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
```
{
            std::string flags = "";
            for (auto& it : WALLET_FLAG_MAP)
                if (it.second & MUTABLE_WALLET_FLAGS)
                    flags += (flags == "" ? "" : ", ") + it.first;
    return RPCHelpMan{"setwalletflag",
                "\nChange the state of the given wallet flag for a wallet.\n",
                {
                    {"flag", RPCArg::Type::STR, RPCArg::Optional::NO, "The name of the flag to change. Current available flags: " + flags},
                    {"value", RPCArg::Type::BOOL,  "true", "The new state."},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR, "flag_name", "The name of the flag that was modified"},
                        {RPCResult::Type::BOOL, "flag_state", "The new state of the flag"},
                        {RPCResult::Type::STR, "warnings", "Any warnings associated with the change"},
                    }
                },
                RPCExamples{
                    HelpExampleCli("setwalletflag", "avoid_reuse")
                  + HelpExampleRpc("setwalletflag", "\"avoid_reuse\"")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);