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
```
{
        UniValue obj(UniValue::VOBJ);
        CScript subscript;
        CRIPEMD160 hasher;
        uint160 hash;
        hasher.Write(id.begin(), 32).Finalize(hash.begin());
        if (provider && provider->GetCScript(CScriptID(hash), subscript)) {
            ProcessSubScript(subscript, obj);
        }
        return obj;
    }
    UniValue operator()(const WitnessUnknown& id) const { return UniValue(UniValue::VOBJ); }
};
static UniValue DescribeWalletAddress(const CWallet* const pwallet, const CTxDestination& dest)
{
    UniValue ret(UniValue::VOBJ);
    UniValue detail = DescribeAddress(dest);
    CScript script = GetScriptForDestination(dest);
    std::unique_ptr<SigningProvider> provider = nullptr;
    if (pwallet) {
        provider = pwallet->GetSolvingProvider(script);
    }
    ret.pushKVs(detail);
    ret.pushKVs(boost::apply_visitor(DescribeWalletAddressVisitor(provider.get()), dest));
    return ret;
}
static UniValue AddressBookDataToJSON(const CAddressBookData& data, const bool verbose)