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{"walletprocesspsbt",
                "\nUpdate a PSBT with input information from our wallet and then sign inputs\n"
                "that we can sign for." +
        HELP_REQUIRING_PASSPHRASE,
                {
                    {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO, "The transaction base64 string"},
                    {"sign", RPCArg::Type::BOOL,  "true", "Also sign the transaction when updating"},
                    {"sighashtype", RPCArg::Type::STR,  "ALL", "The signature hash type to sign with if not specified by the PSBT. Must be one of\n"
            "       \"ALL\"\n"
            "       \"NONE\"\n"
            "       \"SINGLE\"\n"
            "       \"ALL|ANYONECANPAY\"\n"
            "       \"NONE|ANYONECANPAY\"\n"
            "       \"SINGLE|ANYONECANPAY\""},
                    {"bip32derivs", RPCArg::Type::BOOL,  "true", "Include BIP 32 derivation paths for public keys if we know them"},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR, "psbt", "The base64-encoded partially signed transaction"},
                        {RPCResult::Type::BOOL, "complete", "If the transaction has a complete set of signatures"},
                    }
                },
                RPCExamples{
                    HelpExampleCli("walletprocesspsbt", "\"psbt\"")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{