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
```
CWallet* const pwallet = wallet.get();
    int64_t nSleepTime;
    int64_t relock_time;
    
    LOCK(pwallet->m_unlock_mutex);
    {
        LOCK(pwallet->cs_wallet);
        if (!pwallet->IsCrypted()) {
            throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletpassphrase was called.");
        }
        
        SecureString strWalletPass;
        strWalletPass.reserve(100);
        
        
        strWalletPass = request.params[0].get_str().c_str();
        
        nSleepTime = request.params[1].get_int64();
        
        if (nSleepTime < 0) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Timeout cannot be negative.");
        }
        
        constexpr int64_t MAX_SLEEP_TIME = 100000000; 
        if (nSleepTime > MAX_SLEEP_TIME) {
            nSleepTime = MAX_SLEEP_TIME;
        }
        if (strWalletPass.empty()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "passphrase can not be empty");
        }