content: {-
  (c) The University of Glasgow 2006
  (c) The GRASP Project, Glasgow University, 1992-2000
  
  Defines basic functions for printing error messages.
  
  It's hard to put these functions anywhere else without causing
  some unnecessary loops in the module dependency graph.
  -}
  
  {-# LANGUAGE CPP, DeriveDataTypeable, ScopedTypeVariables, LambdaCase #-}
  
  module Eta.Utils.Panic (
       GhcException(..), showGhcException,
       throwGhcException, throwGhcExceptionIO,
       handleGhcException,
       progName,
       pgmError,
  
       panic, sorry, panicFastInt, assertPanic, trace,
       panicDoc, sorryDoc, panicDocFastInt, pgmErrorDoc,
  
       Exception.Exception(..), showException, safeShowException, try, tryMost, throwTo,
  
       withSignalHandlers
  ) where
  
  #include "HsVersions.h"
  
  import {-# SOURCE #-} Eta.Utils.Outputable (SDoc)
  
  import Eta.Main.Constants
  import Eta.Utils.FastTypes
  import Eta.Utils.Exception
  import qualified Eta.Utils.Exception as Exception
  
  import Control.Concurrent
  import Control.Monad.IO.Class
  import Data.Dynamic
  import Debug.Trace        ( trace )
  import System.IO.Unsafe
  import System.Exit
  import System.Environment
  
  #ifndef mingw32_HOST_OS
  import System.Posix.Signals as S
  #endif
  
  #if defined(mingw32_HOST_OS)
  import GHC.ConsoleHandler as S
  #endif
  
  import GHC.Stack
  import System.Mem.Weak  ( deRefWeak )
  
  -- | GHC's own exception type
  --   error messages all take the form:
  --
  --  @
  --      <location>: <error>
  --  @
  --
  --   If the location is on the command line, or in GHC itself, then
  --   <location>="ghc".  All of the error types below correspond to
  --   a <location> of "ghc", except for ProgramError (where the string is
  --  assumed to contain a location already, so we don't print one).
  
  data GhcException
    = PhaseFailed  String         -- name of phase
                   ExitCode       -- an external phase (eg. cpp) failed
  
    -- | Some other fatal signal (SIGHUP,SIGTERM)
    | Signal Int
  
    -- | Prints the short usage msg after the error
    | UsageError   String
  
    -- | A problem with the command line arguments, but don't print usage.
    | CmdLineError String
  
    -- | The 'impossible' happened.
    | Panic        String
    | PprPanic     String SDoc
  
    -- | The user tickled something that's known not to work yet,
    --   but we're not counting it as a bug.
    | Sorry        String
    | PprSorry     String SDoc
  
    -- | An installation problem.
    | InstallationError String
  
    -- | An error in the user's code, probably.
    | ProgramError    String
    | PprProgramError String SDoc
    deriving (Typeable)
  
  instance Exception GhcException
  
  instance Show GhcException where
    showsPrec _ e@(ProgramError _) = showGhcException e
    showsPrec _ e@(CmdLineError _) = showString "<command line>: " . showGhcException e
    showsPrec _ e = showString progName . showString ": " . showGhcException e
  
  
  -- | The name of this GHC.
  progName :: String
  progName = unsafePerformIO (getProgName)
  {-# NOINLINE progName #-}
  
  
  -- | Short usage information to display when we are given the wrong cmd line arguments.
  short_usage :: String
  short_usage = "Usage: For basic information, try the `--help' option."
  
  
  -- | Show an exception as a string.
  showException :: Exception e => e -> String
  showException = show
  
  -- | Show an exception which can possibly throw other exceptions.
  -- Used when displaying exception thrown within TH code.
  safeShowException :: Exception e => e -> IO String
  safeShowException e = do
      -- ensure the whole error message is evaluated inside try
      r <- try (return $! forceList (showException e))
      case r of
          Right msg -> return msg
          Left e' -> safeShowException (e' :: SomeException)
      where
          forceList [] = []
          forceList xs@(x : xt) = x `seq` forceList xt `seq` xs
  
  -- | Append a description of the given exception to this string.
  showGhcException :: GhcException -> String -> String
  showGhcException exception
   = case exception of
          UsageError str
           -> showString str . showChar '\n' . showString short_usage
  
          PhaseFailed phase code
           -> showString "phase `" . showString phase .
              showString "' failed (exitcode = " . shows (int_code code) .
              showString ")"
  
          CmdLineError str        -> showString str
          PprProgramError str  _  ->
              showGhcException (ProgramError (str ++ "\n<<details unavailable>>"))
          ProgramError str        -> showString str
          InstallationError str   -> showString str
          Signal n                -> showString "signal: " . shows n
  
          PprPanic  s _ ->
              showGhcException (Panic (s ++ "\n<<details unavailable>>"))
          Panic s
           -> showString $
                  "panic! (the 'impossible' happened)\n"
                  ++ "  (Eta version " ++ cProjectVersion ++ "):\n\t"
                  ++ s ++ "\n\n"
                  ++ "Please report this as a Eta bug: " ++ cProjectIssueReportURL ++ "\n"
  
          PprSorry  s _ ->
              showGhcException (Sorry (s ++ "\n<<details unavailable>>"))
          Sorry s
           -> showString $
                  "sorry! (unimplemented feature or known bug)\n"
                   ++ "  (Eta version " ++ cProjectVersion ++ "):\n\t"
                   ++ s ++ "\n"
  
    where int_code code =
            case code of
                  ExitSuccess   -> (0::Int)
                  ExitFailure x -> x
  
  
  throwGhcException :: GhcException -> a
  throwGhcException = Exception.throw
  
  throwGhcExceptionIO :: GhcException -> IO a
  throwGhcExceptionIO = Exception.throwIO
  
  handleGhcException :: ExceptionMonad m => (GhcException -> m a) -> m a -> m a
  handleGhcException = ghandle
  
  
  -- | Panics and asserts.
  panic, sorry, pgmError :: String -> a
  panic    x = unsafeDupablePerformIO $ do
     stack <- ccsToStrings =<< getCurrentCCS x
     if null stack
        then throwGhcException (Panic x)
        else throwGhcException (Panic (x ++ '\n' : renderStack stack))
  
  sorry    x = throwGhcException (Sorry x)
  pgmError x = throwGhcException (ProgramError x)
  
  panicDoc, sorryDoc, pgmErrorDoc :: String -> SDoc -> a
  panicDoc    x doc = throwGhcException (PprPanic        x doc)
  sorryDoc    x doc = throwGhcException (PprSorry        x doc)
  pgmErrorDoc x doc = throwGhcException (PprProgramError x doc)
  
  
  -- | Panic while pretending to return an unboxed int.
  --   You can't use the regular panic functions in expressions
  --   producing unboxed ints because they have the wrong kind.
  panicFastInt :: String -> FastInt
  panicFastInt s = case (panic s) of () -> _ILIT(0)
  
  panicDocFastInt :: String -> SDoc -> FastInt
  panicDocFastInt s d = case (panicDoc s d) of () -> _ILIT(0)
  
  
  -- | Throw an failed assertion exception for a given filename and line number.
  assertPanic :: String -> Int -> a
  assertPanic file line =
    Exception.throw (Exception.AssertionFailed
             ("ASSERT failed! file " ++ file ++ ", line " ++ show line))
  
  
  -- | Like try, but pass through UserInterrupt and Panic exceptions.
  --   Used when we want soft failures when reading interface files, for example.
  --   TODO: I'm not entirely sure if this is catching what we really want to catch
  tryMost :: IO a -> IO (Either SomeException a)
  tryMost action = do r <- try action
                      case r of
                          Left se ->
                              case fromException se of
                                  -- Some GhcException's we rethrow,
                                  Just (Signal _)  -> throwIO se
                                  Just (Panic _)   -> throwIO se
                                  -- others we return
                                  Just _           -> return (Left se)
                                  Nothing ->
                                      case fromException se of
                                          -- All IOExceptions are returned
                                          Just (_ :: IOException) ->
                                              return (Left se)
                                          -- Anything else is rethrown
                                          Nothing -> throwIO se
                          Right v -> return (Right v)
  
  -- | We use reference counting for signal handlers
  {-# NOINLINE signalHandlersRefCount #-}
  #if !defined(mingw32_HOST_OS)
  signalHandlersRefCount :: MVar (Word, Maybe (S.Handler,S.Handler
                                              ,S.Handler,S.Handler))
  #else
  signalHandlersRefCount :: MVar (Word, Maybe S.Handler)
  #endif
  signalHandlersRefCount = unsafePerformIO $ newMVar (0,Nothing)
  
  
  -- | Temporarily install standard signal handlers for catching ^C, which just
  -- throw an exception in the current thread.
  withSignalHandlers :: (ExceptionMonad m, MonadIO m) => m a -> m a
  withSignalHandlers act = do
    main_thread <- liftIO myThreadId
    wtid <- liftIO (mkWeakThreadId main_thread)
  
    let
        interrupt = do
          r <- deRefWeak wtid
          case r of
            Nothing -> return ()
            Just t  -> throwTo t UserInterrupt
  
  #if !defined(mingw32_HOST_OS)
    let installHandlers = do
          let installHandler' a b = installHandler a b Nothing
          hdlQUIT <- installHandler' sigQUIT  (Catch interrupt)
          hdlINT  <- installHandler' sigINT   (Catch interrupt)
          -- see #3656; in the future we should install these automatically for
          -- all Haskell programs in the same way that we install a ^C handler.
          let fatal_signal n = throwTo main_thread (Signal (fromIntegral n))
          hdlHUP  <- installHandler' sigHUP   (Catch (fatal_signal sigHUP))
          hdlTERM <- installHandler' sigTERM  (Catch (fatal_signal sigTERM))
          return (hdlQUIT,hdlINT,hdlHUP,hdlTERM)
  
    let uninstallHandlers (hdlQUIT,hdlINT,hdlHUP,hdlTERM) = do
          _ <- installHandler sigQUIT  hdlQUIT Nothing
          _ <- installHandler sigINT   hdlINT  Nothing
          _ <- installHandler sigHUP   hdlHUP  Nothing
          _ <- installHandler sigTERM  hdlTERM Nothing
          return ()
  #else
    -- GHC 6.3+ has support for console events on Windows
    -- NOTE: running GHCi under a bash shell for some reason requires
    -- you to press Ctrl-Break rather than Ctrl-C to provoke
    -- an interrupt.  Ctrl-C is getting blocked somewhere, I don't know
    -- why --SDM 17/12/2004
    let sig_handler ControlC = interrupt
        sig_handler Break    = interrupt
        sig_handler _        = return ()
  
    let installHandlers   = installHandler (Catch sig_handler)
    let uninstallHandlers = installHandler -- directly install the old handler
  #endif
  
    -- install signal handlers if necessary
    let mayInstallHandlers = liftIO $ modifyMVar_ signalHandlersRefCount $ \case
          (0,Nothing)     -> do
            hdls <- installHandlers
            return (1,Just hdls)
          (c,oldHandlers) -> return (c+1,oldHandlers)
  
    -- uninstall handlers if necessary
    let mayUninstallHandlers = liftIO $ modifyMVar_ signalHandlersRefCount $ \case
          (1,Just hdls)   -> do
            _ <- uninstallHandlers hdls
            return (0,Nothing)
          (c,oldHandlers) -> return (c-1,oldHandlers)
  
    mayInstallHandlers
    act `gfinally` mayUninstallHandlers
  