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
```
{
    return RPCHelpMan{"listwallets",
                "Returns a list of currently loaded wallets.\n"
                "For full information on the wallet, use \"getwalletinfo\"\n",
                {},
                RPCResult{
                    RPCResult::Type::ARR, "", "",
                    {
                        {RPCResult::Type::STR, "walletname", "the wallet name"},
                    }
                },
                RPCExamples{
                    HelpExampleCli("listwallets", "")
            + HelpExampleRpc("listwallets", "")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    UniValue obj(UniValue::VARR);
    for (const std::shared_ptr<CWallet>& wallet : GetWallets()) {
        LOCK(wallet->cs_wallet);
        obj.push_back(wallet->GetName());
    }
    return obj;
},
    };
}
static RPCHelpMan loadwallet()