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
```
bilingual_str error;
    Optional<bool> load_on_start = request.params[6].isNull() ? nullopt : Optional<bool>(request.params[6].get_bool());
    std::shared_ptr<CWallet> wallet = CreateWallet(*context.chain, request.params[0].get_str(), load_on_start, options, status, error, warnings);
    if (!wallet) {
        RPCErrorCode code = status == DatabaseStatus::FAILED_ENCRYPT ? RPC_WALLET_ENCRYPTION_FAILED : RPC_WALLET_ERROR;
        throw JSONRPCError(code, error.original);
    }
    UniValue obj(UniValue::VOBJ);
    obj.pushKV("name", wallet->GetName());
    obj.pushKV("warning", Join(warnings, Untranslated("\n")).original);
    return obj;
},
    };
}
static RPCHelpMan unloadwallet()
{
    return RPCHelpMan{"unloadwallet",
                "Unloads the wallet referenced by the request endpoint otherwise unloads the wallet specified in the argument.\n"
                "Specifying the wallet name on a wallet endpoint is invalid.",
                {
                    {"wallet_name", RPCArg::Type::STR,  "the wallet name from the RPC request", "The name of the wallet to unload."},
                    {"load_on_startup", RPCArg::Type::BOOL,  "null", "Save wallet name to persistent settings and load on startup. True to add wallet to startup list, false to remove, null to leave unchanged."},
                },
                RPCResult{RPCResult::Type::OBJ, "", "", {
                    {RPCResult::Type::STR, "warning", "Warning message if wallet was not unloaded cleanly."},
                }},
                RPCExamples{
                    HelpExampleCli("unloadwallet", "wallet_name")
            + HelpExampleRpc("unloadwallet", "wallet_name")
                },