Have this warning while building current master (0bd4929cd00e91bf4137f43b097cd62f72f503e4) on one test machine.
```
wallet/rpcwallet.cpp: In function 'rescanblockchain()::<lambda(const RPCHelpMan&, const JSONRPCRequest&)>':
wallet/rpcwallet.cpp:3596:19: warning: '*((void*)& stop_height +4)' may be used uninitialized in this function [-Wmaybe-uninitialized]
 3596 |     Optional<int> stop_height;
      |                   ^~~~~~~~~~~
```
```
$ gcc --version
gcc (Gentoo 9.2.0-r2 p3) 9.2.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ uname -a
Linux red-box 4.19.72-gentoo #2 SMP Sun Sep 22 03:00:01 EEST 2019 x86_64 Intel(R) Pentium(R) CPU N3710 @ 1.60GHz GenuineIntel GNU/Linux
```
},
                                },
                            {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "",
                                {
                                    {"data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "A key-value pair. The key must be \"data\", the value is hex-encoded data"},
                                },
                            },
                        },
                    },
                    {"locktime", RPCArg::Type::NUM,  "0", "Raw locktime. Non-0 value also locktime-activates inputs"},
                    {"options", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "",
                        {
                            {"add_inputs", RPCArg::Type::BOOL,  "false", "If inputs are specified, automatically include more if they are not enough."},
                            {"changeAddress", RPCArg::Type::STR_HEX,  "pool address", "The bitcoin address to receive the change"},
                            {"changePosition", RPCArg::Type::NUM,  "random", "The index of the change output"},
                            {"change_type", RPCArg::Type::STR,  "set by -changetype", "The output type to use. Only valid if changeAddress is not specified. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\"."},
                            {"includeWatching", RPCArg::Type::BOOL,  "true for watch-only wallets, otherwise false", "Also select inputs which are watch only"},
                            {"lockUnspents", RPCArg::Type::BOOL,  "false", "Lock selected unspent outputs"},
                            {"feeRate", RPCArg::Type::AMOUNT,  "not set: makes wallet determine the fee", "Set a specific fee rate in " + CURRENCY_UNIT + "/kB"},
                            {"subtractFeeFromOutputs", RPCArg::Type::ARR,  "empty array", "The outputs to subtract the fee from.\n"
                                                          "The fee will be equally deducted from the amount of each specified output.\n"
                                                          "Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
                                                          "If no outputs are specified here, the sender pays the fee.",
                                {
                                    {"vout_index", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "The zero-based output index, before a change output is added."},
                                },
                            },
                            {"replaceable", RPCArg::Type::BOOL,  "wallet default", "Marks this transaction as BIP125 replaceable.\n"
                                                          "Allows this transaction to be replaced by a transaction with higher fees"},
                            {"conf_target", RPCArg::Type::NUM,  "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"