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
```
RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::ARR, "wallets", "",
                        {
                            {RPCResult::Type::OBJ, "", "",
                            {
                                {RPCResult::Type::STR, "name", "The wallet name"},
                            }},
                        }},
                    }
                },
                RPCExamples{
                    HelpExampleCli("listwalletdir", "")
            + HelpExampleRpc("listwalletdir", "")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    UniValue wallets(UniValue::VARR);
    for (const auto& path : ListWalletDir()) {
        UniValue wallet(UniValue::VOBJ);
        wallet.pushKV("name", path.string());
        wallets.push_back(wallet);
    }
    UniValue result(UniValue::VOBJ);
    result.pushKV("wallets", wallets);
    return result;
},
    };
}
static RPCHelpMan listwallets()