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
```
[&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
        {
            RPCTypeCheck(request.params, {
                UniValueType(), 
                UniValue::VNUM,
                UniValue::VSTR,
                UniValue::VOBJ
                }, true
            );
            std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
            if (!wallet) return NullUniValue;
            CWallet* const pwallet = wallet.get();
            UniValue options = request.params[3];
            if (options.exists("feeRate") || options.exists("fee_rate") || options.exists("estimate_mode") || options.exists("conf_target")) {
                if (!request.params[1].isNull() || !request.params[2].isNull()) {
                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Use either conf_target and estimate_mode or the options dictionary to control fee rate");
                }
            } else {
                options.pushKV("conf_target", request.params[1]);
                options.pushKV("estimate_mode", request.params[2]);
            }
            if (!options["conf_target"].isNull() && (options["estimate_mode"].isNull() || (options["estimate_mode"].get_str() == "unset"))) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Specify estimate_mode");
            }
            if (options.exists("changeAddress")) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Use change_address");
            }
            if (options.exists("changePosition")) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Use change_position");
            }