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 strMessage = request.params[1].get_str();
    CTxDestination dest = DecodeDestination(strAddress);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Invalid address");
    }
    const PKHash *pkhash = boost::get<PKHash>(&dest);
    if (!pkhash) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
    }
    std::string signature;
    SigningResult err = pwallet->SignMessage(strMessage, *pkhash, signature);
    if (err == SigningResult::SIGNING_FAILED) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, SigningResultString(err));
    } else if (err != SigningResult::OK){
        throw JSONRPCError(RPC_WALLET_ERROR, SigningResultString(err));
    }
    return signature;
},
    };
}
static CAmount GetReceived(const CWallet& wallet, const UniValue& params, bool by_label) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
    std::set<CTxDestination> address_set;
    if (by_label) {
        
        std::string label = LabelFromValue(params[0]);
        address_set = wallet.GetLabelAddresses(label);
    } else {
        
        CTxDestination dest = DecodeDestination(params[0].get_str());