value of this register can be accessed withing GDB as the variable $ps'.

-- Architecture Variable: int fp0_regnum
This specifies the first floating point register.  It defaults to
0.  fp0_regnum' is not needed unless the target offers support
for floating point.

File: gdbint.info,  Node: Register Information Functions,  Next: Register and Memory Data,  Prev: Register Architecture Functions & Variables,  Up: Register Representation

11.6.3 Functions Giving Register Information
--------------------------------------------

These functions return information about registers.

-- Architecture Function: const char * register_name (struct gdbarch
*GDBARCH, int REGNUM)
This function should convert a register number (raw or pseudo) to a
register name (as a C const char *').  This is used both to
determine the name of a register for output and to work out the
meaning of any register names used as input.  The function may
also return NULL', to indicate that REGNUM is not a valid
register.

For example with the OpenRISC 1000, GDB registers 0-31 are the
General Purpose Registers, register 32 is the program counter and
register 33 is the supervision register (i.e. the processor status
register), which map to the strings "gpr00"' through "gpr31"',
"pc"' and "sr"' respectively. This means that the GDB command
print $gpr5' should print the value of the OR1K general purpose register 5(1). The default value for this function is NULL', meaning undefined. It should always be defined. The access should be for the specified architecture, GDBARCH. -- Architecture Function: struct type * register_type (struct gdbarch *GDBARCH, int REGNUM) Given a register number, this function identifies the type of data it may be holding, specified as a struct type'. GDB allows creation of arbitrary types, but a number of built in types are provided (builtin_type_void', builtin_type_int32' etc), together with functions to derive types from these. Typically the program counter will have a type of "pointer to function" (it points to code), the frame pointer and stack pointer will have types of "pointer to void" (they point to data on the stack) and all other integer registers will have a type of 32-bit integer or 64-bit integer. This information guides the formatting when displaying register information. The default value is NULL' meaning no information is available to guide formatting when displaying registers. -- Architecture Function: void print_registers_info (struct gdbarch *GDBARCH, struct ui_file *FILE, struct frame_info *FRAME, int REGNUM, int ALL) Define this function to print out one or all of the registers for the GDB info registers' command. The default value is the function default_print_registers_info', which uses the register type information (see register_type' above) to determine how each register should be printed. Define a custom version of this function for fuller control over how the registers are displayed. The access should be for the specified architecture, GDBARCH, with output to the the file specified by the User Interface Independent Output file handle, FILE (*note UI-Independent Output--the ui_out' Functions: UI-Independent Output.). The registers should show their values in the frame specified by FRAME. If REGNUM is -1 and ALL is zero, then all the "significant" registers should be shown (the implementer should decide which registers are "significant"). Otherwise only the value of the register specified by REGNUM should be output. If REGNUM is -1 and ALL is non-zero (true), then the value of all registers should be shown. By default default_print_registers_info' prints one register per line, and if ALL is zero omits floating-point registers. -- Architecture Function: void print_float_info (struct gdbarch *GDBARCH, struct ui_file *FILE, struct frame_info *FRAME, const char *ARGS) Define this function to provide output about the floating point unit and registers for the GDB info float' command respectively. The default value is NULL' (not defined), meaning no information will be provided. The GDBARCH and FILE and FRAME arguments have the same meaning as in the print_registers_info' function above. The string ARGS contains any supplementary arguments to the info float' command. Define this function if the target supports floating point operations. -- Architecture Function: void print_vector_info (struct gdbarch *GDBARCH, struct ui_file *FILE, struct frame_info *FRAME, const char *ARGS) Define this function to provide output about the vector unit and registers for the GDB info vector' command respectively. The default value is NULL' (not defined), meaning no information will be provided. The GDBARCH, FILE and FRAME arguments have the same meaning as in the print_registers_info' function above. The string ARGS contains any supplementary arguments to the info vector' command. Define this function if the target supports vector operations. -- Architecture Function: int register_reggroup_p (struct gdbarch *GDBARCH, int REGNUM, struct reggroup *GROUP) GDB groups registers into different categories (general, vector, floating point etc). This function, given a register, REGNUM, and group, GROUP, returns 1 (true) if the register is in the group and 0 (false) otherwise. The information should be for the specified architecture, GDBARCH The default value is the function default_register_reggroup_p' which will do a reasonable job based on the type of the register (see the function register_type' above), with groups for general purpose registers, floating point registers, vector registers and raw (i.e not pseudo) registers. ---------- Footnotes ---------- (1) Historically, GDB always had a concept of a frame pointer register, which could be accessed via the GDB variable, $fp'.  That
concept is now deprecated, recognizing that not all architectures have
a frame pointer.  However if an architecture does have a frame pointer
register, and defines a register or pseudo-register with the name
"fp"', then that register will be used as the value of the fp' variable. File: gdbint.info, Node: Register and Memory Data, Next: Register Caching, Prev: Register Information Functions, Up: Register Representation 11.6.4 Using Different Register and Memory Data Representations --------------------------------------------------------------- Some architectures have different representations of data objects, depending whether the object is held in a register or memory. For example: * The Alpha architecture can represent 32 bit integer values in floating-point registers. * The x86 architecture supports 80-bit floating-point registers. The long double' data type occupies 96 bits in memory but only 80 bits when stored in a register. In general, the register representation of a data type is determined by the architecture, or GDB's interface to the architecture, while the memory representation is determined by the Application Binary Interface. For almost all data types on almost all architectures, the two representations are identical, and no special handling is needed. However, they do occasionally differ. An architecture may define the following struct gdbarch' functions to request conversions between the register and memory representations of a data type: -- Architecture Function: int gdbarch_convert_register_p (struct gdbarch *GDBARCH, int REG) Return non-zero (true) if the representation of a data value stored in this register may be different to the representation of that same data value when stored in memory. The default value is NULL' (undefined). If this function is defined and returns non-zero, the struct gdbarch' functions gdbarch_register_to_value' and gdbarch_value_to_register' (see below) should be used to perform any necessary conversion. If defined, this function should return zero for the register's native type, when no conversion is necessary. -- Architecture Function: void gdbarch_register_to_value (struct gdbarch *GDBARCH, int REG, struct type *TYPE, char *FROM, char *TO) Convert the value of register number REG to a data object of type TYPE. The buffer at FROM holds the register's value in raw format; the converted value should be placed in the buffer at TO. _Note:_ gdbarch_register_to_value' and gdbarch_value_to_register' take their REG and TYPE arguments in different orders. gdbarch_register_to_value' should only be used with registers for which the gdbarch_convert_register_p' function returns a non-zero value. -- Architecture Function: void gdbarch_value_to_register (struct gdbarch *GDBARCH, struct type *TYPE, int REG, char *FROM, char *TO) Convert a data value of type TYPE to register number REG' raw format. _Note:_ gdbarch_register_to_value' and gdbarch_value_to_register' take their REG and TYPE arguments in different orders. gdbarch_value_to_register' should only be used with registers for which the gdbarch_convert_register_p' function returns a non-zero value. File: gdbint.info, Node: Register Caching, Prev: Register and Memory Data, Up: Register Representation 11.6.5 Register Caching ----------------------- Caching of registers is used, so that the target does not need to be accessed and reanalyzed multiple times for each register in circumstances where the register value cannot have changed. GDB provides struct regcache', associated with a particular struct gdbarch' to hold the cached values of the raw registers. A set of functions is provided to access both the raw registers (with raw' in their name) and the full set of cooked registers (with cooked' in their name). Functions are provided to ensure the register cache is kept synchronized with the values of the actual registers in the target. Accessing registers through the struct regcache' routines will ensure that the appropriate struct gdbarch' functions are called when necessary to access the underlying target architecture. In general users should use the "cooked" functions, since these will map to the "raw" functions automatically as appropriate. The two key functions are regcache_cooked_read' and regcache_cooked_write' which read or write a register from or to a byte buffer (type gdb_byte *'). For convenience the wrapper functions regcache_cooked_read_signed', regcache_cooked_read_unsigned', regcache_cooked_write_signed' and regcache_cooked_write_unsigned' are provided, which read or write the value using the buffer and convert to or from an integral value as appropriate. File: gdbint.info, Node: Frame Interpretation, Next: Inferior Call Setup, Prev: Register Representation, Up: Target Architecture Definition 11.7 Frame Interpretation ========================= * Menu: * All About Stack Frames:: * Frame Handling Terminology:: * Prologue Caches:: * Functions and Variable to Analyze Frames:: * Functions to Access Frame Data:: * Analyzing Stacks---Frame Sniffers:: File: gdbint.info, Node: All About Stack Frames, Next: Frame Handling Terminology, Up: Frame Interpretation 11.7.1 All About Stack Frames ----------------------------- GDB needs to understand the stack on which local (automatic) variables are stored. The area of the stack containing all the local variables for a function invocation is known as the "stack frame" for that function (or colloquially just as the "frame"). In turn the function that called the function will have its stack frame, and so on back through the chain of functions that have been called. Almost all architectures have one register dedicated to point to the end of the stack (the "stack pointer"). Many have a second register which points to the start of the currently active stack frame (the "frame pointer"). The specific arrangements for an architecture are a key part of the ABI. A diagram helps to explain this. Here is a simple program to compute factorials: #include <stdio.h> int fact (int n) { if (0 == n) { return 1; } else { return n * fact (n - 1); } } main () { int i; for (i = 0; i < 10; i++) { int f = fact (i); printf ("%d! = %d\n", i, f); } } Consider the state of the stack when the code reaches line 6 after the main program has called fact (3)'. The chain of function calls will be main ()', fact (3)', fact (2)', fact (1)' and fact (0)'. In this illustration the stack is falling (as used for example by the OpenRISC 1000 ABI). The stack pointer (SP) is at the end of the stack (lowest address) and the frame pointer (FP) is at the highest address in the current stack frame. The following diagram shows how the stack looks. ^ ->| | Frame | | | | Number - | | |============| int fact (int n) | | | | i = 3 | { | | | |------------| if (0 == n) { | | | | f = ? | return 1; <-------- PC #4 main() < | | |------------| } | | | | | else { | | -+->|------------| ---> return n * fact (n - 1); | -+-+--+-----o | | } = | | |============| | } | | | | n = 3 | | | | | |------------| | main () #3 fact (3) < | | | o---------+- { | -+-+->|------------| | | int i; | | | --+-----o | | | = | | |============| | | for (i = 0; i < 10; i++) { | | | | n = 2 | | -> int f = fact (i); | | | |------------| | printf ("%d! = %d\n", i , f); #2 fact (2) < | | | o------+--| } | | | ->|------------| | } | | -+--+-----o | | = | | |============| | | | | | n = 1 | | | | | |------------| | #1 fact (1) < | | | o------+--| | | | |------------| | | ---|--+-----o |<-+------- FP = | |============| | | | | | n = 0 | | | | | |------------| | | #0 fact (0) < | | o--------- | | | |------------| | | --+-----o |<--------- SP | = |============| | | | Red Zone | v | \/\/\/\/\/\/\/ Direction of #-1 < \/\/\/\/\/\/\/ stack growth | | | In each stack frame, offset 0 from the stack pointer is the frame pointer of the previous frame and offset 4 (this is illustrating a 32-bit architecture) from the stack pointer is the return address. Local variables are indexed from the frame pointer, with negative indexes. In the function fact', offset -4 from the frame pointer is the argument N. In the main' function, offset -4 from the frame pointer is the local variable I and offset -8 from the frame pointer is the local variable F(1). It is very easy to get confused when examining stacks. GDB has terminology it uses rigorously throughout. The stack frame of the function currently executing, or where execution stopped is numbered zero. In this example frame #0 is the stack frame of the call to fact (0)'. The stack frame of its calling function (fact (1)' in this case) is numbered #1 and so on back through the chain of calls. The main GDB data structure describing frames is struct frame_info'. It is not used directly, but only via its accessor functions. frame_info' includes information about the registers in the frame and a pointer to the code of the function with which the frame is associated. The entire stack is represented as a linked list of frame_info' structs. ---------- Footnotes ---------- (1) This is a simplified example for illustrative purposes only. Good optimizing compilers would not put anything on the stack for such simple functions. Indeed they might eliminate the recursion and use of the stack entirely! File: gdbint.info, Node: Frame Handling Terminology, Next: Prologue Caches, Prev: All About Stack Frames, Up: Frame Interpretation 11.7.2 Frame Handling Terminology --------------------------------- It is easy to get confused when referencing stack frames. GDB uses some precise terminology. * "THIS" frame is the frame currently under consideration. * The "NEXT" frame, also sometimes called the inner or newer frame is the frame of the function called by the function of THIS frame. * The "PREVIOUS" frame, also sometimes called the outer or older frame is the frame of the function which called the function of THIS frame. So in the example in the previous section (*note All About Stack Frames: All About Stack Frames.), if THIS frame is #3 (the call to fact (3)'), the NEXT frame is frame #2 (the call to fact (2)') and the PREVIOUS frame is frame #4 (the call to main ()'). The "innermost" frame is the frame of the current executing function, or where the program stopped, in this example, in the middle of the call to fact (0))'. It is always numbered frame #0. The "base" of a frame is the address immediately before the start of the NEXT frame. For a stack which grows down in memory (a "falling" stack) this will be the lowest address and for a stack which grows up in memory (a "rising" stack) this will be the highest address in the frame. GDB functions to analyze the stack are typically given a pointer to the NEXT frame to determine information about THIS frame. Information about THIS frame includes data on where the registers of the PREVIOUS frame are stored in this stack frame. In this example the frame pointer of the PREVIOUS frame is stored at offset 0 from the stack pointer of THIS frame. The process whereby a function is given a pointer to the NEXT frame to work out information about THIS frame is referred to as "unwinding". The GDB functions involved in this typically include unwind in their name. The process of analyzing a target to determine the information that should go in struct frame_info is called "sniffing". The functions that carry this out are called sniffers and typically include sniffer in their name. More than one sniffer may be required to extract all the information for a particular frame. Because so many functions work using the NEXT frame, there is an issue about addressing the innermost frame--it has no NEXT frame. To solve this GDB creates a dummy frame #-1, known as the "sentinel" frame. File: gdbint.info, Node: Prologue Caches, Next: Functions and Variable to Analyze Frames, Prev: Frame Handling Terminology, Up: Frame Interpretation 11.7.3 Prologue Caches ---------------------- All the frame sniffing functions typically examine the code at the start of the corresponding function, to determine the state of registers. The ABI will save old values and set new values of key registers at the start of each function in what is known as the function "prologue". For any particular stack frame this data does not change, so all the standard unwinding functions, in addition to receiving a pointer to the NEXT frame as their first argument, receive a pointer to a "prologue cache" as their second argument. This can be used to store values associated with a particular frame, for reuse on subsequent calls involving the same frame. It is up to the user to define the structure used (it is a void *' pointer) and arrange allocation and deallocation of storage. However for general use, GDB provides struct trad_frame_cache', with a set of accessor routines. This structure holds the stack and code address of THIS frame, the base address of the frame, a pointer to the struct frame_info' for the NEXT frame and details of where the registers of the PREVIOUS frame may be found in THIS frame. Typically the first time any sniffer function is called with NEXT frame, the prologue sniffer for THIS frame will be NULL'. The sniffer will analyze the frame, allocate a prologue cache structure and populate it. Subsequent calls using the same NEXT frame will pass in this prologue cache, so the data can be returned with no additional analysis. File: gdbint.info, Node: Functions and Variable to Analyze Frames, Next: Functions to Access Frame Data, Prev: Prologue Caches, Up: Frame Interpretation 11.7.4 Functions and Variable to Analyze Frames ----------------------------------------------- These struct gdbarch' functions and variable should be defined to provide analysis of the stack frame and allow it to be adjusted as required. -- Architecture Function: CORE_ADDR skip_prologue (struct gdbarch *GDBARCH, CORE_ADDR PC) The prologue of a function is the code at the beginning of the function which sets up the stack frame, saves the return address etc. The code representing the behavior of the function starts after the prologue. This function skips past the prologue of a function if the program counter, PC, is within the prologue of a function. The result is the program counter immediately after the prologue. With modern optimizing compilers, this may be a far from trivial exercise. However the required information may be within the binary as DWARF2 debugging information, making the job much easier. The default value is NULL' (not defined). This function should always be provided, but can take advantage of DWARF2 debugging information, if that is available. -- Architecture Function: int inner_than (CORE_ADDR LHS, CORE_ADDR RHS) Given two frame or stack pointers, return non-zero (true) if the first represents the "inner" stack frame and 0 (false) otherwise. This is used to determine whether the target has a stack which grows up in memory (rising stack) or grows down in memory (falling stack). *Note All About Stack Frames: All About Stack Frames, for an explanation of "inner" frames. The default value of this function is NULL' and it should always be defined. However for almost all architectures one of the built-in functions can be used: core_addr_lessthan' (for stacks growing down in memory) or core_addr_greaterthan' (for stacks growing up in memory). -- Architecture Function: CORE_ADDR frame_align (struct gdbarch *GDBARCH, CORE_ADDR ADDRESS) The architecture may have constraints on how its frames are aligned. For example the OpenRISC 1000 ABI requires stack frames to be double-word aligned, but 32-bit versions of the architecture allocate single-word values to the stack. Thus extra padding may be needed at the end of a stack frame. Given a proposed address for the stack pointer, this function returns a suitably aligned address (by expanding the stack frame). The default value is NULL' (undefined). This function should be defined for any architecture where it is possible the stack could become misaligned. The utility functions align_down' (for falling stacks) and align_up' (for rising stacks) will facilitate the implementation of this function. -- Architecture Variable: int frame_red_zone_size Some ABIs reserve space beyond the end of the stack for use by leaf functions without prologue or epilogue or by exception handlers (for example the OpenRISC 1000). This is known as a "red zone" (AMD terminology). The AMD64 (nee x86-64) ABI documentation refers to the "red zone" when describing this scratch area. The default value is 0. Set this field if the architecture has such a red zone. The value must be aligned as required by the ABI (see frame_align' above for an explanation of stack frame alignment). File: gdbint.info, Node: Functions to Access Frame Data, Next: Analyzing Stacks---Frame Sniffers, Prev: Functions and Variable to Analyze Frames, Up: Frame Interpretation 11.7.5 Functions to Access Frame Data ------------------------------------- These functions provide access to key registers and arguments in the stack frame. -- Architecture Function: CORE_ADDR unwind_pc (struct gdbarch *GDBARCH, struct frame_info *NEXT_FRAME) This function is given a pointer to the NEXT stack frame (*note All About Stack Frames: All About Stack Frames, for how frames are represented) and returns the value of the program counter in the PREVIOUS frame (i.e. the frame of the function that called THIS one). This is commonly referred to as the "return address". The implementation, which must be frame agnostic (work with any frame), is typically no more than: ULONGEST pc; pc = frame_unwind_register_unsigned (next_frame, ARCH_PC_REGNUM); return gdbarch_addr_bits_remove (gdbarch, pc); -- Architecture Function: CORE_ADDR unwind_sp (struct gdbarch *GDBARCH, struct frame_info *NEXT_FRAME) This function is given a pointer to the NEXT stack frame (*note All About Stack Frames: All About Stack Frames. for how frames are represented) and returns the value of the stack pointer in the PREVIOUS frame (i.e. the frame of the function that called THIS one). The implementation, which must be frame agnostic (work with any frame), is typically no more than: ULONGEST sp; sp = frame_unwind_register_unsigned (next_frame, ARCH_SP_REGNUM); return gdbarch_addr_bits_remove (gdbarch, sp); -- Architecture Function: int frame_num_args (struct gdbarch *GDBARCH, struct frame_info *THIS_FRAME) This function is given a pointer to THIS stack frame (*note All About Stack Frames: All About Stack Frames. for how frames are represented), and returns the number of arguments that are being passed, or -1 if not known. The default value is NULL' (undefined), in which case the number of arguments passed on any stack frame is always unknown. For many architectures this will be a suitable default. File: gdbint.info, Node: Analyzing Stacks---Frame Sniffers, Prev: Functions to Access Frame Data, Up: Frame Interpretation 11.7.6 Analyzing Stacks--Frame Sniffers --------------------------------------- When a program stops, GDB needs to construct the chain of struct frame_info' representing the state of the stack using appropriate "sniffers". Each architecture requires appropriate sniffers, but they do not form entries in struct gdbarch', since more than one sniffer may be required and a sniffer may be suitable for more than one struct gdbarch'. Instead sniffers are associated with architectures using the following functions. * frame_unwind_append_sniffer' is used to add a new sniffer to analyze THIS frame when given a pointer to the NEXT frame. * frame_base_append_sniffer' is used to add a new sniffer which can determine information about the base of a stack frame. * frame_base_set_default' is used to specify the default base sniffer. These functions all take a reference to struct gdbarch', so they are associated with a specific architecture. They are usually called in the gdbarch' initialization function, after the gdbarch' struct has been set up. Unless a default has been set, the most recently appended sniffer will be tried first. The main frame unwinding sniffer (as set by frame_unwind_append_sniffer)' returns a structure specifying a set of sniffing functions: struct frame_unwind { enum frame_type type; frame_this_id_ftype *this_id; frame_prev_register_ftype *prev_register; const struct frame_data *unwind_data; frame_sniffer_ftype *sniffer; frame_prev_pc_ftype *prev_pc; frame_dealloc_cache_ftype *dealloc_cache; }; The type' field indicates the type of frame this sniffer can handle: normal, dummy (*note Functions Creating Dummy Frames: Functions Creating Dummy Frames.), signal handler or sentinel. Signal handlers sometimes have their own simplified stack structure for efficiency, so may need their own handlers. The unwind_data' field holds additional information which may be relevant to particular types of frame. For example it may hold additional information for signal handler frames. The remaining fields define functions that yield different types of information when given a pointer to the NEXT stack frame. Not all functions need be provided. If an entry is NULL', the next sniffer will be tried instead. * this_id' determines the stack pointer and function (code entry point) for THIS stack frame. * prev_register' determines where the values of registers for the PREVIOUS stack frame are stored in THIS stack frame. * sniffer' takes a look at THIS frame's registers to determine if this is the appropriate unwinder. * prev_pc' determines the program counter for THIS frame. Only needed if the program counter is not an ordinary register (*note Functions and Variables Specifying the Register Architecture: Register Architecture Functions & Variables.). * dealloc_cache' frees any additional memory associated with the prologue cache for this frame (*note Prologue Caches: Prologue Caches.). In general it is only the this_id' and prev_register' fields that need be defined for custom sniffers. The frame base sniffer is much simpler. It is a struct frame_base', which refers to the corresponding frame_unwind' struct and whose fields refer to functions yielding various addresses within the frame. struct frame_base { const struct frame_unwind *unwind; frame_this_base_ftype *this_base; frame_this_locals_ftype *this_locals; frame_this_args_ftype *this_args; }; All the functions referred to take a pointer to the NEXT frame as argument. The function referred to by this_base' returns the base address of THIS frame, the function referred to by this_locals' returns the base address of local variables in THIS frame and the function referred to by this_args' returns the base address of the function arguments in this frame. As described above, the base address of a frame is the address immediately before the start of the NEXT frame. For a falling stack, this is the lowest address in the frame and for a rising stack it is the highest address in the frame. For most architectures the same address is also the base address for local variables and arguments, in which case the same function can be used for all three entries(1). ---------- Footnotes ---------- (1) It is worth noting that if it cannot be determined in any other way (for example by there being a register with the name "fp"'), then the result of the this_base' function will be used as the value of the frame pointer variable fp' in GDB.  This is very often not correct
(for example with the OpenRISC 1000, this value is the stack pointer,
$sp'). In this case a register (raw or pseudo) with the name "fp"' should be defined. It will be used in preference as the value of $fp'.

File: gdbint.info,  Node: Inferior Call Setup,  Next: Adding support for debugging core files,  Prev: Frame Interpretation,  Up: Target Architecture Definition

11.8 Inferior Call Setup
========================

* Functions Creating Dummy Frames::

File: gdbint.info,  Node: About Dummy Frames,  Next: Functions Creating Dummy Frames,  Up: Inferior Call Setup

-------------------------

GDB can call functions in the target code (for example by using the
call' or print' commands).  These functions may be breakpointed, and
it is essential that if a function does hit a breakpoint, commands like
backtrace' work correctly.

This is achieved by making the stack look as though the function had
been called from the point where GDB had previously stopped.  This
requires that GDB can set up stack frames appropriate for such function
calls.

File: gdbint.info,  Node: Functions Creating Dummy Frames,  Prev: About Dummy Frames,  Up: Inferior Call Setup

11.8.2 Functions Creating Dummy Frames
--------------------------------------

The following functions provide the functionality to set up such
"dummy" stack frames.

-- Architecture Function: CORE_ADDR push_dummy_call (struct gdbarch
*GDBARCH, struct value *FUNCTION, struct regcache *REGCACHE,
This function sets up a dummy stack frame for the function about
to be called.  push_dummy_call' is given the arguments to be
passed and must copy them into registers or push them on to the
stack as appropriate for the ABI.

FUNCTION is a pointer to the function that will be called and
REGCACHE the register cache from which values should be obtained.
is breakpointed, so GDB can regain control, hence the name).
NARGS is the number of arguments to pass and ARGS an array
containing the argument values.  STRUCT_RETURN is non-zero (true)
if the function returns a structure, and if so STRUCT_ADDR is the
address in which the structure should be returned.

After calling this function, GDB will pass control to the target
at the address of the function, which will find the stack and
registers set up just as expected.

The default value of this function is NULL' (undefined).  If the
function is not defined, then GDB will not allow the user to call
functions within the target being debugged.

-- Architecture Function: struct frame_id unwind_dummy_id (struct
gdbarch *GDBARCH, struct frame_info *NEXT_FRAME)
This is the inverse of push_dummy_call' which restores the stack
pointer and program counter after a call to evaluate a function
using a dummy stack frame.  The result is a struct frame_id',
which contains the value of the stack pointer and program counter
to be used.

The NEXT frame pointer is provided as argument, NEXT_FRAME.  THIS
frame is the frame of the dummy function, which can be unwound, to
yield the required stack pointer and program counter from the
PREVIOUS frame.

The default value is NULL' (undefined).  If push_dummy_call' is
defined, then this function should also be defined.

-- Architecture Function: CORE_ADDR push_dummy_code (struct gdbarch
**ARGS, int NARGS, struct type *VALUE_TYPE, CORE_ADDR
If this function is not defined (its default value is NULL'), a
dummy call will use the entry point of the currently loaded code
on the target as its return address.  A temporary breakpoint will
be set there, so the location must be writable and have room for a
breakpoint.

It is possible that this default is not suitable.  It might not be
writable (in ROM possibly), or the ABI might require code to be
executed on return from a call to unwind the stack before the
breakpoint is encountered.

If either of these is the case, then push_dummy_code should be
defined to push an instruction sequence onto the end of the stack
to which the dummy call should return.

The arguments are essentially the same as those to
push_dummy_call'.  However the function is provided with the type
of the function result, VALUE_TYPE, BP_ADDR is used to return a
value (the address at which the breakpoint instruction should be
inserted) and REAL PC is used to specify the resume address when
starting the call sequence.  The function should return the

_Note:_ This does require that code in the stack can be
executed.  Some Harvard architectures may not allow this.

File: gdbint.info,  Node: Adding support for debugging core files,  Next: Defining Other Architecture Features,  Prev: Inferior Call Setup,  Up: Target Architecture Definition

11.9 Adding support for debugging core files
============================================

The prerequisite for adding core file support in GDB is to have core
file support in BFD.

Once BFD support is available, writing the apropriate
regset_from_core_section' architecture function should be all that is
needed in order to add support for core files in GDB.

File: gdbint.info,  Node: Defining Other Architecture Features,  Next: Adding a New Target,  Prev: Adding support for debugging core files,  Up: Target Architecture Definition

11.10 Defining Other Architecture Features
==========================================

This section describes other functions and values in gdbarch',
together with some useful macros, that you can use to define the target
architecture.

If a raw machine instruction address includes any bits that are not
really part of the address, then this function is used to zero
instructions, and even then not in all contexts.

For example, the two low-order bits of the PC on the
Hewlett-Packard PA 2.0 architecture contain the privilege level of
the corresponding instruction.  Since instructions must always be
aligned on four-byte boundaries, the processor masks out these
bits to generate the actual address of the instruction.
gdbarch_addr_bits_remove' would then for example look like that:
{
}

If NAME is a valid address class qualifier name, set the int'
referenced by TYPE_FLAGS_PTR to the mask representing the qualifier
and return 1.  If NAME is not a valid address class qualifier name,
return 0.

The value for TYPE_FLAGS_PTR should be one of
TYPE_FLAG_ADDRESS_CLASS_1', TYPE_FLAG_ADDRESS_CLASS_2', or
possibly some combination of these values or'd together.  *Note

Predicate which indicates whether
address_class_name_to_type_flags' has been defined.

Given a pointers byte size (as described by the debug information)
and the possible DW_AT_address_class' value, return the type flags
used by GDB to represent this address class.  The value returned
TYPE_FLAG_ADDRESS_CLASS_2', or possibly some combination of these
values or'd together.  *Note Address Classes: Target Architecture
Definition.

Predicate which indicates whether
gdbarch_address_class_type_flags_p' has been defined.

Return the name of the address class qualifier associated with the
type flags given by TYPE_FLAGS.

int gdbarch_address_class_type_flags_to_name_p (GDBARCH)'
Predicate which indicates whether
*Note Address Classes: Target Architecture Definition.

void gdbarch_address_to_pointer (GDBARCH, TYPE, BUF, ADDR)'
Store in BUF a pointer of type TYPE representing the address ADDR,
in the appropriate format for the current architecture.  This
function may safely assume that TYPE is either a pointer or a C++
reference type.  *Note Pointers Are Not Always Addresses: Target
Architecture Definition.

int gdbarch_believe_pcc_promotion (GDBARCH)'
Used to notify if the compiler promotes a short' or char'
parameter to an int', but still reports the parameter as its
original type, rather than the promoted type.

gdbarch_bits_big_endian (GDBARCH)'
This is used if the numbering of bits in the targets does *not*
match the endianism of the target byte order.  A value of 1 means
that the bits are numbered in a big-endian bit order, 0 means
little-endian.

set_gdbarch_bits_big_endian (GDBARCH, BITS_BIG_ENDIAN)'
Calling set_gdbarch_bits_big_endian with a value of 1 indicates
that the bits in the target are numbered in a big-endian bit
order, 0 indicates little-endian.

BREAKPOINT'
This is the character array initializer for the bit pattern to put
into memory where a breakpoint is set.  Although it's common to
use a trap instruction for a breakpoint, it's not required; for
instance, the bit pattern could be an invalid instruction.  The
breakpoint must be no longer than the shortest instruction of the
architecture.

BREAKPOINT' has been deprecated in favor of
gdbarch_breakpoint_from_pc'.

BIG_BREAKPOINT'
LITTLE_BREAKPOINT'
Similar to BREAKPOINT, but used for bi-endian targets.

BIG_BREAKPOINT' and LITTLE_BREAKPOINT' have been deprecated in
favor of gdbarch_breakpoint_from_pc'.

const gdb_byte *gdbarch_breakpoint_from_pc (GDBARCH, PCPTR, LENPTR)'
Use the program counter to determine the contents and size of a
breakpoint instruction.  It returns a pointer to a static string
of bytes that encode a breakpoint instruction, stores the length
of the string to *LENPTR', and adjusts the program counter (if
necessary) to point to the actual memory location where the
breakpoint should be inserted.  May return NULL' to indicate that
software breakpoints are not supported.

Although it is common to use a trap instruction for a breakpoint,
it's not required; for instance, the bit pattern could be an
invalid instruction.  The breakpoint must be no longer than the
shortest instruction of the architecture.

Provided breakpoint bytes can be also used by
bp_loc_is_permanent' to detect permanent breakpoints.
gdbarch_breakpoint_from_pc' should return an unchanged memory
copy if it was called for a location with permanent breakpoint as
some architectures use breakpoint instructions containing
arbitrary parameter value.

Replaces all the other BREAKPOINT macros.

int gdbarch_memory_insert_breakpoint (GDBARCH, BP_TGT)'
gdbarch_memory_remove_breakpoint (GDBARCH, BP_TGT)'
Insert or remove memory based breakpoints.  Reasonable defaults
(default_memory_insert_breakpoint' and
default_memory_remove_breakpoint' respectively) have been
provided so that it is not necessary to set these for most
architectures.  Architectures which may want to set
gdbarch_memory_insert_breakpoint' and
gdbarch_memory_remove_breakpoint' will likely have instructions
that are oddly sized or are not stored in a conventional manner.

It may also be desirable (from an efficiency standpoint) to define
custom breakpoint insertion and removal routines if
gdbarch_breakpoint_from_pc' needs to read the target's memory for
some reason.

Given an address at which a breakpoint is desired, return a
constraints on breakpoint placement.  This method is not needed by
most targets.

The FR-V target (see frv-tdep.c') requires this method.  The FR-V
is a VLIW architecture in which a number of RISC-like instructions
are grouped (packed) together into an aggregate instruction or
instruction bundle.  When the processor executes one of these
bundles, the component instructions are executed in parallel.

In the course of optimization, the compiler may group instructions
from distinct source statements into the same bundle.  The line
number information associated with one of the latter statements
will likely refer to some instruction other than the first one in
the bundle.  So, if the user attempts to place a breakpoint on one
of these latter statements, GDB must be careful to _not_ place the
break instruction on any instruction other than the first one in
the bundle.  (Remember though that the instructions within a
bundle execute in parallel, so the _first_ instruction is the
instruction at the lowest address and has nothing to do with
execution order.)

breakpoint's address by scanning backwards for the beginning of
the bundle, returning the address of the bundle.

Since the adjustment of a breakpoint may significantly alter a
user's expectation, GDB prints a warning when an adjusted
breakpoint is initially set and each time that that breakpoint is
hit.

int gdbarch_call_dummy_location (GDBARCH)'
See the file inferior.h'.

This method has been replaced by gdbarch_push_dummy_code' (*note
gdbarch_push_dummy_code::).

int gdbarch_cannot_fetch_register (GDBARCH, REGUM)'
This function should return nonzero if REGNO cannot be fetched
from an inferior process.

int gdbarch_cannot_store_register (GDBARCH, REGNUM)'
This function should return nonzero if REGNO should not be written
to the target.  This is often the case for program counters,
status words, and other special registers.  This function returns
0 as default so that GDB will assume that all registers may be
written.

int gdbarch_convert_register_p (GDBARCH, REGNUM, struct type *TYPE)'
Return non-zero if register REGNUM represents data values of type
TYPE in a non-standard form.  *Note Using Different Register and
Memory Data Representations: Target Architecture Definition.

int gdbarch_fp0_regnum (GDBARCH)'
This function returns the number of the first floating point
register, if the machine has such registers.  Otherwise, it
returns -1.

This function shall return the amount by which to decrement the PC
after the program encounters a breakpoint.  This is often the
number of bytes in BREAKPOINT', though not always.  For most
targets this value will be 0.

If defined, this should evaluate to 1 if ADDR is in a shared
library in which breakpoints cannot be set and so should be
disabled.

int gdbarch_dwarf2_reg_to_regnum (GDBARCH, DWARF2_REGNR)'
Convert DWARF2 register number DWARF2_REGNR into GDB regnum.  If
not defined, no conversion will be performed.

int gdbarch_ecoff_reg_to_regnum (GDBARCH, ECOFF_REGNR)'
Convert ECOFF register number  ECOFF_REGNR into GDB regnum.  If
not defined, no conversion will be performed.

GCC_COMPILED_FLAG_SYMBOL'
GCC2_COMPILED_FLAG_SYMBOL'
If defined, these are the names of the symbols that GDB will look
for to detect that GCC compiled the file.  The default symbols are
gcc_compiled.' and gcc2_compiled.', respectively.  (Currently
only defined for the Delta 68.)

gdbarch_get_longjmp_target'
This function determines the target PC address that longjmp' will
jump to, assuming that we have just stopped at a longjmp'
breakpoint.  It takes a CORE_ADDR *' as argument, and stores the
target PC value through this pointer.  It examines the current
state of the machine as needed, typically by using a
manually-determined offset into the jmp_buf'.  (While we might
like to get the offset from the target's jmpbuf.h', that header
file cannot be assumed to be available when building a
cross-debugger.)

DEPRECATED_IBM6000_TARGET'
Shows that we are configured for an IBM RS/6000 system.  This
conditional should be eliminated (FIXME) and replaced by
feature-specific macros.  It was introduced in haste and we are
repenting at leisure.

I386_USE_GENERIC_WATCHPOINTS'
An x86-based target can define this to use the generic x86
watchpoint support; see *note I386_USE_GENERIC_WATCHPOINTS:
Algorithms.

gdbarch_in_function_epilogue_p (GDBARCH, ADDR)'
Returns non-zero if the given ADDR is in the epilogue of a
function.  The epilogue of a function is defined as the part of a
function where the stack frame of the function already has been
destroyed up to the final return from function call' instruction.

int gdbarch_in_solib_return_trampoline (GDBARCH, PC, NAME)'
Define this function to return nonzero if the program is stopped
in the trampoline that returns from a shared library.

target_so_ops.in_dynsym_resolve_code (PC)'
Define this to return nonzero if the program is stopped in the

SKIP_SOLIB_RESOLVER (PC)'
Define this to evaluate to the (nonzero) address at which execution
should continue to get past the dynamic linker's symbol resolution
function.  A zero value indicates that it is not important or
necessary to set a breakpoint to get through the dynamic linker
and that single stepping will suffice.

Define this when the architecture needs to handle non-pointer to
according to the current architectures conventions.

_Pragmatics: When the user copies a well defined expression from
their source code and passes it, as a parameter, to GDB's print'
command, they should get the same value as would have been
computed by the target program.  Any deviation from this rule can
cause major confusion and annoyance, and needs to be justified
carefully.  In other words, GDB doesn't really have the freedom to
do these conversions in clever and useful ways.  It has, however,
been pointed out that users aren't complaining about how GDB casts
integers to pointers; they are complaining that they can't take an
an architecture method like gdbarch_integer_to_address' certainly
makes it possible for GDB to "get it right" in all circumstances._

*Note Pointers Are Not Always Addresses: Target Architecture
Definition.

Assume that BUF holds a pointer of type TYPE, in the appropriate
format for the current architecture.  Return the byte address the
pointer refers to.  *Note Pointers Are Not Always Addresses:
Target Architecture Definition.

void gdbarch_register_to_value(GDBARCH, FRAME, REGNUM, TYPE, FUR)'
Convert the raw contents of register REGNUM into a value of type
TYPE.  *Note Using Different Register and Memory Data
Representations: Target Architecture Definition.

REGISTER_CONVERT_TO_VIRTUAL(REG, TYPE, FROM, TO)'
Convert the value of register REG from its raw form to its virtual
form.  *Note Raw and Virtual Register Representations: Target
Architecture Definition.

REGISTER_CONVERT_TO_RAW(TYPE, REG, FROM, TO)'
Convert the value of register REG from its virtual form to its raw
form.  *Note Raw and Virtual Register Representations: Target
Architecture Definition.

const struct regset *regset_from_core_section (struct gdbarch * GDBARCH, const char * SECT_NAME, size_t SECT_SIZE)'
Return the appropriate register set for a core file section with
name SECT_NAME and size SECT_SIZE.

SOFTWARE_SINGLE_STEP_P()'
Define this as 1 if the target does not have a hardware single-step
mechanism.  The macro SOFTWARE_SINGLE_STEP' must also be defined.

SOFTWARE_SINGLE_STEP(SIGNAL, INSERT_BREAKPOINTS_P)'
A function that inserts or removes (depending on
INSERT_BREAKPOINTS_P) breakpoints at each possible destinations of
the next instruction.  See sparc-tdep.c' and rs6000-tdep.c' for
examples.

Somebody clever observed that, the more actual addresses you have
in the debug information, the more time the linker has to spend
relocating them.  So whenever there's some other way the debugger
could find the address it needs, you should omit it from the debug

Calling set_gdbarch_sofun_address_maybe_missing' with a non-zero
argument SET indicates that a particular set of hacks of this sort
are in use, affecting N_SO' and N_FUN' entries in stabs-format
debugging information.  N_SO' stabs mark the beginning and ending
addresses of compilation units in the text segment.  N_FUN' stabs
mark the starts and ends of functions.

In this case, GDB assumes two things:

* N_FUN' stabs have an address of zero.  Instead of using those
starts by taking the function name from the stab, and then
looking that up in the minsyms (the linker/assembler symbol
table).  In other words, the stab has the name, and the
linker/assembler symbol table is the only place that carries

* N_SO' stabs have an address of zero, too.  You just look at
the N_FUN' stabs that appear before and after the N_SO'
stab, and guess the starting and ending addresses of the
compilation unit from them.

Define this function to return nonzero if a function argument of
type TYPE is passed by reference instead of value.

CORE_ADDR gdbarch_push_dummy_call (GDBARCH, FUNCTION, REGCACHE, BP_ADDR, NARGS, ARGS, SP, STRUCT_RETURN, STRUCT_ADDR)'
Define this to push the dummy frame's call to the inferior
function onto the stack.  In addition to pushing NARGS, the code
should push STRUCT_ADDR (when STRUCT_RETURN is non-zero), and the

FUNCTION is a pointer to a struct value'; on architectures that
use function descriptors, this contains the function descriptor
value.

Returns the updated top-of-stack pointer.

CORE_ADDR gdbarch_push_dummy_code (GDBARCH, SP, FUNADDR, USING_GCC, ARGS, NARGS, VALUE_TYPE, REAL_PC, BP_ADDR, REGCACHE)'
Given a stack based call dummy, push the instruction sequence
(including space for a breakpoint) to which the called function
should return.

should be inserted, REAL_PC to the resume address when starting
the call sequence, and return the updated inner-most stack address.

By default, the stack is grown sufficient to hold a frame-aligned
reserved for that breakpoint, and REAL_PC set to FUNADDR.

This method replaces gdbarch_call_dummy_location (GDBARCH)'.

int gdbarch_sdb_reg_to_regnum (GDBARCH, SDB_REGNR)'
Use this function to convert sdb register SDB_REGNR into GDB
regnum.  If not defined, no conversion will be done.

enum return_value_convention gdbarch_return_value (struct gdbarch *GDBARCH, struct type *VALTYPE, struct regcache *REGCACHE, void *READBUF, const void *WRITEBUF)'
Given a function with a return-value of type RETTYPE, return which
return-value convention that function would use.

GDB currently recognizes two function return-value conventions:
RETURN_VALUE_REGISTER_CONVENTION' where the return value is found
in registers; and RETURN_VALUE_STRUCT_CONVENTION' where the return
value is found in memory and the address of that memory location is
passed in as the function's first parameter.

If the register convention is being used, and WRITEBUF is
non-NULL', also copy the return-value in WRITEBUF into REGCACHE.

If the register convention is being used, and READBUF is
non-NULL', also copy the return value from REGCACHE into READBUF
(REGCACHE contains a copy of the registers from the just returned
function).

_Maintainer note: This method replaces separate predicate, extract,
store methods.  By having only one method, the logic needed to
determine the return-value convention need only be implemented in
one place.  If GDB were written in an OO language, this method
would instead return an object that knew how to perform the
register return-value extract and store._

_Maintainer note: This method does not take a GCC_P parameter, and
such a parameter should not be added.  If an architecture that
requires per-compiler or per-function information be identified,
then the replacement of RETTYPE with struct value' FUNCTION
should be pursued._

_Maintainer note: The REGCACHE parameter limits this methods to
the inner most frame.  While replacing REGCACHE with a struct
frame_info' FRAME parameter would remove that limitation there has
yet to be a demonstrated need for such a change._

void gdbarch_skip_permanent_breakpoint (GDBARCH, REGCACHE)'
Advance the inferior's PC past a permanent breakpoint.  GDB
normally steps over a breakpoint by removing it, stepping one
instruction, and re-inserting the breakpoint.  However, permanent
breakpoints are hardwired into the inferior, and can't be removed,
so this strategy doesn't work.  Calling
so that execution will resume just after the breakpoint.  This
function does the right thing even when the breakpoint is in the
delay slot of a branch or jump.

CORE_ADDR gdbarch_skip_trampoline_code (GDBARCH, FRAME, PC)'
If the target machine has trampoline code that sits between
callers and the functions being called, then define this function
to return a new PC that is at the start of the real function.

int gdbarch_deprecated_fp_regnum (GDBARCH)'
If the frame pointer is in a register, use this function to return
the number of that register.

int gdbarch_stab_reg_to_regnum (GDBARCH, STAB_REGNR)'
Use this function to convert stab register STAB_REGNR into GDB
regnum.  If not defined, no conversion will be done.

defined in current sources.)

TARGET_CHAR_BIT'
Number of bits in a char; defaults to 8.

int gdbarch_char_signed (GDBARCH)'
Non-zero if char' is normally signed on this architecture; zero if
it should be unsigned.

The ISO C standard requires the compiler to treat char' as
equivalent to either signed char' or unsigned char'; any
character in the standard execution set is supposed to be positive.
Most compilers treat char' as signed, but char' is unsigned on
the IBM S/390, RS6000, and PowerPC targets.

int gdbarch_double_bit (GDBARCH)'
Number of bits in a double float; defaults to
8 * TARGET_CHAR_BIT'.

int gdbarch_float_bit (GDBARCH)'
Number of bits in a float; defaults to 4 * TARGET_CHAR_BIT'.

int gdbarch_int_bit (GDBARCH)'
Number of bits in an integer; defaults to 4 * TARGET_CHAR_BIT'.

int gdbarch_long_bit (GDBARCH)'
Number of bits in a long integer; defaults to
4 * TARGET_CHAR_BIT'.

int gdbarch_long_double_bit (GDBARCH)'
Number of bits in a long double float; defaults to
2 * gdbarch_double_bit (GDBARCH)'.

int gdbarch_long_long_bit (GDBARCH)'
Number of bits in a long long integer; defaults to
2 * gdbarch_long_bit (GDBARCH)'.

int gdbarch_ptr_bit (GDBARCH)'
Number of bits in a pointer; defaults to
gdbarch_int_bit (GDBARCH)'.

int gdbarch_short_bit (GDBARCH)'
Number of bits in a short integer; defaults to
2 * TARGET_CHAR_BIT'.

void gdbarch_virtual_frame_pointer (GDBARCH, PC, FRAME_REGNUM, FRAME_OFFSET)'
Returns a (REGISTER, OFFSET)' pair representing the virtual frame
pointer in use at the code address PC.  If virtual frame pointers
are not used, a default definition simply returns
gdbarch_deprecated_fp_regnum' (or gdbarch_sp_regnum', if no
frame pointer is defined), with an offset of zero.

TARGET_HAS_HARDWARE_WATCHPOINTS'
If non-zero, the target has support for hardware-assisted
watchpoints.  *Note watchpoints: Algorithms, for more details and
other related macros.

int gdbarch_print_insn (GDBARCH, VMA, INFO)'
This is the function used by GDB to print an assembly instruction.
It prints the instruction at address VMA in debugged memory and
returns the length of the instruction, in bytes.  This usually
points to a function in the opcodes' library (*note Opcodes:
Support Libraries.).  INFO is a structure (of type
disassemble_info') defined in the header file
include/dis-asm.h', and used to pass information to the
instruction decoding routine.

frame_id gdbarch_dummy_id (GDBARCH, FRAME)'
Given FRAME return a struct frame_id' that uniquely identifies an
inferior function call's dummy frame.  The value returned must
match the dummy frame stack value previously saved by
call_function_by_hand'.

void gdbarch_value_to_register (GDBARCH, FRAME, TYPE, BUF)'
Convert a value of type TYPE into the raw contents of a register.
*Note Using Different Register and Memory Data Representations:
Target Architecture Definition.

Motorola M68K target conditionals.

BPT_VECTOR'
Define this to be the 4-bit location of the breakpoint trap
vector.  If not defined, it will default to 0xf'.

REMOTE_BPT_VECTOR'
Defaults to 1'.

File: gdbint.info,  Node: Adding a New Target,  Prev: Defining Other Architecture Features,  Up: Target Architecture Definition

=========================

The following files add a target to GDB:

gdb/TTT-tdep.c'
Contains any miscellaneous code required for this target machine.
On some machines it doesn't exist at all.

gdb/ARCH-tdep.c'
gdb/ARCH-tdep.h'
This is required to describe the basic layout of the target
machine's processor chip (registers, stack, etc.).  It can be
shared among many targets that use the same processor architecture.

(Target header files such as gdb/config/ARCH/tm-TTT.h',
gdb/config/ARCH/tm-ARCH.h', and config/tm-OS.h' are no longer used.)

A GDB description for a new architecture, arch is created by
defining a global function _initialize_ARCH_tdep', by convention in
the source file ARCH-tdep.c'.  For example, in the case of the
OpenRISC 1000, this function is called _initialize_or1k_tdep' and is
found in the file or1k-tdep.c'.

The object file resulting from compiling this source file, which will
contain the implementation of the _initialize_ARCH_tdep' function is
specified in the GDB configure.tgt' file, which includes a large case
statement pattern matching against the --target' option of the
configure' script.

_Note:_ If the architecture requires multiple source files, the
corresponding binaries should be included in configure.tgt'.
However if there are header files, the dependencies on these will
not be picked up from the entries in configure.tgt'. The
Makefile.in' file will need extending to show these dependencies.

A new struct gdbarch, defining the new architecture, is created
within the _initialize_ARCH_tdep' function by calling
gdbarch_register':

void gdbarch_register (enum bfd_architecture    architecture,
gdbarch_init_ftype      *init_func,
gdbarch_dump_tdep_ftype *tdep_dump_func);

This function has been described fully in an earlier section.  *Note
How an Architecture is Represented: How an Architecture is Represented.

The new struct gdbarch' should contain implementations of the
necessary functions (described in the previous sections) to describe
the basic layout of the target machine's processor chip (registers,
stack, etc.).  It can be shared among many targets that use the same
processor architecture.

File: gdbint.info,  Node: Target Descriptions,  Next: Target Vector Definition,  Prev: Target Architecture Definition,  Up: Top

12 Target Descriptions
**********************

The target architecture definition (*note Target Architecture
Definition::) contains GDB's hard-coded knowledge about an
architecture.  For some platforms, it is handy to have more flexible
knowledge about a specific instance of the architecture--for instance,
a processor or development board.  "Target descriptions" provide a
mechanism for the user to tell GDB more about what their target
supports, or for the target to tell GDB directly.

For details on writing, automatically supplying, and manually
selecting target descriptions, see *note Target Descriptions:
(gdb)Target Descriptions.  This section will cover some related topics

* Target Descriptions Implementation::
* Adding Target Described Register Support::

File: gdbint.info,  Node: Target Descriptions Implementation,  Next: Adding Target Described Register Support,  Up: Target Descriptions

12.1 Target Descriptions Implementation
=======================================

Before GDB connects to a new target, or runs a new program on an
existing target, it discards any existing target description and
reverts to a default gdbarch.  Then, after connecting, it looks for a
new target description by calling target_find_description'.

A description may come from a user specified file (XML), the remote
qXfer:features:read' packet (also XML), or from any custom
to_read_description' routine in the target vector.  For instance, the
remote target supports guessing whether a MIPS target is 32-bit or
64-bit based on the size of the g' packet.

If any target description is found, GDB creates a new gdbarch
incorporating the description by calling gdbarch_update_p'.  Any
<architecture>' element is handled first, to determine which
architecture's gdbarch initialization routine is called to create the
new architecture.  Then the initialization routine is called, and has a
chance to adjust the constructed architecture based on the contents of
the target description.  For instance, it can recognize any properties
Described Register Support::.

File: gdbint.info,  Node: Adding Target Described Register Support,  Prev: Target Descriptions Implementation,  Up: Target Descriptions

12.2 Adding Target Described Register Support
=============================================

instance of the target.  But it takes a little work in the architecture
specific routines to support this.

A target description must either have no registers or a complete
set--this avoids complexity in trying to merge standard registers with
the target defined registers.  It is the architecture's responsibility
to validate that a description with registers has everything it needs.
To keep architecture code simple, the same mechanism is used to assign
fixed internal register numbers to standard registers.

If tdesc_has_registers' returns 1, the description contains
registers.  The architecture's gdbarch_init' routine should:

* Call tdesc_data_alloc' to allocate storage, early, before
searching for a matching gdbarch or allocating a new one.

* Use tdesc_find_feature' to locate standard features by name.

* Use tdesc_numbered_register' and tdesc_numbered_register_choices'
to locate the expected registers in the standard features.

* Return NULL' if a required feature is missing, or if any standard
feature is missing expected registers.  This will produce a
warning that the description was incomplete.

* Free the allocated data before returning, unless
tdesc_use_registers' is called.

* Call set_gdbarch_num_regs' as usual, with a number higher than any
fixed number passed to tdesc_numbered_register'.

* Call tdesc_use_registers' after creating a new gdbarch, before
returning it.

After tdesc_use_registers' has been called, the architecture's
register_name', register_type', and register_reggroup_p' routines
will not be called; that information will be taken from the target
description.  num_regs' may be increased to account for any additional
registers in the description.

Pseudo-registers require some extra care:

* Using tdesc_numbered_register' allows the architecture to give
constant register numbers to standard architectural registers, e.g.
as an enum' in ARCH-tdep.h'.  But because pseudo-registers are
always numbered above num_regs', which may be increased by the
description, constant numbers can not be used for pseudos.  They
must be numbered relative to num_regs' instead.

* The description will not describe pseudo-registers, so the
architecture must call set_tdesc_pseudo_register_name',
set_tdesc_pseudo_register_type', and
set_tdesc_pseudo_register_reggroup_p' to supply routines
describing pseudo registers.  These routines will be passed
internal register numbers, so the same routines used for the
gdbarch equivalents are usually suitable.

File: gdbint.info,  Node: Target Vector Definition,  Next: Native Debugging,  Prev: Target Descriptions,  Up: Top

13 Target Vector Definition
***************************

The target vector defines the interface between GDB's abstract handling
of target systems, and the nitty-gritty code that actually exercises
control over a process or a serial port.  GDB includes some 30-40
different target vectors; however, each configuration of GDB includes
only a few of them.

* Managing Execution State::
* Existing Targets::

File: gdbint.info,  Node: Managing Execution State,  Next: Existing Targets,  Up: Target Vector Definition

13.1 Managing Execution State
=============================

A target vector can be completely inactive (not pushed on the target
stack), active but not running (pushed, but not connected to a fully
manifested inferior), or completely active (pushed, with an accessible
inferior).  Most targets are only completely inactive or completely
active, but some support persistent connections to a target even when
the target has exited or not yet started.

For example, connecting to the simulator using target sim' does not
create a running program.  Neither registers nor memory are accessible
until run'.  Similarly, after kill', the program can not continue
executing.  But in both cases GDB remains connected to the simulator,
and target-specific commands are directed to the simulator.

A target which only supports complete activation should push itself
onto the stack in its to_open' routine (by calling push_target'), and
unpush itself from the stack in its to_mourn_inferior' routine (by
calling unpush_target').

A target which supports both partial and complete activation should
still call push_target' in to_open', but not call unpush_target' in
to_mourn_inferior'.  Instead, it should call either
target_mark_running' or target_mark_exited' in its to_open',
depending on whether the target is fully active after connection.  It
should also call target_mark_running' any time the inferior becomes
fully active (e.g. in to_create_inferior' and to_attach'), and
target_mark_exited' when the inferior becomes inactive (in
to_mourn_inferior').  The target should also make sure to call
target_mourn_inferior' from its to_kill', to return the target to
inactive state.

File: gdbint.info,  Node: Existing Targets,  Prev: Managing Execution State,  Up: Target Vector Definition

13.2 Existing Targets
=====================

13.2.1 File Targets
-------------------

Both executables and core files have target vectors.

13.2.2 Standard Protocol and Remote Stubs
-----------------------------------------

GDB's file remote.c' talks a serial protocol to code that runs in the
target system.  GDB provides several sample "stubs" that can be
integrated into target programs or operating systems for this purpose;
they are named CPU-stub.c'.  Many operating systems, embedded targets,
emulators, and simulators already have a GDB stub built into them, and
maintenance of the remote protocol must be careful to preserve
compatibility.

The GDB user's manual describes how to put such a stub into your
target code.  What follows is a discussion of integrating the SPARC
stub into a complicated operating system (rather than a simple
program), by Stu Grossman, the author of this stub.

The trap handling code in the stub assumes the following upon entry
to trap_low':

1. %l1 and %l2 contain pc and npc respectively at the time of the
trap;

2. traps are disabled;

3. you are in the correct trap window.

As long as your trap handler can guarantee those conditions, then
there is no reason why you shouldn't be able to "share" traps with the
stub.  The stub has no requirement that it be jumped to directly from
the hardware trap vector.  That is why it calls exceptionHandler()',
which is provided by the external environment.  For instance, this could
set up the hardware traps to actually execute code which calls the stub
first, and then transfers to its own trap handler.

For the most point, there probably won't be much of an issue with
"sharing" traps, as the traps we use are usually not used by the kernel,
and often indicate unrecoverable error conditions.  Anyway, this is all
controlled by a table, and is trivial to modify.  The most important
trap for us is for ta 1'.  Without that, we can't single step or do
breakpoints.  Everything else is unnecessary for the proper operation
of the debugger/stub.

From reading the stub, it's probably not obvious how breakpoints
work.  They are simply done by deposit/examine operations from GDB.

13.2.3 ROM Monitor Interface
----------------------------

13.2.4 Custom Protocols
-----------------------

13.2.5 Transport Layer
----------------------

13.2.6 Builtin Simulator
------------------------

File: gdbint.info,  Node: Native Debugging,  Next: Support Libraries,  Prev: Target Vector Definition,  Up: Top

14 Native Debugging
*******************

Several files control GDB's configuration for native support:

gdb/config/ARCH/XYZ.mh'
Specifies Makefile fragments needed by a _native_ configuration on
machine XYZ.  In particular, this lists the required
native-dependent object files, by defining NATDEPFILES=...'.
Also specifies the header file which describes native support on
XYZ, by defining NAT_FILE= nm-XYZ.h'.  You can also define
NAT_CFLAGS', NAT_ADD_FILES', NAT_CLIBS', NAT_CDEPS',
NAT_GENERATED_FILES', etc.; see Makefile.in'.

_Maintainer's note: The .mh' suffix is because this file
originally contained Makefile' fragments for hosting GDB on
machine XYZ.  While the file is no longer used for this purpose,
the .mh' suffix remains.  Perhaps someone will eventually rename
these fragments so that they have a .mn' suffix._

gdb/config/ARCH/nm-XYZ.h'
(nm.h' is a link to this file, created by configure').  Contains
C macro definitions describing the native system environment, such
as child process control and core file support.

gdb/XYZ-nat.c'
Contains any miscellaneous C code required for this native support
of this machine.  On some machines it doesn't exist at all.

There are some "generic" versions of routines that can be used by
various systems.  These can be customized in various ways by macros
defined in your nm-XYZ.h' file.  If these routines work for the XYZ
host, you can just include the generic file's name (with .o', not
.c') in NATDEPFILES'.

Otherwise, if your machine needs custom support routines, you will
need to write routines that perform the same functions as the generic
file.  Put them into XYZ-nat.c', and put XYZ-nat.o' into
NATDEPFILES'.

inftarg.c'
This contains the _target_ops vector_ that supports Unix child
processes on systems which use ptrace and wait to control the
child.

procfs.c'
This contains the _target_ops vector_ that supports Unix child
processes on systems which use /proc to control the child.

fork-child.c'
This does the low-level grunge that uses Unix system calls to do a
"fork and exec" to start up a child process.

infptrace.c'
This is the low level interface to inferior processes for systems
using the Unix ptrace' call in a vanilla way.

14.1 ptrace
===========

14.2 /proc
==========

14.3 win32
==========

14.4 shared libraries
=====================

14.5 Native Conditionals
========================

When GDB is configured and compiled, various macros are defined or left
undefined, to control compilation when the host and target systems are
the same.  These macros should be defined (or left undefined) in
nm-SYSTEM.h'.

I386_USE_GENERIC_WATCHPOINTS'
An x86-based machine can define this to use the generic x86
watchpoint support; see *note I386_USE_GENERIC_WATCHPOINTS:
Algorithms.

Define this to expand into an expression that will cause the
symbols in FILENAME to be added to GDB's symbol table.  If
READSYMS is zero symbols are not read but any necessary low level
processing for FILENAME is still done.

SOLIB_CREATE_INFERIOR_HOOK'
Define this to expand into any shared-library-relocation code that
you want to be run just after the child process has been forked.

START_INFERIOR_TRAPS_EXPECTED'
When starting an inferior, GDB normally expects to trap twice;
once when the shell execs, and once when the program itself execs.
If the actual number of traps is something other than 2, then
define this macro to expand into the number expected.

File: gdbint.info,  Node: Support Libraries,  Next: Coding,  Prev: Native Debugging,  Up: Top

15 Support Libraries
********************

15.1 BFD
========

BFD provides support for GDB in several ways:

_identifying executable and core files_
BFD will identify a variety of file types, including a.out, coff,
and several variants thereof, as well as several kinds of core
files.

BFD parses the file headers to determine the names, virtual
addresses, sizes, and file locations of all the various named
sections in files (such as the text section or the data section).
GDB simply calls BFD to read or write section X at byte offset Y
for length Z.

_specialized core file support_
BFD provides routines to determine the failing command name stored
in a core file, the signal with which the program failed, and
whether a core file matches (i.e. could be a core dump of) a
particular executable file.

_locating the symbol information_
GDB uses an internal interface of BFD to determine where to find
the symbol information in an executable file or symbol-file.  GDB
itself handles the reading of symbols, since BFD does not
"understand" debug symbols, but GDB uses BFD's cached information
to find the symbols, string table, etc.

15.2 opcodes
============

The opcodes library provides GDB's disassembler.  (It's a separate
library because it's also used in binutils, for objdump').

=============

The readline' library provides a set of functions for use by
applications that allow users to edit command lines as they are typed
in.

15.4 libiberty
==============

The libiberty' library provides a set of functions and features that
integrate and improve on functionality found in modern operating
systems.  Broadly speaking, such features can be divided into three
groups: supplemental functions (functions that may be missing in some
environments and operating systems), replacement functions (providing a
uniform and easier to use interface for commonly used standard
functions), and extensions (which provide additional functionality
beyond standard functions).

GDB uses various features provided by the libiberty' library, for
instance the C++ demangler, the IEEE floating format support functions,
the input options parser getopt', the obstack' extension, and other
functions.

15.4.1 obstacks' in GDB
------------------------

The obstack mechanism provides a convenient way to allocate and free
chunks of memory.  Each obstack is a pool of memory that is managed
like a stack.  Objects (of any nature, size and alignment) are
allocated and freed in a LIFO fashion on an obstack (see libiberty''s
documentation for a more detailed explanation of obstacks').

The most noticeable use of the obstacks' in GDB is in object files.
There is an obstack associated with each internal representation of an
object file.  Lots of things get allocated on these obstacks':
dictionary entries, blocks, blockvectors, symbols, minimal symbols,
types, vectors of fundamental types, class fields of types, object
files section lists, object files section offset lists, line tables,
symbol tables, partial symbol tables, string tables, symbol table
private data, macros tables, debug information sections and entries,
import and export lists (som), unwind information (hppa), dwarf2
location expressions data.  Plus various strings such as directory
names strings, debug format strings, names of types.

An essential and convenient property of all data on obstacks' is
that memory for it gets allocated (with obstack_alloc') at various
times during a debugging session, but it is released all at once using
the obstack_free' function.  The obstack_free' function takes a
pointer to where in the stack it must start the deletion from (much
like the cleanup chains have a pointer to where to start the cleanups).
Because of the stack like structure of the obstacks', this allows to
free only a top portion of the obstack.  There are a few instances in
GDB where such thing happens.  Calls to obstack_free' are done after
some local data is allocated to the obstack.  Only the local data is
deleted from the obstack.  Of course this assumes that nothing between
the obstack_alloc' and the obstack_free' allocates anything else on
the same obstack.  For this reason it is best and safest to use
temporary obstacks'.

Releasing the whole obstack is also not safe per se.  It is safe only
under the condition that we know the obstacks' memory is no longer
needed.  In GDB we get rid of the obstacks' only when we get rid of
the whole objfile(s), for instance upon reading a new symbol file.

15.5 gnu-regex
==============

Regex conditionals.

C_ALLOCA'

NFAILURES'

RE_NREGS'

SIGN_EXTEND_CHAR'

SWITCH_ENUM_BUG'

SYNTAX_TABLE'

Sword'

sparc'

15.6 Array Containers
=====================

Often it is necessary to manipulate a dynamic array of a set of
objects.  C forces some bookkeeping on this, which can get cumbersome
and repetitive.  The vec.h' file contains macros for defining and
using a typesafe vector type.  The functions defined will be inlined
when compiling, and so the abstraction cost should be zero.  Domain
checks are added to detect programming errors.

An example use would be an array of symbols or section information.
The array can be grown as symbols are read in (or preallocated), and
the accessor macros provided keep care of all the necessary
bookkeeping.  Because the arrays are type safe, there is no danger of
accidentally mixing up the contents.  Think of these as C++ templates,
but implemented in C.

Because of the different behavior of structure objects, scalar
objects and of pointers, there are three flavors of vector, one for
each of these variants.  Both the structure object and pointer variants
pass pointers to objects around -- in the former case the pointers are
stored into the vector and in the latter case the pointers are
dereferenced and the objects copied into the vector.  The scalar object
variant is suitable for int'-like objects, and the vector elements are
returned by value.

There are both index' and iterate' accessors.  The iterator
returns a boolean iteration condition and updates the iteration
variable passed by reference.  Because the iterator will be inlined,
the address-of can be optimized away.

The vectors are implemented using the trailing array idiom, thus they
are not resizeable without changing the address of the vector object
itself.  This means you cannot have variables or fields of vector type
-- always use a pointer to a vector.  The one exception is the final
field of a structure, which could be a vector type.  You will have to
use the embedded_size' & embedded_init' calls to create such objects,
and they will probably not be resizeable (so don't use the "safe"
allocation variants).  The trailing array idiom is used (rather than a
pointer to an array of data), because, if we allow NULL' to also
represent an empty vector, empty vectors occupy minimal space in the
structure containing them.

Each operation that increases the number of active elements is
available in "quick" and "safe" variants.  The former presumes that
there is sufficient allocated space for the operation to succeed (it
dies if there is not).  The latter will reallocate the vector, if
needed.  Reallocation causes an exponential increase in vector size.
If you know you will be adding N elements, it would be more efficient
to use the reserve operation before adding the elements with the
"quick" operation.  This will ensure there are at least as many
elements as you ask for, it will exponentially increase if there are
too few spare slots.  If you want reserve a specific number of slots,
but do not want the exponential increase (for instance, you know this
is the last allocation), use a negative number for reservation.  You
can also create a vector of a specific size from the get go.

You should prefer the push and pop operations, as they append and
remove from the end of the vector.  If you need to remove several items
in one go, use the truncate operation.  The insert and remove
operations allow you to change elements in the middle of the vector.
There are two remove operations, one which preserves the element
ordering ordered_remove', and one which does not unordered_remove'.
The latter function copies the end element into the removed slot,
rather than invoke a memmove operation.  The lower_bound' function
will determine where to place an item in the array using insert that
will maintain sorted order.

If you need to directly manipulate a vector, then the address'
accessor will return the address of the start of the vector.  Also the
space' predicate will tell you whether there is spare capacity in the
vector.  You will not normally need to use these two functions.

Vector types are defined using a DEF_VEC_{O,P,I}(TYPENAME)' macro.
Variables of vector type are declared using a VEC(TYPENAME)' macro.
The characters O', P' and I' indicate whether TYPENAME is an object
(O'), pointer (P') or integral (I') type.  Be careful to pick the
correct one, as you'll get an awkward and inefficient API if you use
the wrong one.  There is a check, which results in a compile-time
warning, for the P' and I' versions, but there is no check for the
O' versions, as that is not possible in plain C.

An example of their use would be,

DEF_VEC_P(tree);   // non-managed tree vector.

struct my_struct {
VEC(tree) *v;      // A (pointer to) a vector of tree pointers.
};

struct my_struct *s;

if (VEC_length(tree, s->v)) { we have some contents }
VEC_safe_push(tree, s->v, decl); // append some decl onto the end
for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++)
{ do something with elt }

The vec.h' file provides details on how to invoke the various
accessors provided.  They are enumerated here:

VEC_length'
Return the number of items in the array,

VEC_empty'
Return true if the array has no elements.

VEC_last'
VEC_index'
Return the last or arbitrary item in the array.

VEC_iterate'
Access an array element and indicate whether the array has been
traversed.

VEC_alloc'
VEC_free'
Create and destroy an array.

VEC_embedded_size'
VEC_embedded_init'
Helpers for embedding an array as the final element of another
struct.

VEC_copy'
Duplicate an array.

VEC_space'
Return the amount of free space in an array.

VEC_reserve'
Ensure a certain amount of free space.

VEC_quick_push'
VEC_safe_push'
Append to an array, either assuming the space is available, or
making sure that it is.

VEC_pop'
Remove the last item from an array.

VEC_truncate'
Remove several items from the end of an array.

VEC_safe_grow'
Add several items to the end of an array.

VEC_replace'
Overwrite an item in the array.

VEC_quick_insert'
VEC_safe_insert'
Insert an item into the middle of the array.  Either the space must
already exist, or the space is created.

VEC_ordered_remove'
VEC_unordered_remove'
Remove an item from the array, preserving order or not.

VEC_block_remove'
Remove a set of items from the array.

Provide the address of the first element.

VEC_lower_bound'
Binary search the array.

15.7 include
============

File: gdbint.info,  Node: Coding,  Next: Porting GDB,  Prev: Support Libraries,  Up: Top

16 Coding
*********

This chapter covers topics that are lower-level than the major
algorithms of GDB.

16.1 Cleanups
=============

Cleanups are a structured way to deal with things that need to be done
later.

When your code does something (e.g., xmalloc' some memory, or
open' a file) that needs to be undone later (e.g., xfree' the memory
or close' the file), it can make a cleanup.  The cleanup will be done
at some future point: when the command is finished and control returns
to the top level; when an error occurs and the stack is unwound; or
when your code decides it's time to explicitly perform cleanups.
Alternatively you can elect to discard the cleanups you created.

Syntax:

struct cleanup *OLD_CHAIN;'
Declare a variable which will hold a cleanup chain handle.

OLD_CHAIN = make_cleanup (FUNCTION, ARG);'
Make a cleanup which will cause FUNCTION to be called with ARG (a
char *') later.  The result, OLD_CHAIN, is a handle that can
later be passed to do_cleanups' or discard_cleanups'.  Unless
you are going to call do_cleanups' or discard_cleanups', you can
ignore the result from make_cleanup'.

do_cleanups (OLD_CHAIN);'
Do all cleanups added to the chain since the corresponding
make_cleanup' call was made.

Same as do_cleanups' except that it just removes the cleanups from
the chain and does not call the specified functions.

Cleanups are implemented as a chain.  The handle returned by
make_cleanups' includes the cleanup passed to the call and any later
cleanups appended to the chain (but not yet discarded or performed).
E.g.:

make_cleanup (a, 0);
{
struct cleanup *old = make_cleanup (b, 0);
make_cleanup (c, 0)
...
do_cleanups (old);
}

will call c()' and b()' but will not call a()'.  The cleanup that
calls a()' will remain in the cleanup chain, and will be done later

creates.  Failing to do this leads to non-deterministic behavior since
This need leads to two common cleanup styles.

The first style is try/finally.  Before it exits, your code-block
calls do_cleanups' with the old cleanup chain and thus ensures that
your code-block's cleanups are always performed.  For instance, the
following code-segment avoids a memory leak problem (even when error'
is called and a forced stack unwind occurs) by ensuring that the
xfree' will always be called:

struct cleanup *old = make_cleanup (null_cleanup, 0);
data = xmalloc (sizeof blah);
make_cleanup (xfree, data);
... blah blah ...
do_cleanups (old);

The second style is try/except.  Before it exits, your code-block
calls discard_cleanups' with the old cleanup chain and thus ensures
that any created cleanups are not performed.  For instance, the
following code segment, ensures that the file will be closed but only
if there is an error:

FILE *file = fopen ("afile", "r");
struct cleanup *old = make_cleanup (close_file, file);
... blah blah ...
return file;

Some functions, e.g., fputs_filtered()' or error()', specify that
they "should not be called when cleanups are not in place".  This means
that any actions you need to reverse in the case of an error or
interruption must be on the cleanup chain before you call these
functions, since they might never return to your code (they longjmp'

16.2 Per-architecture module data
=================================

The multi-arch framework includes a mechanism for adding module
specific per-architecture data-pointers to the struct gdbarch'
architecture object.

A module registers one or more per-architecture data-pointers using:

-- Architecture Function: struct gdbarch_data *
gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *PRE_INIT)
PRE_INIT is used to, on-demand, allocate an initial value for a
per-architecture data-pointer using the architecture's obstack
(passed in as a parameter).  Since PRE_INIT can be called during
architecture creation, it is not parameterized with the
architecture.  and must not call modules that use per-architecture
data.

-- Architecture Function: struct gdbarch_data *
gdbarch_data_register_post_init (gdbarch_data_post_init_ftype
*POST_INIT)
POST_INIT is used to obtain an initial value for a
per-architecture data-pointer _after_.  Since POST_INIT is always
called after architecture creation, it both receives the fully
initialized architecture and is free to call modules that use
per-architecture data (care needs to be taken to ensure that those
other modules do not try to call back to this module as that will
create in cycles in the initialization call graph).

These functions return a struct gdbarch_data' that is used to
identify the per-architecture data-pointer added for that module.

The per-architecture data-pointer is accessed using the function:

-- Architecture Function: void * gdbarch_data (struct gdbarch
*GDBARCH, struct gdbarch_data *DATA_HANDLE)
Given the architecture ARCH and module data handle DATA_HANDLE
(returned by gdbarch_data_register_pre_init' or
gdbarch_data_register_post_init'), this function returns the
current value of the per-architecture data-pointer.  If the data
pointer is NULL', it is first initialized by calling the
corresponding PRE_INIT or POST_INIT method.

The examples below assume the following definitions:

struct nozel { int total; };
static struct gdbarch_data *nozel_handle;

per-architecture data, using the PRE_INIT method.  The module's
per-architecture data is then initialized during architecture creation.

In the below, the module's per-architecture _nozel_ is added.  An
architecture can specify its nozel by calling set_gdbarch_nozel' from
gdbarch_init'.

static void *
nozel_pre_init (struct obstack *obstack)
{
struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
return data;
}

extern void
set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
{
struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
data->total = nozel;
}

A module can on-demand create architecture dependent data structures
using post_init'.

In the below, the nozel's total is computed on-demand by
nozel_post_init' using information obtained from the architecture.

static void *
nozel_post_init (struct gdbarch *gdbarch)
{
struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
nozel->total = gdbarch... (gdbarch);
return data;
}

extern int
nozel_total (struct gdbarch *gdbarch)
{
struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
return data->total;
}

16.3 Wrapping Output Lines
==========================

Output that goes through printf_filtered' or fputs_filtered' or
fputs_demangled' needs only to have calls to wrap_here' added in
places that would be good breaking points.  The utility routines will
take care of actually wrapping if the line width is exceeded.

The argument to wrap_here' is an indentation string which is
printed _only_ if the line breaks there.  This argument is saved away
and used later.  It must remain valid until the next call to
wrap_here' or until a newline has been printed through the
*_filtered' functions.  Don't pass in a local variable and then return!

It is usually best to call wrap_here' after printing a comma or
space.  If you call it before printing a space, make sure that your
indentation properly accounts for the leading space that will print if
the line wraps there.

Any function or set of functions that produce filtered output must
finish by printing a newline, to flush the wrap buffer, before switching
to unfiltered (printf') output.  Symbol reading routines that print
warnings are a good example.

16.4 GDB Coding Standards
=========================

GDB follows the GNU coding standards, as described in
etc/standards.texi'.  This file is also available for anonymous FTP
from GNU archive sites.  GDB takes a strict interpretation of the
standard; in general, when the GNU standard recommends a practice but
does not require it, GDB requires it.

GDB follows an additional set of coding standards specific to GDB,
as described in the following sections.

16.4.1 ISO C
------------

GDB assumes an ISO/IEC 9899:1990 (a.k.a. ISO C90) compliant compiler.

GDB does not assume an ISO C or POSIX compliant C library.

16.4.2 Memory Management
------------------------

GDB does not use the functions malloc', realloc', calloc', free'
and asprintf'.

GDB uses the functions xmalloc', xrealloc' and xcalloc' when
allocating memory.  Unlike malloc' et.al.  these functions do not
return when the memory pool is empty.  Instead, they unwind the stack
using cleanups.  These functions return NULL' when requested to
allocate a chunk of memory of size zero.

_Pragmatics: By using these functions, the need to check every
memory allocation is removed.  These functions provide portable
behavior._

GDB does not use the function free'.

GDB uses the function xfree' to return memory to the memory pool.
Consistent with ISO-C, this function ignores a request to free a NULL'
pointer.

_Pragmatics: On some systems free' fails when passed a NULL'
pointer._

GDB can use the non-portable function alloca' for the allocation of
small temporary values (such as strings).

_Pragmatics: This function is very non-portable.  Some systems
restrict the memory being allocated to no more than a few kilobytes._

GDB uses the string function xstrdup' and the print function
xstrprintf'.

_Pragmatics: asprintf' and strdup' can fail.  Print functions such
as sprintf' are very prone to buffer overflow errors._

16.4.3 Compiler Warnings
------------------------

With few exceptions, developers should avoid the configuration option
--disable-werror' when building GDB.  The exceptions are listed in the
file gdb/MAINTAINERS'.  The default, when building with GCC, is
--enable-werror'.

This option causes GDB (when built using GCC) to be compiled with a
carefully selected list of compiler warning flags.  Any warnings from
those flags are treated as errors.

The current list of warning flags includes:

-Wall'
Recommended GCC warnings.

-Wdeclaration-after-statement'
GCC 3.x (and later) and C99 allow declarations mixed with code,
but GCC 2.x and C89 do not.

-Wpointer-arith'

-Wformat-nonliteral'
Non-literal format strings, with a few exceptions, are bugs - they
might contain unintended user-supplied format specifiers.  Since
GDB uses the format printf' attribute on all printf' like
functions this checks not just printf' calls but also calls to
functions such as fprintf_unfiltered'.

-Wno-pointer-sign'
In version 4.0, GCC began warning about pointer argument passing or
assignment even when the source and destination differed only in
signedness.  However, most GDB code doesn't distinguish carefully
between char' and unsigned char'.  In early 2006 the GDB
developers decided correcting these warnings wasn't worth the time
it would take.

-Wno-unused-parameter'
Due to the way that GDB is implemented many functions have unused
parameters.  Consequently this warning is avoided.  The macro
ATTRIBUTE_UNUSED' is not used as it leads to false negatives --
it is not an error to have ATTRIBUTE_UNUSED' on a parameter that
is being used.

-Wno-unused'
-Wno-switch'
-Wno-char-subscripts'
These are warnings which might be useful for GDB, but are
currently too noisy to enable with -Werror'.

16.4.4 Formatting
-----------------

The standard GNU recommendations for formatting must be followed
strictly.

A function declaration should not have its name in column zero.  A
function definition should have its name in column zero.

/* Declaration */
static void foo (void);
/* Definition */
void
foo (void)
{
}

_Pragmatics: This simplifies scripting.  Function definitions can be
found using ^function-name'._

There must be a space between a function or macro name and the
opening parenthesis of its argument list (except for macro definitions,
as required by C).  There must not be a space after an open
paren/bracket or before a close paren/bracket.

use more than one blank line to separate blocks, and avoid adding
whitespace after the end of a program line (as of 1/99, some 600 lines
had whitespace after the semicolon).  Excess whitespace causes
difficulties for diff' and patch' utilities.

Pointers are declared using the traditional K&R C style:

void *foo;

and not:

void * foo;
void* foo;

---------------

The standard GNU requirements on comments must be followed strictly.

Block comments must appear in the following form, with no /*'- or
*/'-only lines, and no leading *':

/* Wait for control to return from inferior to debugger.  If inferior
gets a signal, we may decide to start it up again instead of
returning.  That is why there is a loop in this function.  When
this function actually returns it means the inferior should be left
stopped and GDB should read more commands.  */

(Note that this format is encouraged by Emacs; tabbing for a
multi-line comment works correctly, and M-q' fills the block
consistently.)

Put a blank line between the block comments preceding function or
variable definitions, and the definition itself.

In general, put function-body comments on lines by themselves, rather
than trying to fit them into the 20 characters left at the end of a
line, since either the comment or the code will inevitably get longer
than will fit, and then somebody will have to move it anyhow.

16.4.6 C Usage
--------------

Code must not depend on the sizes of C data types, the format of the
host's floating point numbers, the alignment of anything, or the order
of evaluation of expressions.

Use functions freely.  There are only a handful of compute-bound
areas in GDB that might be affected by the overhead of a function call,
mainly in symbol reading.  Most of GDB's performance is limited by the
target interface (whether serial line or system call).

However, use functions with moderation.  A thousand one-line
functions are just as hard to understand as a single thousand-line
function.

_Macros are bad, M'kay._ (But if you have to use a macro, make sure
that the macro arguments are protected with parentheses.)

Declarations like struct foo *' should be used in preference to
declarations like typedef struct foo { ... } *foo_ptr'.

16.4.7 Function Prototypes
--------------------------

Prototypes must be used when both _declaring_ and _defining_ a
function.  Prototypes for GDB functions must include both the argument
type and name, with the name matching that used in the actual function
definition.

All external functions should have a declaration in a header file
that callers include, except for _initialize_*' functions, which must
be external so that init.c' construction works, but shouldn't be
visible to random source files.

Where a source file needs a forward declaration of a static function,
that declaration must appear in a block near the top of the source file.

16.4.8 Internal Error Recovery
------------------------------

During its execution, GDB can encounter two types of errors.  User
errors and internal errors.  User errors include not only a user
entering an incorrect command but also problems arising from corrupt
object files and system errors when interacting with the target.
Internal errors include situations where GDB has detected, at run time,
a corrupt or erroneous situation.

When reporting an internal error, GDB uses internal_error' and
gdb_assert'.

GDB must not call abort' or assert'.

_Pragmatics: There is no internal_warning' function.  Either the
code detected a user error, recovered from it and issued a warning' or
the code failed to correctly recover from the user error and issued an
internal_error'._

16.4.9 Command Names
--------------------

GDB U/I commands are written foo-bar', not foo_bar'.

16.4.10 File Names
------------------

Any file used when building the core of GDB must be in lower case.  Any
file used when building the core of GDB must be 8.3 unique.  These
requirements apply to both source and generated files.

_Pragmatics: The core of GDB must be buildable on many platforms
including DJGPP and MacOS/HFS.  Every time an unfriendly file is
introduced to the build process both Makefile.in' and configure.in'
need to be modified accordingly.  Compare the convoluted conversion
process needed to transform COPYING' into copying.c' with the
conversion needed to transform version.in' into version.c'._

Any file non 8.3 compliant file (that is not used when building the
core of GDB) must be added to gdb/config/djgpp/fnchange.lst'.

_Pragmatics: This is clearly a compromise._

When GDB has a local version of a system header file (ex string.h')
the file name based on the POSIX header prefixed with gdb_'
(gdb_string.h').  These headers should be relatively independent: they
should use only macros defined by configure', the compiler, or the
host; they should include only system headers; they should refer only
to system types.  They may be shared between multiple programs, e.g.
GDB and GDBSERVER.

For other files -' is used as the separator.

16.4.11 Include Files
---------------------

A .c' file should include defs.h' first.

A .c' file should directly include the .h' file of every
declaration and/or definition it directly refers to.  It cannot rely on
indirect inclusion.

A .h' file should directly include the .h' file of every
declaration and/or definition it directly refers to.  It cannot rely on
indirect inclusion.  Exception: The file defs.h' does not need to be
directly included.

An external declaration should only appear in one include file.

An external declaration should never appear in a .c' file.
Exception: a declaration for the _initialize' function that pacifies
-Wmissing-declaration'.

A typedef' definition should only appear in one include file.

An opaque struct' declaration can appear in multiple .h' files.
Where possible, a .h' file should use an opaque struct' declaration

All .h' files should be wrapped in:

#ifndef INCLUDE_FILE_NAME_H
#define INCLUDE_FILE_NAME_H
#endif

16.4.12 Clean Design and Portable Implementation
------------------------------------------------

In addition to getting the syntax right, there's the little question of
semantics.  Some things are done in certain ways in GDB because long
experience has shown that the more obvious ways caused various kinds of
trouble.

You can't assume the byte order of anything that comes from a target
(including VALUEs, object files, and instructions).  Such things must
be byte-swapped using SWAP_TARGET_AND_HOST' in GDB, or one of the swap
routines defined in bfd.h', such as bfd_get_32'.

You can't assume that you know what interface is being used to talk
to the target system.  All references to the target must go through the
current target_ops' vector.

You can't assume that the host and target machines are the same
machine (except in the "native" support modules).  In particular, you
can't assume that the target machine's header files will be available
on the host machine.  Target code must bring along its own header files
- written from scratch or explicitly donated by their owner, to avoid

Insertion of new #ifdef''s will be frowned upon.  It's much better
to write the code portably than to conditionalize it for various
systems.

New #ifdef''s which test for specific compilers or manufacturers or
operating systems are unacceptable.  All #ifdef''s should test for
features.  The information about which configurations contain which
features should be segregated into the configuration files.  Experience
has proven far too often that a feature unique to one particular system
often creeps into other systems; and that a conditional based on some
predefined macro for your current system will become worthless over
time, as new versions of your system come out that behave differently
with regard to this feature.

Adding code that handles specific architectures, operating systems,
target interfaces, or hosts, is not acceptable in generic code.

One particularly notorious area where system dependencies tend to
creep in is handling of file names.  The mainline GDB code assumes
Posix semantics of file names: absolute file names begin with a forward
slash /', slashes are used to separate leading directories,
case-sensitive file names.  These assumptions are not necessarily true
on non-Posix systems such as MS-Windows.  To avoid system-dependent
code where you need to take apart or construct a file name, use the
following portable macros:

HAVE_DOS_BASED_FILE_SYSTEM'
This preprocessing symbol is defined to a non-zero value on hosts
whose filesystems belong to the MS-DOS/MS-Windows family.  Use this
symbol to write conditional code which should only be compiled for
such hosts.

IS_DIR_SEPARATOR (C)'
Evaluates to a non-zero value if C is a directory separator
character.  On Unix and GNU/Linux systems, only a slash /' is
such a character, but on Windows, both /' and \' will pass.

IS_ABSOLUTE_PATH (FILE)'
Evaluates to a non-zero value if FILE is an absolute file name.
For Unix and GNU/Linux hosts, a name which begins with a slash /'
is absolute.  On DOS and Windows, d:/foo' and x:\bar' are also
absolute file names.

FILENAME_CMP (F1, F2)'
Calls a function which compares file names F1 and F2 as
appropriate for the underlying host filesystem.  For Posix systems,
this simply calls strcmp'; on case-insensitive filesystems it

DIRNAME_SEPARATOR'
Evaluates to a character which separates directories in
PATH'-style lists, typically held in environment variables.  This
character is :' on Unix, ;' on DOS and Windows.

SLASH_STRING'
This evaluates to a constant string you should use to produce an
absolute filename from leading directories and the file's basename.
SLASH_STRING' is "/"' on most systems, but might be "\\"' for
some Windows-based ports.

In addition to using these macros, be sure to use portable library
functions whenever possible.  For example, to extract a directory or a
basename part from a file name, use the dirname' and basename'
library functions (available in libiberty' for platforms which don't
provide them), instead of searching for a slash with strrchr'.

Another way to generalize GDB along a particular interface is with an
attribute struct.  For example, GDB has been generalized to handle
multiple kinds of remote interfaces--not by #ifdef's everywhere, but
by defining the target_ops' structure and having a current target (as
well as a stack of targets below it, for memory references).  Whenever
something needs to be done that depends on which remote interface we are
using, a flag in the current target_ops structure is tested (e.g.,
target_has_stack'), or a function is called through a pointer in the
current target_ops structure.  In this way, when a new remote interface
is added, only one module needs to be touched--the one that actually
implements the new remote interface.  Other examples of

Please avoid duplicating code.  For example, in GDB 3.x all the code
interfacing between ptrace' and the rest of GDB was duplicated in
*-dep.c', and so changing something was very painful.  In GDB 4.x,
these have all been consolidated into infptrace.c'.  infptrace.c' can
deal with variations between systems the same way any system-independent
file would (hooks, #if defined', etc.), and machines which are
radically different don't need to use infptrace.c' at all.

All debugging code must be controllable using the set debug MODULE'
command.  Do not use printf' to print trace messages.  Use
fprintf_unfiltered(gdb_stdlog, ...'.  Do not use #ifdef DEBUG'.

File: gdbint.info,  Node: Porting GDB,  Next: Versions and Branches,  Prev: Coding,  Up: Top

17 Porting GDB
**************

Most of the work in making GDB compile on a new machine is in
specifying the configuration of the machine.  Porting a new
architecture to GDB can be broken into a number of steps.

* Ensure a BFD exists for executables of the target architecture in
the bfd' directory.  If one does not exist, create one by
modifying an existing similar one.

* Implement a disassembler for the target architecture in the
opcodes' directory.

* Define the target architecture in the gdb' directory (*note
the new target to configure.tgt' with the names of the files that
contain the code.  By convention the target architecture
definition for an architecture ARCH is placed in ARCH-tdep.c'.

Within ARCH-tdep.c' define the function _initialize_ARCH_tdep'
which calls gdbarch_register' to create the new struct gdbarch'
for the architecture.

* If a new remote target is needed, consider adding a new remote
target by defining a function _initialize_remote_ARCH'.  However
if at all possible use the GDB _Remote Serial Protocol_ for this
and implement the server side protocol independently with the
target.

* If desired implement a simulator in the sim' directory.  This
should create the library libsim.a' implementing the interface in
remote-sim.h' (found in the include' directory).

* Build and test.  If desired, lobby the GDB steering group to have
the new port included in the main distribution!

* Add a description of the new architecture to the main GDB user
guide (*note Configuration Specific Information:
(gdb)Configuration Specific Information.).

File: gdbint.info,  Node: Versions and Branches,  Next: Start of New Year Procedure,  Prev: Porting GDB,  Up: Top

18 Versions and Branches
************************

18.1 Versions
=============

GDB's version is determined by the file gdb/version.in' and takes one
of the following forms:

MAJOR.MINOR
MAJOR.MINOR.PATCHLEVEL
an official release (e.g., 6.2 or 6.2.1)

MAJOR.MINOR.PATCHLEVEL.YYYYMMDD
a snapshot taken at YYYY-MM-DD-gmt (e.g., 6.1.50.20020302,
6.1.90.20020304, or 6.1.0.20020308)

MAJOR.MINOR.PATCHLEVEL.YYYYMMDD-cvs
a CVS check out drawn on YYYY-MM-DD (e.g., 6.1.50.20020302-cvs,
6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)

MAJOR.MINOR.PATCHLEVEL.YYYYMMDD (VENDOR)
a vendor specific release of GDB, that while based on

GDB's mainline uses the MAJOR and MINOR version numbers from the
most recent release branch, with a PATCHLEVEL of 50.  At the time each
new release branch is created, the mainline's MAJOR and MINOR version
numbers are updated.

GDB's release branch is similar.  When the branch is cut, the
PATCHLEVEL is changed from 50 to 90.  As draft releases are drawn from
the branch, the PATCHLEVEL is incremented.  Once the first release
(MAJOR.MINOR) has been made, the PATCHLEVEL is set to 0 and updates
have an incremented PATCHLEVEL.

For snapshots, and CVS check outs, it is also possible to identify
the CVS origin:

MAJOR.MINOR.50.YYYYMMDD
drawn from the HEAD of mainline CVS (e.g., 6.1.50.20020302)

MAJOR.MINOR.90.YYYYMMDD
MAJOR.MINOR.91.YYYYMMDD ...
drawn from a release branch prior to the release (e.g.,
6.1.90.20020304)

MAJOR.MINOR.0.YYYYMMDD
MAJOR.MINOR.1.YYYYMMDD ...
drawn from a release branch after the release (e.g.,
6.2.0.20020308)

If the previous GDB version is 6.1 and the current version is 6.2,
then, substituting 6 for MAJOR and 1 or 2 for MINOR, here's an
illustration of a typical sequence:

|
6.1.50.20020302-cvs
|
+--------------------------.
|                    <gdb_6_2-branch>
|                          |
6.2.50.20020303-cvs        6.1.90 (draft #1)
|                          |
6.2.50.20020304-cvs        6.1.90.20020304-cvs
|                          |
6.2.50.20020305-cvs        6.1.91 (draft #2)
|                          |
6.2.50.20020306-cvs        6.1.91.20020306-cvs
|                          |
6.2.50.20020307-cvs        6.2 (release)
|                          |
6.2.50.20020308-cvs        6.2.0.20020308-cvs
|                          |
6.2.50.20020309-cvs        6.2.1 (update)
|                          |
6.2.50.20020310-cvs         <branch closed>
|
6.2.50.20020311-cvs
|
+--------------------------.
|                     <gdb_6_3-branch>
|                          |
6.3.50.20020312-cvs        6.2.90 (draft #1)
|                          |

18.2 Release Branches
=====================

GDB draws a release series (6.2, 6.2.1, ...) from a single release
branch, and identifies that branch using the CVS branch tags:

gdb_MAJOR_MINOR-YYYYMMDD-branchpoint
gdb_MAJOR_MINOR-branch
gdb_MAJOR_MINOR-YYYYMMDD-release

_Pragmatics: To help identify the date at which a branch or release
is made, both the branchpoint and release tags include the date that
they are cut (YYYYMMDD) in the tag.  The branch tag, denoting the head
of the branch, does not need this._

18.3 Vendor Branches
====================

To avoid version conflicts, vendors are expected to modify the file
gdb/version.in' to include a vendor unique alphabetic identifier (an
official GDB release never uses alphabetic characters in its version
identifier).  E.g., 6.2widgit2', or 6.2 (Widgit Inc Patch 2)'.

18.4 Experimental Branches
==========================

18.4.1 Guidelines
-----------------

GDB permits the creation of branches, cut from the CVS repository, for
experimental development.  Branches make it possible for developers to
share preliminary work, and maintainers to examine significant new
developments.

The following are a set of guidelines for creating such branches:

_a branch has an owner_
The owner can set further policy for a branch, but may not change
the ground rules.  In particular, they can set a policy for
commits (be it adding more reviewers or deciding who can commit).

_all commits are posted_
All changes committed to a branch shall also be posted to the GDB
patches mailing list <gdb-patchesATsourceware.org>.  While
commentary on such changes are encouraged, people should remember
that the changes only apply to a branch.

_all commits are covered by an assignment_
This ensures that all changes belong to the Free Software
Foundation, and avoids the possibility that the branch may become
contaminated.

_a branch is focused_
A focused branch has a single objective or goal, and does not
contain unnecessary or irrelevant changes.  Cleanups, where
identified, being be pushed into the mainline as soon as possible.

_a branch tracks mainline_
This keeps the level of divergence under control.  It also keeps
the pressure on developers to push cleanups and other stuff into
the mainline.

_a branch shall contain the entire GDB module_
The GDB module gdb' should be specified when creating a branch
(branches of individual files should be avoided).  *Note Tags::.

_a branch shall be branded using version.in'_
The file gdb/version.in' shall be modified so that it identifies
the branch OWNER and branch NAME, e.g.,
6.2.50.20030303_owner_name' or 6.2 (Owner Name)'.

18.4.2 Tags
-----------

To simplify the identification of GDB branches, the following branch
tagging convention is strongly recommended:

OWNER_NAME-YYYYMMDD-branchpoint'
OWNER_NAME-YYYYMMDD-branch'
The branch point and corresponding branch tag.  YYYYMMDD is the
date that the branch was created.  A branch is created using the
sequence:
cvs rtag OWNER_NAME-YYYYMMDD-branchpoint gdb
cvs rtag -b -r OWNER_NAME-YYYYMMDD-branchpoint \
OWNER_NAME-YYYYMMDD-branch gdb

OWNER_NAME-YYYYMMDD-mergepoint'
The tagged point, on the mainline, that was used when merging the
branch on YYYYMMDD.  To merge in all changes since the branch was
cut, use a command sequence like:
cvs rtag OWNER_NAME-YYYYMMDD-mergepoint gdb
cvs update \
-jOWNER_NAME-YYYYMMDD-branchpoint
-jOWNER_NAME-YYYYMMDD-mergepoint
Similar sequences can be used to just merge in changes since the
last merge.

For further information on CVS, see Concurrent Versions System
(http://www.gnu.org/software/cvs/).

File: gdbint.info,  Node: Start of New Year Procedure,  Next: Releasing GDB,  Prev: Versions and Branches,  Up: Top

19 Start of New Year Procedure
******************************

At the start of each new year, the following actions should be
performed:

* Rotate the ChangeLog file

The current ChangeLog' file should be renamed into
ChangeLog-YYYY' where YYYY is the year that has just passed.  A
new ChangeLog' file should be created, and its contents should
contain a reference to the previous ChangeLog.  The following
should also be preserved at the end of the new ChangeLog, in order
to provide the appropriate settings when editing this file with
Emacs:
Local Variables:
mode: change-log
left-margin: 8
fill-column: 74
version-control: never
coding: utf-8
End:

* Add an entry for the newly created ChangeLog file
(ChangeLog-YYYY') in gdb/config/djgpp/fnchange.lst'.

* Update the copyright year in the startup message

*   file top.c', function print_gdb_version'

*   file gdbserver/server.c', function gdbserver_version'

*   file gdbserver/gdbreplay.c', function gdbreplay_version'

* Run the copyright.sh' script to add the new year in the copyright
notices of most source files.  This script requires Emacs 22 or
later to be installed.

* The new year also needs to be added manually in all other files
*   *.s'

*   *.f'

*   *.f90'

*   *.igen'

*   *.ac'

*   *.texi'

*   *.texinfo'

*   *.tex'

*   *.defs'

*   *.1'

File: gdbint.info,  Node: Releasing GDB,  Next: Testsuite,  Prev: Start of New Year Procedure,  Up: Top

20 Releasing GDB
****************

20.1 Branch Commit Policy
=========================

The branch commit policy is pretty slack.  GDB releases 5.0, 5.1 and
5.2 all used the below:

* The gdb/MAINTAINERS' file still holds.

* Don't fix something on the branch unless/until it is also fixed in
the trunk.  If this isn't possible, mentioning it in the
gdb/PROBLEMS' file is better than committing a hack.

* When considering a patch for the branch, suggested criteria
include: Does it fix a build?  Does it fix the sequence break
main; run' when debugging a static binary?

* The further a change is from the core of GDB, the less likely the
change will worry anyone (e.g., target specific code).

* Only post a proposal to change the core of GDB after you've sent
individual bribes to all the people listed in the MAINTAINERS'
file ;-)

_Pragmatics: Provided updates are restricted to non-core
functionality there is little chance that a broken change will be fatal.
This means that changes such as adding a new architectures or (within
reason) support for a new host are considered acceptable._

20.2 Obsoleting code
====================

Before anything else, poke the other developers (and around the source
code) to see if there is anything that can be removed from GDB (an old
target, an unused file).

Obsolete code is identified by adding an OBSOLETE' prefix to every
line.  Doing this means that it is easy to identify something that has
been obsoleted when greping through the sources.

The process is done in stages -- this is mainly to ensure that the
wider GDB community has a reasonable opportunity to respond.  Remember,
everything on the Internet takes a week.

1. Post the proposal on the GDB mailing list <gdbATsourceware.org>
Creating a bug report to track the task's state, is also highly
recommended.

2. Wait a week or so.

3. Post the proposal on the GDB Announcement mailing list
<gdb-announceATsourceware.org>.

4. Wait a week or so.

5. Go through and edit all relevant files and lines so that they are
prefixed with the word OBSOLETE'.

6. Wait until the next GDB version, containing this obsolete code,
has been released.

7. Remove the obsolete code.

_Maintainer note: While removing old code is regrettable it is
hopefully better for GDB's long term development.  Firstly it helps the
developers by removing code that is either no longer relevant or simply
wrong.  Secondly since it removes any history associated with the file
(effectively clearing the slate) the developer has a much freer hand
when it comes to fixing broken files._

20.3 Before the Branch
======================

The most important objective at this stage is to find and fix simple
changes that become a pain to track once the branch is created.  For
instance, configuration problems that stop GDB from even building.  If
you can't get the problem fixed, document it in the gdb/PROBLEMS' file.

Prompt for gdb/NEWS'
---------------------

People always forget.  Send a post reminding them but also if you know
something interesting happened add it yourself.  The schedule' script
will mention this in its e-mail.

-------------------

Grab one of the nightly snapshots and then walk through the
gdb/README' looking for anything that can be improved.  The schedule'
script will mention this in its e-mail.

Refresh any imported files.
---------------------------

A number of files are taken from external repositories.  They include:

* texinfo/texinfo.tex'

* config.guess' et. al. (see the top-level MAINTAINERS' file)

* etc/standards.texi', etc/make-stds.texi'

Check the ARI
-------------

A.R.I. is an awk' script (Awk Regression Index ;-) that checks for a
number of errors and coding conventions.  The checks include things
like using malloc' instead of xmalloc' and file naming problems.
There shouldn't be any regressions.

20.3.1 Review the bug data base
-------------------------------

Close anything obviously fixed.

20.3.2 Check all cross targets build
------------------------------------

The targets are listed in gdb/MAINTAINERS'.

20.4 Cut the Branch
===================

Create the branch
-----------------

$u=5.1$  v=5.2
$V=echo$v | sed 's/\./_/g'
$D=date -u +%Y-%m-%d$  echo $u$V $D 5.1 5_2 2002-03-03$  echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \
-D $D-gmt gdb_$V-$D-branchpoint insight cvs -f -d :ext:sourceware.org:/cvs/src rtag -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight$  ^echo ^^
...
$echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \ -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight
cvs -f -d :ext:sourceware.org:/cvs/src rtag \
-b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight
$^echo ^^ ...$

* By using -D YYYY-MM-DD-gmt', the branch is forced to an exact
date/time.

* The trunk is first tagged so that the branch point can easily be
found.

* Insight, which includes GDB, is tagged at the same time.

* version.in' gets bumped to avoid version number conflicts.

* The reading of .cvsrc' is disabled using -f'.

Update version.in'
-------------------

$u=5.1$  v=5.2
$V=echo$v | sed 's/\./_/g'
$echo$u $v$V
5.1 5_2
$cd /tmp$  echo cvs -f -d :ext:sourceware.org:/cvs/src co \
-r gdb_$V-branch src/gdb/version.in cvs -f -d :ext:sourceware.org:/cvs/src co -r gdb_5_2-branch src/gdb/version.in$  ^echo ^^
U src/gdb/version.in
$cd src/gdb$  echo $u.90-0000-00-00-cvs > version.in$  cat version.in
5.1.90-0000-00-00-cvs
$cvs -f commit version.in * 0000-00-00' is used as a date to pump prime the version.in update mechanism. * .90' and the previous branch version are used as fairly arbitrary initial branch version number. Update the web and news pages ----------------------------- Something? Tweak cron to track the new branch ---------------------------------- The file gdbadmin/cron/crontab' contains gdbadmin's cron table. This file needs to be updated so that: * A daily timestamp is added to the file version.in'. * The new branch is included in the snapshot process. See the file gdbadmin/cron/README' for how to install the updated cron table. The file gdbadmin/ss/README' should also be reviewed to reflect any changes. That file is copied to both the branch/ and current/ snapshot directories. Update the NEWS and README files -------------------------------- The NEWS' file needs to be updated so that on the branch it refers to _changes in the current release_ while on the trunk it also refers to _changes since the current release_. The README' file needs to be updated so that it refers to the current release. Post the branch info -------------------- Send an announcement to the mailing lists: * GDB Announcement mailing list <gdb-announceATsourceware.org> * GDB Discussion mailing list <gdbATsourceware.org> and GDB Testers mailing list <gdb-testersATsourceware.org> _Pragmatics: The branch creation is sent to the announce list to ensure that people people not subscribed to the higher volume discussion list are alerted._ The announcement should include: * The branch tag. * How to check out the branch using CVS. * The date/number of weeks until the release. * The branch commit policy still holds. 20.5 Stabilize the branch ========================= Something goes here. 20.6 Create a Release ===================== The process of creating and then making available a release is broken down into a number of stages. The first part addresses the technical process of creating a releasable tar ball. The later stages address the process of releasing that tar ball. When making a release candidate just the first section is needed. 20.6.1 Create a release candidate --------------------------------- The objective at this stage is to create a set of tar balls that can be made available as a formal release (or as a less formal release candidate). Freeze the branch ................. Send out an e-mail notifying everyone that the branch is frozen to <gdb-patchesATsourceware.org>. Establish a few defaults. .........................$  b=gdb_5_2-branch
$v=5.2$  t=/sourceware/snapshot-tmp/gdbadmin-tmp
$echo$t/$b/$v
$mkdir -p$t/$b/$v
$cd$t/$b/$v
$pwd /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2$  which autoconf
$Notes: * Check the autoconf' version carefully. You want to be using the version documented in the toplevel README-maintainer-mode' file. It is very unlikely that the version of autoconf' installed in system directories (e.g., /usr/bin/autoconf') is correct. Check out the relevant modules: ...............................$  for m in gdb insight
do
( mkdir -p $m && cd$m && cvs -q -f -d /cvs/src co -P -r $b$m )
done
$Note: * The reading of .cvsrc' is disabled (-f') so that there isn't any confusion between what is written here and what your local cvs' really does. Update relevant files. ...................... gdb/NEWS' Major releases get their comments added as part of the mainline. Minor releases should probably mention any significant bugs that were fixed. Don't forget to include the ChangeLog' entry.$  emacs gdb/src/gdb/NEWS
...
c-x 4 a
...
c-x c-s c-x c-c
$cp gdb/src/gdb/NEWS insight/src/gdb/NEWS$  cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog

You'll need to update:

* The version.

* The update date.

* Who did it.

$emacs gdb/src/gdb/README ... c-x 4 a ... c-x c-s c-x c-c$  cp gdb/src/gdb/README insight/src/gdb/README
$cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog _Maintainer note: Hopefully the README' file was reviewed before the initial branch was cut so just a simple substitute is needed to get it updated._ _Maintainer note: Other projects generate README' and INSTALL' from the core documentation. This might be worth pursuing._ gdb/version.in'$  echo $v > gdb/src/gdb/version.in$  cat gdb/src/gdb/version.in
5.2
$emacs gdb/src/gdb/version.in ... c-x 4 a ... Bump to version ... c-x c-s c-x c-c$  cp gdb/src/gdb/version.in insight/src/gdb/version.in
$cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog Do the dirty work ................. This is identical to the process used to create the daily snapshot.$  for m in gdb insight
do
( cd $m/src && gmake -f src-release$m.tar )
done

If the top level source directory does not have src-release' (GDB
version 5.3.1 or earlier), try these commands instead:

$for m in gdb insight do ( cd$m/src && gmake -f Makefile.in $m.tar ) done Check the source files ...................... You're looking for files that have mysteriously disappeared. distclean' has the habit of deleting files it shouldn't. Watch out for the version.in' update cronjob'.$  ( cd gdb/src && cvs -f -q -n update )
M djunpack.bat
? gdb-5.1.91.tar
? proto-toplev
... lots of generated files ...
M gdb/ChangeLog
M gdb/NEWS
M gdb/version.in
... lots of generated files ...
$_Don't worry about the gdb.info-??' or gdb/p-exp.tab.c'. They were generated (and yes gdb.info-1' was also generated only something strange with CVS means that they didn't get suppressed). Fixing it would be nice though._ Create compressed versions of the release .........................................$  cp */src/*.tar .
$cp */src/*.bz2 .$  ls -F
gdb/ gdb-5.2.tar insight/ insight-5.2.tar
$for m in gdb insight do bzip2 -v -9 -c$m-$v.tar >$m-$v.tar.bz2 gzip -v -9 -c$m-$v.tar >$m-$v.tar.gz done$

Note:

* A pipe such as bunzip2 < xxx.bz2 | gzip -9 > xxx.gz' is not since,
in that mode, gzip' does not know the name of the file and, hence,
can not include it in the compressed file.  This is also why the
release process runs tar' and bzip2' as separate passes.

20.6.2 Sanity check the tar ball
--------------------------------

Pick a popular machine (Solaris/PPC?) and try the build on that.

$bunzip2 < gdb-5.2.tar.bz2 | tar xpf -$  cd gdb-5.2
$./configure$  make
...
$./gdb/gdb ./gdb/gdb GNU gdb 5.2 ... (gdb) b main Breakpoint 1 at 0x80732bc: file main.c, line 734. (gdb) run Starting program: /tmp/gdb-5.2/gdb/gdb Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL); (gdb) print args$1 = {argc = 136426532, argv = 0x821b7f0}
(gdb)

20.6.3 Make a release candidate available
-----------------------------------------

If this is a release candidate then the only remaining steps are:

1. Commit version.in' and ChangeLog'

2. Tweak version.in' (and ChangeLog' to read L.M.N-0000-00-00-cvs
so that the version update process can restart.

3. Make the release candidate available in
ftp://sourceware.org/pub/gdb/snapshots/branch'

4. Notify the relevant mailing lists ( <gdbATsourceware.org> and
<gdb-testersATsourceware.org> that the candidate is available.

20.6.4 Make a formal release available
--------------------------------------

(And you thought all that was required was to post an e-mail.)

Install on sware
................

Copy the new files to both the release and the old release directory:

$cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/$  cp *.bz2 *.gz ~ftp/pub/gdb/releases

Clean up the releases directory so that only the most recent releases
are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):

$cd ~ftp/pub/gdb/releases$  rm ...

Update the file README' and .message' in the releases directory:

$vi README ...$  rm -f .message
$ln README .message Update the web pages. ..................... htdocs/download/ANNOUNCEMENT' This file, which is posted as the official announcement, includes: * General announcement. * News. If making an M.N.1 release, retain the news from earlier M.N release. * Errata. htdocs/index.html' htdocs/news/index.html' htdocs/download/index.html' These files include: * Announcement of the most recent release. * News entry (remember to update both the top level and the news directory). These pages also need to be regenerate using index.sh'. download/onlinedocs/' You need to find the magic command that is used to generate the online docs from the .tar.bz2'. The best way is to look in the output from one of the nightly cron' jobs and then just edit accordingly. Something like:$  ~/ss/update-web-docs \
~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
$PWD/www \ /www/sourceware/htdocs/gdb/download/onlinedocs \ gdb download/ari/' Just like the online documentation. Something like:$  /bin/sh ~/ss/update-web-ari \
~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
$PWD/www \ /www/sourceware/htdocs/gdb/download/ari \ gdb Shadow the pages onto gnu ......................... Something goes here. Install the GDB tar ball on GNU ............................... At the time of writing, the GNU machine was gnudist.gnu.org' in ~ftp/gnu/gdb'. Make the ANNOUNCEMENT' ....................... Post the ANNOUNCEMENT' file you created above to: * GDB Announcement mailing list <gdb-announceATsourceware.org> * General GNU Announcement list <info-gnuATgnu.org> (but delay it a day or so to let things get out) * GDB Bug Report mailing list <bug-gdbATgnu.org> 20.6.5 Cleanup -------------- The release is out but you're still not finished. Commit outstanding changes .......................... In particular you'll need to commit any changes to: * gdb/ChangeLog' * gdb/version.in' * gdb/NEWS' * gdb/README' Tag the release ............... Something like:$  d=date -u +%Y-%m-%d
$echo$d
2002-01-24
$( cd insight/src/gdb && cvs -f -q update )$  ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release ) Insight is used since that contains more of the release than GDB. Mention the release on the trunk ................................ Just put something in the ChangeLog' so that the trunk also indicates when the release was made. Restart gdb/version.in' ........................ If gdb/version.in' does not contain an ISO date such as 2002-01-24' then the daily cronjob' won't update it. Having committed all the release changes it can be set to 5.2.0_0000-00-00-cvs' which will restart things (yes the _' is important - it affects the snapshot process). Don't forget the ChangeLog'. Merge into trunk ................ The files committed to the branch may also need changes merged into the trunk. Revise the release schedule ........................... Post a revised release schedule to GDB Discussion List <gdbATsourceware.org> with an updated announcement. The schedule can be generated by running:$  ~/ss/schedule date +%s schedule

The first parameter is approximate date/time in seconds (from the epoch)
of the most recent release.

Also update the schedule cronjob'.

20.7 Post release
=================

Remove any OBSOLETE' code.

File: gdbint.info,  Node: Testsuite,  Next: Hints,  Prev: Releasing GDB,  Up: Top

21 Testsuite
************

The testsuite is an important component of the GDB package.  While it
is always worthwhile to encourage user testing, in practice this is
rarely sufficient; users typically use only a small subset of the
available commands, and it has proven all too common for a change to
cause a significant regression that went unnoticed for some time.

The GDB testsuite uses the DejaGNU testing framework.  The tests
themselves are calls to various Tcl' procs; the framework runs all the
procs and summarizes the passes and fails.

21.1 Using the Testsuite
========================

To run the testsuite, simply go to the GDB object directory (or to the
testsuite's objdir) and type make check'.  This just sets up some
environment variables and invokes DejaGNU's runtest' script.  While
the testsuite is running, you'll get mentions of which test file is in
use, and a mention of any unexpected passes or fails.  When the
testsuite is finished, you'll get a summary that looks like this:

=== gdb Summary ===

# of expected passes            6016
# of unexpected failures        58
# of unexpected successes       5
# of expected failures          183
# of unresolved testcases       3
# of untested testcases         5

To run a specific test script, type:
make check RUNTESTFLAGS='TESTS'
where TESTS is a list of test script file names, separated by spaces.

If you use GNU make, you can use its -j' option to run the
testsuite in parallel.  This can greatly reduce the amount of time it
takes for the testsuite to run.  In this case, if you set
RUNTESTFLAGS' then, by default, the tests will be run serially even
under -j'.  You can override this and force a parallel run by setting
the make' variable FORCE_PARALLEL' to any non-empty value.  Note that
the parallel make check' assumes that you want to run the entire
testsuite, so it is not compatible with some dejagnu options, like
--directory'.

The ideal test run consists of expected passes only; however, reality
conspires to keep us from this ideal.  Unexpected failures indicate
real problems, whether in GDB or in the testsuite.  Expected failures
are still failures, but ones which have been decided are too hard to
deal with at the time; for instance, a test case might work everywhere
except on AIX, and there is no prospect of the AIX case being fixed in
the near future.  Expected failures should not be added lightly, since
you may be masking serious bugs in GDB.  Unexpected successes are
expected fails that are passing for some reason, while unresolved and
untested cases often indicate some minor catastrophe, such as the
compiler being unable to deal with a test program.

When making any significant change to GDB, you should run the
testsuite before and after the change, to confirm that there are no
regressions.  Note that truly complete testing would require that you
run the testsuite with all supported configurations and a variety of
compilers; however this is more than really necessary.  In many cases
testing with a single configuration is sufficient.  Other useful
options are to test one big-endian (Sparc) and one little-endian (x86)
host, a cross config with a builtin simulator (powerpc-eabi, mips-elf),
or a 64-bit host (Alpha).

for it as well; this way future GDB hackers can detect and fix their
changes that break the functionality you added.  Similarly, if you fix
a bug that was not previously reported as a test failure, please add a
test case for it.  Some cases are extremely difficult to test, such as
code that handles host OS failures or bugs in particular versions of
compilers, and it's OK not to try to write tests for all of those.

DejaGNU supports separate build, host, and target machines.  However,
some GDB test scripts do not work if the build machine and the host
machine are not the same.  In such an environment, these scripts will
give a result of "UNRESOLVED", like this:

UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.

21.2 Testsuite Parameters
=========================

Several variables exist to modify the behavior of the testsuite.

* TRANSCRIPT'

Sometimes it is convenient to get a transcript of the commands
which the testsuite sends to GDB.  For example, if GDB crashes
during testing, a transcript can be used to more easily
reconstruct the failure when running GDB under GDB.

You can instruct the GDB testsuite to write transcripts by setting
the DejaGNU variable TRANSCRIPT' (to any value) before invoking
runtest' or make check'.  The transcripts will be written into
DejaGNU's output directory.  One transcript will be made for each
invocation of GDB; they will be named transcript.N', where N is
an integer.  The first line of the transcript file will show how
GDB was invoked; each subsequent line is a command sent as input
to GDB.

make check RUNTESTFLAGS=TRANSCRIPT=y

Note that the transcript is not always complete.  In particular,
tests of completion can yield partial command lines.

* GDB'

Sometimes one wishes to test a different GDB than the one in the
build directory.  For example, one may wish to run the testsuite on
/usr/bin/gdb'.

make check RUNTESTFLAGS=GDB=/usr/bin/gdb

* GDBSERVER'

When testing a different GDB, it is often useful to also test a
different gdbserver.

make check RUNTESTFLAGS="GDB=/usr/bin/gdb GDBSERVER=/usr/bin/gdbserver"

* INTERNAL_GDBFLAGS'

When running the testsuite normally one doesn't want whatever is in
~/.gdbinit' to interfere with the tests, therefore the test
harness passes -nx' to GDB.  One also doesn't want any windowed
version of GDB, e.g., gdbtui', to run.  This is achieved via
INTERNAL_GDBFLAGS'.

set INTERNAL_GDBFLAGS "-nw -nx"

This is all well and good, except when testing an installed GDB
that has been configured with --with-system-gdbinit'.  Here one
does not want ~/.gdbinit' loaded but one may want the system
.gdbinit' file loaded.  This can be achieved by pointing $HOME' at a directory without a .gdbinit' and by overriding INTERNAL_GDBFLAGS' and removing -nx'. cd testsuite HOME=pwd runtest \ GDB=/usr/bin/gdb \ GDBSERVER=/usr/bin/gdbserver \ INTERNAL_GDBFLAGS=-nw There are two ways to run the testsuite and pass additional parameters to DejaGnu. The first is with make check' and specifying the makefile variable RUNTESTFLAGS'. make check RUNTESTFLAGS=TRANSCRIPT=y The second is to cd to the testsuite' directory and invoke the DejaGnu runtest' command directly. cd testsuite make site.exp runtest TRANSCRIPT=y 21.3 Testsuite Configuration ============================ It is possible to adjust the behavior of the testsuite by defining the global variables listed below, either in a site.exp' file, or in a board file. * gdb_test_timeout' Defining this variable changes the default timeout duration used during communication with GDB. More specifically, the global variable used during testing is timeout', but this variable gets reset to gdb_test_timeout' at the beginning of each testcase, making sure that any local change to timeout' in a testcase does not affect subsequent testcases. This global variable comes in handy when the debugger is slower than normal due to the testing environment, triggering unexpected TIMEOUT' test failures. Examples include when testing on a remote machine, or against a system where communications are slow. If not specifically defined, this variable gets automatically defined to the same value as timeout' during the testsuite initialization. The default value of the timeout is defined in the file gdb/testsuite/config/unix.exp' that is part of the GDB test suite(1). 21.4 Testsuite Organization =========================== The testsuite is entirely contained in gdb/testsuite'. While the testsuite includes some makefiles and configury, these are very minimal, and used for little besides cleaning up, since the tests themselves handle the compilation of the programs that GDB will run. The file testsuite/lib/gdb.exp' contains common utility procs useful for all GDB tests, while the directory testsuite/config' contains configuration-specific files, typically used for special-purpose definitions of procs like gdb_load' and gdb_start'. The tests themselves are to be found in testsuite/gdb.*' and subdirectories of those. The names of the test files must always end with .exp'. DejaGNU collects the test files by wildcarding in the test directories, so both subdirectories and individual files get chosen and run in alphabetical order. The following table lists the main types of subdirectories and what they are for. Since DejaGNU finds test files no matter where they are located, and since each test file sets up its own compilation and execution environment, this organization is simply for convenience and intelligibility. gdb.base' This is the base testsuite. The tests in it should apply to all configurations of GDB (but generic native-only tests may live here). The test programs should be in the subset of C that is valid K&R, ANSI/ISO, and C++ (#ifdef's are allowed if necessary, for instance for prototypes). gdb.LANG' Language-specific tests for any language LANG besides C. Examples are gdb.cp' and gdb.java'. gdb.PLATFORM' Non-portable tests. The tests are specific to a specific configuration (host or target), such as HP-UX or eCos. Example is gdb.hp', for HP-UX. gdb.COMPILER' Tests specific to a particular compiler. As of this writing (June 1999), there aren't currently any groups of tests in this category that couldn't just as sensibly be made platform-specific, but one could imagine a gdb.gcc', for tests of GDB's handling of GCC extensions. gdb.SUBSYSTEM' Tests that exercise a specific GDB subsystem in more depth. For instance, gdb.disasm' exercises various disassemblers, while gdb.stabs' tests pathways through the stabs symbol reader. 21.5 Writing Tests ================== In many areas, the GDB tests are already quite comprehensive; you should be able to copy existing tests to handle new cases. You should try to use gdb_test' whenever possible, since it includes cases to handle all the unexpected errors that might happen. However, it doesn't cost anything to add new test procedures; for instance, gdb.base/exprs.exp' defines a test_expr' that calls gdb_test' multiple times. Only use send_gdb' and gdb_expect' when absolutely necessary. Even if GDB has several valid responses to a command, you can use gdb_test_multiple'. Like gdb_test', gdb_test_multiple' recognizes internal errors and unexpected prompts. Do not write tests which expect a literal tab character from GDB. On some operating systems (e.g. OpenBSD) the TTY layer expands tabs to spaces, so by the time GDB's output reaches expect the tab is gone. The source language programs do _not_ need to be in a consistent style. Since GDB is used to debug programs written in many different styles, it's worth having a mix of styles in the testsuite; for instance, some GDB bugs involving the display of source lines would never manifest themselves if the programs used GNU coding style uniformly. ---------- Footnotes ---------- (1) If you are using a board file, it could override the test-suite default; search the board file for "timeout". File: gdbint.info, Node: Hints, Next: GDB Observers, Prev: Testsuite, Up: Top 22 Hints ******** Check the README' file, it often has useful information that does not appear anywhere else in the directory. * Menu: * Getting Started:: Getting started working on GDB * Debugging GDB:: Debugging GDB with itself File: gdbint.info, Node: Getting Started, Next: Debugging GDB, Up: Hints 22.1 Getting Started ==================== GDB is a large and complicated program, and if you first starting to work on it, it can be hard to know where to start. Fortunately, if you know how to go about it, there are ways to figure out what is going on. This manual, the GDB Internals manual, has information which applies generally to many parts of GDB. Information about particular functions or data structures are located in comments with those functions or data structures. If you run across a function or a global variable which does not have a comment correctly explaining what is does, this can be thought of as a bug in GDB; feel free to submit a bug report, with a suggested comment if you can figure out what the comment should say. If you find a comment which is actually wrong, be especially sure to report that. Comments explaining the function of macros defined in host, target, or native dependent files can be in several places. Sometimes they are repeated every place the macro is defined. Sometimes they are where the macro is used. Sometimes there is a header file which supplies a default definition of the macro, and the comment is there. This manual also documents all the available macros. Start with the header files. Once you have some idea of how GDB's internal symbol tables are stored (see symtab.h', gdbtypes.h'), you will find it much easier to understand the code which uses and creates those symbol tables. You may wish to process the information you are getting somehow, to enhance your understanding of it. Summarize it, translate it to another language, add some (perhaps trivial or non-useful) feature to GDB, use the code to predict what a test case would do and write the test case and verify your prediction, etc. If you are reading code and your eyes are starting to glaze over, this is a sign you need to use a more active approach. Once you have a part of GDB to start with, you can find more specifically the part you are looking for by stepping through each function with the next' command. Do not use step' or you will quickly get distracted; when the function you are stepping through calls another function try only to get a big-picture understanding (perhaps using the comment at the beginning of the function being called) of what it does. This way you can identify which of the functions being called by the function you are stepping through is the one which you are interested in. You may need to examine the data structures generated at each stage, with reference to the comments in the header files explaining what the data structures are supposed to look like. Of course, this same technique can be used if you are just reading the code, rather than actually stepping through it. The same general principle applies--when the code you are looking at calls something else, just try to understand generally what the code being called does, rather than worrying about all its details. A good place to start when tracking down some particular area is with a command which invokes that feature. Suppose you want to know how single-stepping works. As a GDB user, you know that the step' command invokes single-stepping. The command is invoked via command tables (see command.h'); by convention the function which actually performs the command is formed by taking the name of the command and adding _command', or in the case of an info' subcommand, _info'. For example, the step' command invokes the step_command' function and the info display' command invokes display_info'. When this convention is not followed, you might have to use grep' or M-x tags-search' in emacs, or run GDB on itself and set a breakpoint in execute_command'. If all of the above fail, it may be appropriate to ask for information on bug-gdb'. But _never_ post a generic question like "I was wondering if anyone could give me some tips about understanding GDB"--if we had some magic secret we would put it in this manual. Suggestions for improving the manual are always welcome, of course. File: gdbint.info, Node: Debugging GDB, Prev: Getting Started, Up: Hints 22.2 Debugging GDB with itself ============================== If GDB is limping on your machine, this is the preferred way to get it fully functional. Be warned that in some ancient Unix systems, like Ultrix 4.2, a program can't be running in one process while it is being debugged in another. Rather than typing the command ./gdb ./gdb', which works on Suns and such, you can copy gdb' to gdb2' and then type ./gdb ./gdb2'. When you run GDB in the GDB source directory, it will read gdb-gdb.gdb' file (plus possibly gdb-gdb.py' file) that sets up some simple things to make debugging gdb easier. The info' command, when executed without a subcommand in a GDB being debugged by gdb, will pop you back up to the top level gdb. See gdb-gdb.gdb' for details. If you use emacs, you will probably want to do a make TAGS' after you configure your distribution; this will put the machine dependent routines for your local machine where they will be accessed first by M-.' Also, make sure that you've either compiled GDB with your local cc, or have run fixincludes' if you are compiling with gcc. 22.3 Submitting Patches ======================= Thanks for thinking of offering your changes back to the community of GDB users. In general we like to get well designed enhancements. Thanks also for checking in advance about the best way to transfer the changes. The GDB maintainers will only install "cleanly designed" patches. This manual summarizes what we believe to be clean design for GDB. If the maintainers don't have time to put the patch in when it arrives, or if there is any question about a patch, it goes into a large queue with everyone else's patches and bug reports. The legal issue is that to incorporate substantial changes requires a copyright assignment from you and/or your employer, granting ownership of the changes to the Free Software Foundation. You can get the standard documents for doing this by sending mail to gnuATgnu.org' and asking for it. We recommend that people write in "All programs owned by the Free Software Foundation" as "NAME OF PROGRAM", so that changes in many programs (not just GDB, but GAS, Emacs, GCC, etc) can be contributed with only one piece of legalese pushed through the bureaucracy and filed with the FSF. We can't start merging changes until this paperwork is received by the FSF (their rules, which we follow since we maintain it for them). Technically, the easiest way to receive changes is to receive each feature as a small context diff or unidiff, suitable for patch'. Each message sent to me should include the changes to C code and header files for a single feature, plus ChangeLog' entries for each directory where files were modified, and diffs for any changes needed to the manuals (gdb/doc/gdb.texinfo' or gdb/doc/gdbint.texinfo'). If there are a lot of changes for a single feature, they can be split down into multiple messages. In this way, if we read and like the feature, we can add it to the sources with a single patch command, do some testing, and check it in. If you leave out the ChangeLog', we have to write one. If you leave out the doc, we have to puzzle out what needs documenting. Etc., etc. The reason to send each change in a separate message is that we will not install some of the changes. They'll be returned to you with questions or comments. If we're doing our job correctly, the message back to you will say what you have to fix in order to make the change acceptable. The reason to have separate messages for separate features is so that the acceptable changes can be installed while one or more changes are being reworked. If multiple features are sent in a single message, we tend to not put in the effort to sort out the acceptable changes from the unacceptable, so none of the features get installed until all are acceptable. If this sounds painful or authoritarian, well, it is. But we get a lot of bug reports and a lot of patches, and many of them don't get installed because we don't have the time to finish the job that the bug reporter or the contributor could have done. Patches that arrive complete, working, and well designed, tend to get installed on the day they arrive. The others go into a queue and get installed as time permits, which, since the maintainers have many demands to meet, may not be for quite some time. Please send patches directly to the GDB maintainers <gdb-patchesATsourceware.org>. 22.4 Build Script ================= The script gdb_buildall.sh' builds GDB with flag --enable-targets=all' set. This builds GDB with all supported targets activated. This helps testing GDB when doing changes that affect more than one architecture and is much faster than using gdb_mbuild.sh'. After building GDB the script checks which architectures are supported and then switches the current architecture to each of those to get information about the architecture. The test results are stored in log files in the directory the script was called from. File: gdbint.info, Node: GDB Observers, Next: GNU Free Documentation License, Prev: Hints, Up: Top Appendix A GDB Currently available observers ******************************************** A.1 Implementation rationale ============================ An "observer" is an entity which is interested in being notified when GDB reaches certain states, or certain events occur in GDB. The entity being observed is called the "subject". To receive notifications, the observer attaches a callback to the subject. One subject can have several observers. observer.c' implements an internal generic low-level event notification mechanism. This generic event notification mechanism is then re-used to implement the exported high-level notification management routines for all possible notifications. The current implementation of the generic observer provides support for contextual data. This contextual data is given to the subject when attaching the callback. In return, the subject will provide this contextual data back to the observer as a parameter of the callback. Note that the current support for the contextual data is only partial, as it lacks a mechanism that would deallocate this data when the callback is detached. This is not a problem so far, as this contextual data is only used internally to hold a function pointer. Later on, if a certain observer needs to provide support for user-level contextual data, then the generic notification mechanism will need to be enhanced to allow the observer to provide a routine to deallocate the data when attaching the callback. The observer implementation is also currently not reentrant. In particular, it is therefore not possible to call the attach or detach routines during a notification. A.2 Debugging ============= Observer notifications can be traced using the command set debug observer 1' (*note Optional messages about internal happenings: (gdb)Debugging Output.). A.3 normal_stop' Notifications =============================== GDB notifies all normal_stop' observers when the inferior execution has just stopped, the associated messages and annotations have been printed, and the control is about to be returned to the user. Note that the normal_stop' notification is not emitted when the execution stops due to a breakpoint, and this breakpoint has a condition that is not met. If the breakpoint has any associated commands list, the commands are executed after the notification is emitted. The following interfaces are available to manage observers: -- Function: extern struct observer *observer_attach_EVENT (observer_EVENT_ftype *F) Using the function F, create an observer that is notified when ever EVENT occurs, return the observer. -- Function: extern void observer_detach_EVENT (struct observer *OBSERVER); Remove OBSERVER from the list of observers to be notified when EVENT occurs. -- Function: extern void observer_notify_EVENT (void); Send a notification to all EVENT observers. The following observable events are defined: -- Function: void normal_stop (struct bpstats *BS, int PRINT_FRAME) The inferior has stopped for real. The BS argument describes the breakpoints were are stopped at, if any. Second argument PRINT_FRAME non-zero means display the location where the inferior has stopped. -- Function: void target_changed (struct target_ops *TARGET) The target's register contents have changed. -- Function: void executable_changed (void) The executable being debugged by GDB has changed: The user decided to debug a different program, or the program he was debugging has been modified since being loaded by the debugger (by being recompiled, for instance). -- Function: void inferior_created (struct target_ops *OBJFILE, int FROM_TTY) GDB has just connected to an inferior. For run', GDB calls this observer while the inferior is still stopped at the entry-point instruction. For attach' and core', GDB calls this observer immediately after connecting to the inferior, and before any information on the inferior has been printed. -- Function: void solib_loaded (struct so_list *SOLIB) The shared library specified by SOLIB has been loaded. Note that when GDB calls this observer, the library's symbols probably haven't been loaded yet. -- Function: void solib_unloaded (struct so_list *SOLIB) The shared library specified by SOLIB has been unloaded. Note that when GDB calls this observer, the library's symbols have not been unloaded yet, and thus are still available. -- Function: void new_objfile (struct objfile *OBJFILE) The symbol file specified by OBJFILE has been loaded. Called with OBJFILE equal to NULL' to indicate previously loaded symbol table data has now been invalidated. -- Function: void new_thread (struct thread_info *T) The thread specified by T has been created. -- Function: void thread_exit (struct thread_info *T, int SILENT) The thread specified by T has exited. The SILENT argument indicates that GDB is removing the thread from its tables without wanting to notify the user about it. -- Function: void thread_stop_requested (ptid_t PTID) An explicit stop request was issued to PTID. If PTID equals MINUS_ONE_PTID, the request applied to all threads. If ptid_is_pid(ptid)' returns true, the request applied to all threads of the process pointed at by PTID. Otherwise, the request applied to the single thread pointed at by PTID. -- Function: void target_resumed (ptid_t PTID) The target was resumed. The PTID parameter specifies which thread was resume, and may be RESUME_ALL if all threads are resumed. -- Function: void about_to_proceed (void) The target is about to be proceeded. -- Function: void breakpoint_created (int BPNUM) A new breakpoint has been created. The argument BPNUM is the number of the newly-created breakpoint. -- Function: void breakpoint_deleted (int BPNUM) A breakpoint has been destroyed. The argument BPNUM is the number of the newly-destroyed breakpoint. -- Function: void breakpoint_modified (int BPNUM) A breakpoint has been modified in some way. The argument BPNUM is the number of the modified breakpoint. -- Function: void tracepoint_created (int TPNUM) A new tracepoint has been created. The argument TPNUM is the number of the newly-created tracepoint. -- Function: void tracepoint_deleted (int TPNUM) A tracepoint has been destroyed. The argument TPNUM is the number of the newly-destroyed tracepoint. -- Function: void tracepoint_modified (int TPNUM) A tracepoint has been modified in some way. The argument TPNUM is the number of the modified tracepoint. -- Function: void architecture_changed (struct gdbarch *NEWARCH) The current architecture has changed. The argument NEWARCH is a pointer to the new architecture. -- Function: void thread_ptid_changed (ptid_t OLD_PTID, ptid_t NEW_PTID) The thread's ptid has changed. The OLD_PTID parameter specifies the old value, and NEW_PTID specifies the new value. -- Function: void inferior_added (struct inferior *INF) The inferior INF has been added to the list of inferiors. At this point, it might not be associated with any process. -- Function: void inferior_appeared (struct inferior *INF) The inferior identified by INF has been attached to a process. -- Function: void inferior_exit (struct inferior *INF) Either the inferior associated with INF has been detached from the process, or the process has exited. -- Function: void inferior_removed (struct inferior *INF) The inferior INF has been removed from the list of inferiors. This method is called immediately before freeing INF. -- Function: void memory_changed (CORE_ADDR ADDR, ssize_t LEN, const bfd_byte *DATA) Bytes from DATA to DATA + LEN have been written to the current inferior at ADDR. -- Function: void gdb_datadir_changed (void) Variable gdb_datadir has been set. The value may not necessarily change. -- Function: void test_notification (int SOMEARG) This observer is used for internal testing. Do not use. See testsuite/gdb.gdb/observer.exp. File: gdbint.info, Node: GNU Free Documentation License, Next: Index, Prev: GDB Observers, Up: Top Appendix B GNU Free Documentation License ***************************************** Version 1.3, 3 November 2008 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. http://fsf.org/' Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 0. PREAMBLE The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others. This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software. We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference. 1. APPLICABILITY AND DEFINITIONS This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law. A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language. A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) 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TERMINATION You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License. However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation. Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice. 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If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document. 11. RELICENSING "Massive Multiauthor Collaboration Site" (or "MMC Site") means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A "Massive Multiauthor Collaboration" (or "MMC") contained in the site means any set of copyrightable works thus published on the MMC site. "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization. "Incorporate" means to publish or republish a Document, in whole or in part, as part of another Document. An MMC is "eligible for relicensing" if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008. The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing. ADDENDUM: How to use this License for your documents ==================================================== To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: Copyright (C) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License''. If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software. File: gdbint.info, Node: Index, Prev: GNU Free Documentation License, Up: Top Index ***** [index] * Menu: *$fp:                                   Register Information Functions.
(line 126)
* $pc: Register Architecture Functions & Variables. (line 58) *$ps:                                   Register Architecture Functions & Variables.
(line  69)
* \$sp:                                   Register Architecture Functions & Variables.
(line  49)
* _initialize_ARCH_tdep <1>:             Adding a New Target. (line  22)
* _initialize_ARCH_tdep:                 How an Architecture is Represented.
(line  13)
* _initialize_language:                  Language Support.    (line  79)
* a.out format:                          Object File Formats. (line   9)
* about_to_proceed:                      GDB Observers.       (line 133)
* abstract interpretation of function prologues: Algorithms.  (line  48)
* add_cmd:                               User Interface.      (line  21)
* add_com:                               User Interface.      (line  21)
* add_setshow_cmd:                       User Interface.      (line  26)
* add_setshow_cmd_full:                  User Interface.      (line  26)
* adding a new host:                     Host Definition.     (line  13)
(line   6)
* adding source language:                Language Support.    (line  17)
(line   6)
(line   6)
* address_class_name_to_type_flags:      Defining Other Architecture Features.
(line  28)
* address_class_name_to_type_flags_p:    Defining Other Architecture Features.
(line  39)
* algorithms:                            Algorithms.          (line   6)
* align_down:                            Functions and Variable to Analyze Frames.
(line  46)
* align_up:                              Functions and Variable to Analyze Frames.
(line  46)
* allocate_symtab:                       Language Support.    (line  83)
* ARCH-tdep.c:                           How an Architecture is Represented.
(line  13)
* architecture representation:           How an Architecture is Represented.
(line   6)
* architecture_changed:                  GDB Observers.       (line 160)
* Array Containers:                      Support Libraries.   (line 131)
* assumptions about targets:             Coding.              (line 519)
* base of a frame:                       Frame Handling Terminology.
(line  28)
* BFD library:                           Support Libraries.   (line   9)
* bfd_arch_info:                         Looking Up an Existing Architecture.
(line  41)
* BIG_BREAKPOINT:                        Defining Other Architecture Features.
(line 100)
* BPT_VECTOR:                            Defining Other Architecture Features.
(line 536)
* BREAKPOINT:                            Defining Other Architecture Features.
(line  88)
(line 145)
* breakpoint_created:                    GDB Observers.       (line 136)
* breakpoint_deleted:                    GDB Observers.       (line 140)
* breakpoint_modified:                   GDB Observers.       (line 144)
* breakpoints:                           Algorithms.          (line 151)
* bug-gdb mailing list:                  Getting Started.     (line  72)
* build script:                          Debugging GDB.       (line  94)
* C data types:                          Coding.              (line 389)
* call frame information:                Algorithms.          (line  14)
* call stack frame:                      Stack Frames.        (line   6)
* calls to the inferior:                 Inferior Call Setup. (line   6)
* CC_HAS_LONG_LONG:                      Host Definition.     (line 105)
* CFI (call frame information):          Algorithms.          (line  14)
* checkpoints:                           Algorithms.          (line 600)
* cleanups:                              Coding.              (line  12)
* CLI:                                   User Interface.      (line  12)
(line   6)
* coding standards:                      Coding.              (line 215)
* COFF debugging info:                   Debugging File Formats.
(line  22)
* COFF format:                           Object File Formats. (line  24)
* command implementation:                Getting Started.     (line  60)
* command interpreter:                   User Interface.      (line  12)
* comment formatting:                    Coding.              (line 363)
* compiler warnings:                     Coding.              (line 271)
* Compressed DWARF 2 debugging info:     Debugging File Formats.
(line  42)
* computed values:                       Values.              (line  35)
* configure.tgt:                         How an Architecture is Represented.
(line  19)
(line   6)
* converting integers to addresses:      Defining Other Architecture Features.
(line 274)
* cooked register representation:        Raw and Cooked Registers.
(line   6)
* core files:                            Adding support for debugging core files.
(line   6)
* core_addr_greaterthan:                 Functions and Variable to Analyze Frames.
(line  30)
* core_addr_lessthan:                    Functions and Variable to Analyze Frames.
(line  30)
* CRLF_SOURCE_FILES:                     Host Definition.     (line  86)
* current_language:                      Language Support.    (line  75)
(line   6)
* data output:                           User Interface.      (line 254)
* data-pointer, per-architecture/per-module: Coding.          (line 100)
* debugging GDB:                         Debugging GDB.       (line   6)
* DEFAULT_PROMPT:                        Host Definition.     (line  93)
* deprecate_cmd:                         User Interface.      (line  32)
* DEPRECATED_IBM6000_TARGET:             Defining Other Architecture Features.
(line 242)
* deprecating commands:                  User Interface.      (line  32)
* design:                                Coding.              (line 514)
* DEV_TTY:                               Host Definition.     (line  96)
* DIRNAME_SEPARATOR:                     Coding.              (line 584)
* DISABLE_UNSETTABLE_BREAK:              Defining Other Architecture Features.
(line 211)
* do_cleanups:                           Coding.              (line  35)
* DOS text files:                        Host Definition.     (line  87)
* dummy frames:                          About Dummy Frames.  (line   6)
* DW_AT_byte_size:                       Address Classes.     (line   6)
* DWARF 2 debugging info:                Debugging File Formats.
(line  35)
* DWARF 3 debugging info:                Debugging File Formats.
(line  62)
* ECOFF debugging info:                  Debugging File Formats.
(line  28)
* ECOFF format:                          Object File Formats. (line  39)
* ELF format:                            Object File Formats. (line  72)
* evaluate_subexp:                       Language Support.    (line  58)
* executable_changed:                    GDB Observers.       (line  85)
* execution state:                       Managing Execution State.
(line   6)
* experimental branches:                 Versions and Branches.
(line 116)
* expression evaluation routines:        Language Support.    (line  58)
* expression parser:                     Language Support.    (line  21)
(line  52)
* field output functions:                User Interface.      (line 254)
* file names, portability:               Coding.              (line 552)
* FILENAME_CMP:                          Coding.              (line 578)
* find_pc_function:                      Partial Symbol Tables.
(line  40)
* find_pc_line:                          Partial Symbol Tables.
(line  40)
* find_sym_fns:                          Symbol Reading.      (line  13)
* finding a symbol:                      Partial Symbol Tables.
(line  37)
* fine-tuning gdbarch structure:         OS ABI Variant Handling.
(line  23)
* first floating point register:         Register Architecture Functions & Variables.
(line  78)
* FOPEN_RB:                              Host Definition.     (line 102)
* fp0_regnum:                            Register Architecture Functions & Variables.
(line  78)
* frame:                                 Stack Frames.        (line   6)
* frame ID:                              Stack Frames.        (line  41)
* frame pointer:                         Register Information Functions.
(line 126)
* frame, definition of base of a frame:  Frame Handling Terminology.
(line  28)
* frame, definition of innermost frame:  Frame Handling Terminology.
(line  24)
* frame, definition of NEXT frame:       Frame Handling Terminology.
(line  11)
* frame, definition of PREVIOUS frame:   Frame Handling Terminology.
(line  14)
* frame, definition of sentinel frame:   Frame Handling Terminology.
(line  52)
* frame, definition of sniffing:         Frame Handling Terminology.
(line  46)
* frame, definition of THIS frame:       Frame Handling Terminology.
(line   9)
* frame, definition of unwinding:        Frame Handling Terminology.
(line  41)
* frame_align:                           Functions and Variable to Analyze Frames.
(line  46)
* frame_base:                            Analyzing Stacks---Frame Sniffers.
(line  89)
* frame_base_append_sniffer:             Analyzing Stacks---Frame Sniffers.
(line  19)
* frame_base_set_default:                Analyzing Stacks---Frame Sniffers.
(line  22)
* frame_num_args:                        Functions to Access Frame Data.
(line  43)
* frame_red_zone_size:                   Functions and Variable to Analyze Frames.
(line  63)
* frame_register_unwind:                 Stack Frames.        (line  15)
* frame_unwind:                          Analyzing Stacks---Frame Sniffers.
(line  36)
* frame_unwind_append_sniffer:           Analyzing Stacks---Frame Sniffers.
(line  16)
* frame_unwind_append_unwinder:          Stack Frames.        (line  30)
* frame_unwind_got_address:              Stack Frames.        (line 105)
* frame_unwind_got_constant:             Stack Frames.        (line 101)
* frame_unwind_got_memory:               Stack Frames.        (line  98)
* frame_unwind_got_optimized:            Stack Frames.        (line  90)
* frame_unwind_got_register:             Stack Frames.        (line  93)
* frame_unwind_prepend_unwinder:         Stack Frames.        (line  30)
* free_all_types:                        Memory Management for Types.
(line  28)
* full symbol table:                     Partial Symbol Tables.
(line   8)
* function prologue:                     Prologue Caches.     (line   6)
* function prototypes:                   Coding.              (line 411)
* function usage:                        Coding.              (line 393)
* fundamental types:                     Types.               (line   9)
* GCC2_COMPILED_FLAG_SYMBOL:             Defining Other Architecture Features.
(line 225)
* GCC_COMPILED_FLAG_SYMBOL:              Defining Other Architecture Features.
(line 225)
* GDB source tree structure:             Overall Structure.   (line  83)
* gdb_byte:                              Register Caching.    (line  23)
* gdb_datadir_changed:                   GDB Observers.       (line 189)
* GDB_OSABI_AIX:                         OS ABI Variant Handling.
(line  90)
* GDB_OSABI_CYGWIN:                      OS ABI Variant Handling.
(line  87)
* GDB_OSABI_FREEBSD_AOUT:                OS ABI Variant Handling.
(line  51)
* GDB_OSABI_FREEBSD_ELF:                 OS ABI Variant Handling.
(line  54)
* GDB_OSABI_GO32:                        OS ABI Variant Handling.
(line  69)
* GDB_OSABI_HPUX_ELF:                    OS ABI Variant Handling.
(line  78)
* GDB_OSABI_HPUX_SOM:                    OS ABI Variant Handling.
(line  81)
* GDB_OSABI_HURD:                        OS ABI Variant Handling.
(line  39)
* GDB_OSABI_INTERIX:                     OS ABI Variant Handling.
(line  75)
* GDB_OSABI_IRIX:                        OS ABI Variant Handling.
(line  72)
* GDB_OSABI_LINUX:                       OS ABI Variant Handling.
(line  48)
* GDB_OSABI_NETBSD_AOUT:                 OS ABI Variant Handling.
(line  57)
* GDB_OSABI_NETBSD_ELF:                  OS ABI Variant Handling.
(line  60)
* GDB_OSABI_OPENBSD_ELF:                 OS ABI Variant Handling.
(line  63)
* GDB_OSABI_OSF1:                        OS ABI Variant Handling.
(line  45)
* GDB_OSABI_QNXNTO:                      OS ABI Variant Handling.
(line  84)
* GDB_OSABI_SOLARIS:                     OS ABI Variant Handling.
(line  42)
* GDB_OSABI_SVR4:                        OS ABI Variant Handling.
(line  36)
* GDB_OSABI_UNINITIALIZED:               OS ABI Variant Handling.
(line  29)
* GDB_OSABI_UNKNOWN:                     OS ABI Variant Handling.
(line  32)
* GDB_OSABI_WINCE:                       OS ABI Variant Handling.
(line  66)
* gdbarch:                               How an Architecture is Represented.
(line  19)
* gdbarch accessor functions:            Creating a New Architecture.
(line  14)
* gdbarch lookup:                        Looking Up an Existing Architecture.
(line   6)
* gdbarch register architecture functions: Register Architecture Functions & Variables.
(line   6)
* gdbarch register information functions: Register Information Functions.
(line   6)
* gdbarch_addr_bits_remove:              Defining Other Architecture Features.
(line  11)
* gdbarch_address_class_type_flags <1>:  Defining Other Architecture Features.
(line  43)
* gdbarch_address_class_type_flags_p:    Defining Other Architecture Features.
(line  52)
* gdbarch_address_class_type_flags_to_name <1>: Defining Other Architecture Features.
(line  56)
* gdbarch_address_class_type_flags_to_name_p: Defining Other Architecture Features.
(line  60)
* gdbarch_address_to_pointer <1>:        Defining Other Architecture Features.
(line  65)
(line 114)
(line 145)
* gdbarch_alloc:                         Creating a New Architecture.
(line   6)
* gdbarch_believe_pcc_promotion:         Defining Other Architecture Features.
(line  72)
* gdbarch_bits_big_endian:               Defining Other Architecture Features.
(line  77)
* gdbarch_breakpoint_from_pc:            Defining Other Architecture Features.
(line 106)
* gdbarch_call_dummy_location:           Defining Other Architecture Features.
(line 178)
* gdbarch_cannot_fetch_register:         Defining Other Architecture Features.
(line 184)
* gdbarch_cannot_store_register:         Defining Other Architecture Features.
(line 188)
* gdbarch_char_signed:                   Defining Other Architecture Features.
(line 461)
* gdbarch_convert_register_p <1>:        Defining Other Architecture Features.
(line 195)
* gdbarch_convert_register_p:            Register and Memory Data.
(line  30)
* gdbarch_data:                          Coding.              (line 133)
* gdbarch_data_register_post_init:       Coding.              (line 118)
* gdbarch_data_register_pre_init:        Coding.              (line 108)
* gdbarch_decr_pc_after_break:           Defining Other Architecture Features.
(line 205)
* gdbarch_deprecated_fp_regnum:          Defining Other Architecture Features.
(line 446)
* gdbarch_double_bit:                    Defining Other Architecture Features.
(line 471)
* gdbarch_dummy_id:                      Defining Other Architecture Features.
(line 523)
* gdbarch_dwarf2_reg_to_regnum:          Defining Other Architecture Features.
(line 216)
* gdbarch_ecoff_reg_to_regnum:           Defining Other Architecture Features.
(line 220)
* gdbarch_float_bit:                     Defining Other Architecture Features.
(line 475)
* gdbarch_fp0_regnum:                    Defining Other Architecture Features.
(line 200)
* gdbarch_get_longjmp_target <1>:        Defining Other Architecture Features.
(line 231)
* gdbarch_get_longjmp_target:            Algorithms.          (line 263)
* gdbarch_have_nonsteppable_watchpoint:  Algorithms.          (line 396)
* gdbarch_in_function_epilogue_p:        Defining Other Architecture Features.
(line 253)
* gdbarch_in_solib_return_trampoline:    Defining Other Architecture Features.
(line 259)
* gdbarch_info:                          Looking Up an Existing Architecture.
(line  22)
* gdbarch_init_osabi:                    OS ABI Variant Handling.
(line 125)
* gdbarch_int_bit:                       Defining Other Architecture Features.
(line 478)
* gdbarch_integer_to_address:            Defining Other Architecture Features.
(line 274)
* gdbarch_list_lookup_by_info:           Looking Up an Existing Architecture.
(line  22)
* gdbarch_long_bit:                      Defining Other Architecture Features.
(line 481)
* gdbarch_long_double_bit:               Defining Other Architecture Features.
(line 485)
* gdbarch_long_long_bit:                 Defining Other Architecture Features.
(line 489)
* gdbarch_lookup_osabi:                  OS ABI Variant Handling.
(line 119)
* gdbarch_memory_insert_breakpoint:      Defining Other Architecture Features.
(line 130)
* gdbarch_memory_remove_breakpoint:      Defining Other Architecture Features.
(line 130)
* gdbarch_osabi_name:                    OS ABI Variant Handling.
(line  97)
* gdbarch_pointer_to_address <1>:        Defining Other Architecture Features.
(line 295)
(line 105)
* gdbarch_print_insn:                    Defining Other Architecture Features.
(line 513)
* gdbarch_ptr_bit:                       Defining Other Architecture Features.
(line 493)
* gdbarch_push_dummy_call:               Defining Other Architecture Features.
(line 363)
* gdbarch_push_dummy_code:               Defining Other Architecture Features.
(line 375)
* gdbarch_register <1>:                  Adding a New Target. (line  40)
* gdbarch_register:                      How an Architecture is Represented.
(line  19)
* gdbarch_register_osabi:                OS ABI Variant Handling.
(line 103)
* gdbarch_register_osabi_sniffer:        OS ABI Variant Handling.
(line 112)
* gdbarch_register_to_value <1>:         Defining Other Architecture Features.
(line 301)
* gdbarch_register_to_value:             Register and Memory Data.
(line  46)
* gdbarch_return_value:                  Defining Other Architecture Features.
(line 394)
* gdbarch_sdb_reg_to_regnum:             Defining Other Architecture Features.
(line 390)
* gdbarch_short_bit:                     Defining Other Architecture Features.
(line 497)
* gdbarch_skip_permanent_breakpoint:     Defining Other Architecture Features.
(line 430)
* gdbarch_skip_trampoline_code:          Defining Other Architecture Features.
(line 441)
* gdbarch_stab_reg_to_regnum:            Defining Other Architecture Features.
(line 450)
* gdbarch_stabs_argument_has_addr:       Defining Other Architecture Features.
(line 359)
* gdbarch_tdep definition:               Creating a New Architecture.
(line  34)
* gdbarch_tdep when allocating new gdbarch: Creating a New Architecture.
(line   6)
* gdbarch_value_to_register <1>:         Defining Other Architecture Features.
(line 529)
* gdbarch_value_to_register:             Register and Memory Data.
(line  62)
* gdbarch_virtual_frame_pointer:         Defining Other Architecture Features.
(line 501)
* GDBINIT_FILENAME:                      Host Definition.     (line  74)
* generic host support:                  Host Definition.     (line  38)
* generic_elf_osabi_sniff_abi_tag_sections: OS ABI Variant Handling.
(line 133)
* get_frame_register:                    Stack Frames.        (line  15)
* get_frame_type:                        Stack Frames.        (line  22)
* hardware breakpoints:                  Algorithms.          (line 158)
* hardware watchpoints:                  Algorithms.          (line 280)
* HAVE_CONTINUABLE_WATCHPOINT:           Algorithms.          (line 402)
* HAVE_DOS_BASED_FILE_SYSTEM:            Coding.              (line 561)
* HAVE_STEPPABLE_WATCHPOINT:             Algorithms.          (line 386)
* host:                                  Overall Structure.   (line  50)
* host, adding:                          Host Definition.     (line  13)
* i386_cleanup_dregs:                    Algorithms.          (line 576)
* I386_DR_LOW_GET_STATUS:                Algorithms.          (line 489)
* I386_DR_LOW_SET_CONTROL:               Algorithms.          (line 479)
* i386_insert_hw_breakpoint:             Algorithms.          (line 564)
* i386_insert_watchpoint:                Algorithms.          (line 536)
* i386_region_ok_for_watchpoint:         Algorithms.          (line 514)
* i386_remove_hw_breakpoint:             Algorithms.          (line 564)
* i386_remove_watchpoint:                Algorithms.          (line 536)
* i386_stopped_by_watchpoint:            Algorithms.          (line 528)
* I386_USE_GENERIC_WATCHPOINTS:          Algorithms.          (line 461)
* in_dynsym_resolve_code:                Defining Other Architecture Features.
(line 263)
* inferior_added:                        GDB Observers.       (line 169)
* inferior_appeared:                     GDB Observers.       (line 173)
* inferior_created:                      GDB Observers.       (line  92)
* inferior_exit:                         GDB Observers.       (line 176)
* inferior_removed:                      GDB Observers.       (line 180)
* inner_than:                            Functions and Variable to Analyze Frames.
(line  30)
* innermost frame:                       Frame Handling Terminology.
(line  24)
* insert or remove hardware breakpoint:  Algorithms.          (line 234)
* insert or remove hardware watchpoint:  Algorithms.          (line 347)
* insert or remove software breakpoint:  Algorithms.          (line 211)
* IS_ABSOLUTE_PATH:                      Coding.              (line 572)
* IS_DIR_SEPARATOR:                      Coding.              (line 567)
* ISATTY:                                Host Definition.     (line  99)
* item output functions:                 User Interface.      (line 254)
* language parser:                       Language Support.    (line  25)
* language support:                      Language Support.    (line   6)
* legal papers for code contributions:   Debugging GDB.       (line  42)
* length_of_subexp:                      Language Support.    (line  58)
* libgdb:                                libgdb.              (line   9)
* libiberty library:                     Support Libraries.   (line  52)
* line wrap in output:                   Coding.              (line 191)
* lint:                                  Host Definition.     (line 119)
* list output functions:                 User Interface.      (line 131)
* LITTLE_BREAKPOINT:                     Defining Other Architecture Features.
(line 100)
* long long data type:                   Host Definition.     (line 106)
* longjmp debugging:                     Algorithms.          (line 258)
* lookup_symbol:                         Partial Symbol Tables.
(line  46)
* LSEEK_NOT_LINEAR:                      Host Definition.     (line 114)
* lval_type enumeration, for values.:    Values.              (line  19)
* make_cleanup:                          Coding.              (line  28)
* make_cleanup_ui_out_list_begin_end:    User Interface.      (line 247)
* make_cleanup_ui_out_tuple_begin_end:   User Interface.      (line 223)
* making a new release of gdb:           Releasing GDB.       (line   6)
* memory management for types:           Memory Management for Types.
(line   6)
* memory representation:                 Register and Memory Data.
(line   6)
* memory_changed:                        GDB Observers.       (line 185)
* minimal symbol table:                  Partial Symbol Tables.
(line  15)
* minsymtabs:                            Partial Symbol Tables.
(line  15)
* multi-arch data:                       Coding.              (line 100)
* NATDEPFILES:                           Native Debugging.    (line   8)
* native conditionals:                   Native Debugging.    (line  75)
* native debugging:                      Native Debugging.    (line   6)
* nesting level in ui_out functions:     User Interface.      (line 143)
* new year procedure:                    Start of New Year Procedure.
(line   6)
* new_objfile:                           GDB Observers.       (line 109)
* new_thread:                            GDB Observers.       (line 114)
* NEXT frame:                            Frame Handling Terminology.
(line  11)
* normal_stop:                           GDB Observers.       (line  76)
* normal_stop observer:                  GDB Observers.       (line  48)
* object file formats:                   Object File Formats. (line   6)
* observer pattern interface:            Algorithms.          (line 630)
* observers implementation rationale:    GDB Observers.       (line   9)
* obstacks:                              Support Libraries.   (line  69)
* op_print_tab:                          Language Support.    (line  91)
* opcodes library:                       Support Libraries.   (line  39)
* OS ABI variants:                       OS ABI Variant Handling.
(line   6)
* parse_exp_1:                           Language Support.    (line  97)
* partial symbol table:                  Partial Symbol Tables.
(line  18)
* pc_regnum:                             Register Architecture Functions & Variables.
(line  58)
* PE-COFF format:                        Object File Formats. (line  63)
* per-architecture module data:          Coding.              (line 100)
* pointer representation:                Pointers and Addresses.
(line   6)
* portability:                           Coding.              (line 535)
* portable file name handling:           Coding.              (line 552)
* porting to new machines:               Porting GDB.         (line   6)
* prefixify_subexp:                      Language Support.    (line  58)
* PREVIOUS frame:                        Frame Handling Terminology.
(line  14)
* print_float_info:                      Register Information Functions.
(line  80)
* print_registers_info:                  Register Information Functions.
(line  53)
* print_subexp:                          Language Support.    (line  91)
* print_vector_info:                     Register Information Functions.
(line  96)
* PRINTF_HAS_LONG_LONG:                  Host Definition.     (line 109)
* processor status register:             Register Architecture Functions & Variables.
(line  69)
* program counter <1>:                   Register Architecture Functions & Variables.
(line  58)
* program counter:                       Algorithms.          (line 158)
* prologue analysis:                     Algorithms.          (line  14)
* prologue cache:                        Prologue Caches.     (line  12)
* prologue of a function:                Prologue Caches.     (line   6)
* prologue-value.c:                      Algorithms.          (line  48)
* prompt:                                Host Definition.     (line  94)
* ps_regnum:                             Register Architecture Functions & Variables.
(line  69)
* pseudo-evaluation of function prologues: Algorithms.        (line  48)
* pseudo_register_read:                  Register Architecture Functions & Variables.
(line  29)
* pseudo_register_write:                 Register Architecture Functions & Variables.
(line  33)
* psymtabs:                              Partial Symbol Tables.
(line  11)
* push_dummy_call:                       Functions Creating Dummy Frames.
(line  13)
* push_dummy_code:                       Functions Creating Dummy Frames.
(line  57)
* raw register representation:           Raw and Cooked Registers.
(line   6)
* read_pc:                               Register Architecture Functions & Variables.
(line  10)
* readline library:                      Support Libraries.   (line  45)
* regcache_cooked_read:                  Register Caching.    (line  23)
* regcache_cooked_read_signed:           Register Caching.    (line  23)
* regcache_cooked_read_unsigned:         Register Caching.    (line  23)
* regcache_cooked_write:                 Register Caching.    (line  23)
* regcache_cooked_write_signed:          Register Caching.    (line  23)
* regcache_cooked_write_unsigned:        Register Caching.    (line  23)
* register caching:                      Register Caching.    (line   6)
* register data formats, converting:     Register and Memory Data.
(line   6)
* register representation:               Register and Memory Data.
(line   6)
* REGISTER_CONVERT_TO_RAW:               Defining Other Architecture Features.
(line 311)
* REGISTER_CONVERT_TO_VIRTUAL:           Defining Other Architecture Features.
(line 306)
* register_name:                         Register Information Functions.
(line  10)
* register_reggroup_p:                   Register Information Functions.
(line 110)
* register_type:                         Register Information Functions.
(line  33)
* regset_from_core_section:              Defining Other Architecture Features.
(line 316)
* regular expressions library:           Support Libraries.   (line 110)
* Release Branches:                      Versions and Branches.
(line  93)
* remote debugging support:              Host Definition.     (line  41)
* REMOTE_BPT_VECTOR:                     Defining Other Architecture Features.
(line 540)
* representation of architecture:        How an Architecture is Represented.
(line   6)
* representations, raw and cooked registers: Raw and Cooked Registers.
(line   6)
* representations, register and memory:  Register and Memory Data.
(line   6)
* requirements for GDB:                  Requirements.        (line   6)
* restart:                               Algorithms.          (line 600)
* running the test suite:                Testsuite.           (line  19)
* secondary symbol file:                 Symbol Reading.      (line  28)
* sentinel frame <1>:                    Frame Handling Terminology.
(line  52)
* sentinel frame:                        Stack Frames.        (line  22)
* SENTINEL_FRAME:                        Stack Frames.        (line  22)
(line   6)
* serial line support:                   Host Definition.     (line  41)
* set_gdbarch functions:                 Creating a New Architecture.
(line  14)
* set_gdbarch_bits_big_endian:           Defining Other Architecture Features.
(line  83)
* set_gdbarch_sofun_address_maybe_missing: Defining Other Architecture Features.
(line 330)
* SIGWINCH_HANDLER:                      Host Definition.     (line  78)
* SIGWINCH_HANDLER_BODY:                 Host Definition.     (line  82)
* skip_prologue:                         Functions and Variable to Analyze Frames.
(line  12)
* SKIP_SOLIB_RESOLVER:                   Defining Other Architecture Features.
(line 267)
* SLASH_STRING:                          Coding.              (line 589)
* sniffing:                              Frame Handling Terminology.
(line  46)
* software breakpoints:                  Algorithms.          (line 184)
* software watchpoints:                  Algorithms.          (line 280)
* SOFTWARE_SINGLE_STEP:                  Defining Other Architecture Features.
(line 324)
* SOFTWARE_SINGLE_STEP_P:                Defining Other Architecture Features.
(line 320)
* SOLIB_ADD:                             Native Debugging.    (line  86)
* SOLIB_CREATE_INFERIOR_HOOK:            Native Debugging.    (line  92)
* solib_loaded:                          GDB Observers.       (line  99)
* solib_unloaded:                        GDB Observers.       (line 104)
* SOM debugging info:                    Debugging File Formats.
(line  67)
* SOM format:                            Object File Formats. (line  82)
* source code formatting:                Coding.              (line 323)
* sp_regnum:                             Register Architecture Functions & Variables.
(line  49)
(line   6)
* stabs debugging info:                  Debugging File Formats.
(line  12)
* stack frame, definition of base of a frame: Frame Handling Terminology.
(line  28)
* stack frame, definition of innermost frame: Frame Handling Terminology.
(line  24)
* stack frame, definition of NEXT frame: Frame Handling Terminology.
(line  11)
* stack frame, definition of PREVIOUS frame: Frame Handling Terminology.
(line  14)
* stack frame, definition of sentinel frame: Frame Handling Terminology.
(line  52)
* stack frame, definition of sniffing:   Frame Handling Terminology.
(line  46)
* stack frame, definition of THIS frame: Frame Handling Terminology.
(line   9)
* stack frame, definition of unwinding:  Frame Handling Terminology.
(line  41)
* stack pointer:                         Register Architecture Functions & Variables.
(line  49)
* START_INFERIOR_TRAPS_EXPECTED:         Native Debugging.    (line  96)
* status register:                       Register Architecture Functions & Variables.
(line  69)
* STOPPED_BY_WATCHPOINT:                 Algorithms.          (line 408)
(line  70)
* struct:                                GDB Observers.       (line  62)
* struct gdbarch creation:               Creating a New Architecture.
(line   6)
* struct regcache:                       Register Caching.    (line  10)
* struct value, converting register contents to: Register and Memory Data.
(line   6)
* submitting patches:                    Debugging GDB.       (line  30)
* sym_fns structure:                     Symbol Reading.      (line  18)
* symbol files:                          Symbol Reading.      (line   6)
* symbol lookup:                         Partial Symbol Tables.
(line  37)
(line 454)
* symtabs:                               Partial Symbol Tables.
(line   8)
* system dependencies:                   Coding.              (line 539)
* table output functions:                User Interface.      (line 131)
* target:                                Overall Structure.   (line  50)
* target architecture definition:        Target Architecture Definition.
(line   6)
* target dependent files:                Adding a New Target. (line   8)
* target descriptions:                   Target Descriptions. (line   6)
(line   6)
* target descriptions, implementation:   Target Descriptions Implementation.
(line   6)
* target vector:                         Target Vector Definition.
(line   6)
* TARGET_CAN_USE_HARDWARE_WATCHPOINT:    Algorithms.          (line 333)
* target_changed:                        GDB Observers.       (line  82)
* TARGET_CHAR_BIT:                       Defining Other Architecture Features.
(line 458)
* target_insert_breakpoint:              Algorithms.          (line 211)
* target_insert_hw_breakpoint:           Algorithms.          (line 234)
* target_insert_watchpoint:              Algorithms.          (line 347)
* TARGET_REGION_OK_FOR_HW_WATCHPOINT:    Algorithms.          (line 343)
* target_remove_breakpoint:              Algorithms.          (line 211)
* target_remove_hw_breakpoint:           Algorithms.          (line 234)
* target_remove_watchpoint:              Algorithms.          (line 347)
* target_resumed:                        GDB Observers.       (line 129)
* targets:                               Existing Targets.    (line   6)
* TCP remote support:                    Host Definition.     (line  57)
* terminal device:                       Host Definition.     (line  97)
* test suite:                            Testsuite.           (line   6)
* test suite organization:               Testsuite.           (line 195)
* test_notification:                     GDB Observers.       (line 193)
* Testsuite Configuration:               Testsuite.           (line 167)
* THIS frame:                            Frame Handling Terminology.
(line   9)
* thread_exit:                           GDB Observers.       (line 117)
* thread_ptid_changed:                   GDB Observers.       (line 165)
* thread_stop_requested:                 GDB Observers.       (line 122)
* tracepoint_created:                    GDB Observers.       (line 148)
* tracepoint_deleted:                    GDB Observers.       (line 152)
* tracepoint_modified:                   GDB Observers.       (line 156)
* tuple output functions:                User Interface.      (line 131)
* type codes:                            Types.               (line  17)
* TYPE_OBJFILE:                          Memory Management for Types.
(line   6)
* types:                                 Coding.              (line 405)
* ui_out functions:                      User Interface.      (line  47)
* ui_out functions, usage examples:      User Interface.      (line 398)
* ui_out_field_core_addr:                User Interface.      (line 287)
* ui_out_field_fmt:                      User Interface.      (line 261)
* ui_out_field_fmt_int:                  User Interface.      (line 280)
* ui_out_field_int:                      User Interface.      (line 273)
* ui_out_field_skip:                     User Interface.      (line 352)
* ui_out_field_stream:                   User Interface.      (line 320)
* ui_out_field_string:                   User Interface.      (line 291)
* ui_out_flush:                          User Interface.      (line 392)
* ui_out_list_begin:                     User Interface.      (line 234)
* ui_out_list_end:                       User Interface.      (line 240)
* ui_out_message:                        User Interface.      (line 376)
* ui_out_spaces:                         User Interface.      (line 371)
* ui_out_stream_delete:                  User Interface.      (line 315)
* ui_out_stream_new:                     User Interface.      (line 309)
* ui_out_table_begin:                    User Interface.      (line 165)
* ui_out_table_body:                     User Interface.      (line 191)
* ui_out_table_end:                      User Interface.      (line 194)
* ui_out_table_header:                   User Interface.      (line 178)
* ui_out_text:                           User Interface.      (line 358)
* ui_out_tuple_begin:                    User Interface.      (line 210)
* ui_out_tuple_end:                      User Interface.      (line 216)
* ui_out_wrap_hint:                      User Interface.      (line 382)
* unwind frame:                          Stack Frames.        (line   9)
* unwind_dummy_id:                       Functions Creating Dummy Frames.
(line  38)
* unwind_pc:                             Functions to Access Frame Data.
(line  11)
* unwind_sp:                             Functions to Access Frame Data.
(line  27)
* unwinding:                             Frame Handling Terminology.
(line  41)
* using ui_out functions:                User Interface.      (line 398)
* value structure:                       Values.              (line   9)
(line  84)
(line  93)
* values:                                Values.              (line   9)
* VEC:                                   Support Libraries.   (line 131)
* vendor branches:                       Versions and Branches.
(line 108)
* void:                                  GDB Observers.       (line  67)
* volatile:                              Host Definition.     (line 122)
* watchpoints:                           Algorithms.          (line 274)
* watchpoints, on x86:                   Algorithms.          (line 449)
* watchpoints, with threads:             Algorithms.          (line 425)

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