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{"sethdseed",
                "\nSet or generate a new HD wallet seed. Non-HD wallets will not be upgraded to being a HD wallet. Wallets that are already\n"
                "HD will have a new HD seed set so that new keys added to the keypool will be derived from this new seed.\n"
                "\nNote that you will need to MAKE A NEW BACKUP of your wallet after setting the HD wallet seed." +
        HELP_REQUIRING_PASSPHRASE,
                {
                    {"newkeypool", RPCArg::Type::BOOL,  "true", "Whether to flush old unused addresses, including change addresses, from the keypool and regenerate it.\n"
                                         "If true, the next address from getnewaddress and change address from getrawchangeaddress will be from this new seed.\n"
                                         "If false, addresses (including change addresses if the wallet already had HD Chain Split enabled) from the existing\n"
                                         "keypool will be used until it has been depleted."},
                    {"seed", RPCArg::Type::STR,  "random seed", "The WIF private key to use as the new HD seed.\n"
                                         "The seed value can be retrieved using the dumpwallet command. It is the private key marked hdseed=1"},
                },
                RPCResult{RPCResult::Type::NONE, "", ""},
                RPCExamples{
                    HelpExampleCli("sethdseed", "")
            + HelpExampleCli("sethdseed", "false")
            + HelpExampleCli("sethdseed", "true \"wifkey\"")
            + HelpExampleRpc("sethdseed", "true, \"wifkey\"")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    if (!wallet) return NullUniValue;
    CWallet* const pwallet = wallet.get();
    LegacyScriptPubKeyMan& spk_man = EnsureLegacyScriptPubKeyMan(*pwallet, true);
    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Cannot set a HD seed to a wallet with private keys disabled");
    }