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
```
{
    return RPCHelpMan{"sendmany",
                "\nSend multiple times. Amounts are double-precision floating point numbers." +
        HELP_REQUIRING_PASSPHRASE,
                {
                    {"dummy", RPCArg::Type::STR, RPCArg::Optional::NO, "Must be set to \"\" for backwards compatibility.", "\"\""},
                    {"amounts", RPCArg::Type::OBJ, RPCArg::Optional::NO, "The addresses and amounts",
                        {
                            {"address", RPCArg::Type::AMOUNT, RPCArg::Optional::NO, "The bitcoin address is the key, the numeric amount (can be string) in " + CURRENCY_UNIT + " is the value"},
                        },
                    },
                    {"minconf", RPCArg::Type::NUM, RPCArg::Optional::OMITTED_NAMED_ARG, "Ignored dummy value"},
                    {"comment", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "A comment"},
                    {"subtractfeefrom", RPCArg::Type::ARR, RPCArg::Optional::OMITTED_NAMED_ARG, "The addresses.\n"
                                       "The fee will be equally deducted from the amount of each selected address.\n"
                                       "Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
                                       "If no addresses are specified here, the sender pays the fee.",
                        {
                            {"address", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Subtract fee from this address"},
                        },
                    },
                    {"replaceable", RPCArg::Type::BOOL,  "wallet default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
                    {"conf_target", RPCArg::Type::NUM,  "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
                                       "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},