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
```
if (filter_label->empty()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Label argument must be a valid label name or \"*\".");
        }
    }
    int nCount = 10;
    if (!request.params[1].isNull())
        nCount = request.params[1].get_int();
    int nFrom = 0;
    if (!request.params[2].isNull())
        nFrom = request.params[2].get_int();
    isminefilter filter = ISMINE_SPENDABLE;
    if (ParseIncludeWatchonly(request.params[3], *pwallet)) {
        filter |= ISMINE_WATCH_ONLY;
    }
    if (nCount < 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative count");
    if (nFrom < 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative from");
    UniValue ret(UniValue::VARR);
    {
        LOCK(pwallet->cs_wallet);
        const CWallet::TxItems & txOrdered = pwallet->wtxOrdered;
        
        for (CWallet::TxItems::const_reverse_iterator it = txOrdered.rbegin(); it != txOrdered.rend(); ++it)
        {
            CWalletTx *const pwtx = (*it).second;
            ListTransactions(pwallet, *pwtx, 0, true, ret, filter, filter_label);
            if ((int)ret.size() >= (nCount+nFrom)) break;
        }
    }