@jonasschnelli wrote in #14979:
> #14573 broke < Qt5.6 compatibility due to calling the lambda version of `addAction` that was added in Qt5.6.

We currently [support](https://github.com/bitcoin/bitcoin/blob/master/doc/dependencies.md) QT >=5.2, but hardly anyone tests with that. If we make one of the Travis machines use it, we should have a better change of catching this.

See also discussion about minimum QT version in #13478 
{
    
    int nIn = 0;
    for (const auto& txout : txouts)
    {
        if (!DummySignInput(txNew.vin[nIn], txout, use_max_sig)) {
            return false;
        }
        nIn++;
    }
    return true;
}
int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig)
{
    std::vector<CTxOut> txouts;
    
    
    
    for (const CTxIn& input : tx.vin) {
        const auto mi = wallet->mapWallet.find(input.prevout.hash);
        if (mi == wallet->mapWallet.end()) {
            return -1;
        }
        assert(input.prevout.n < mi->second.tx->vout.size());
        txouts.emplace_back(mi->second.tx->vout[input.prevout.n]);
    }
    return CalculateMaximumSignedTxSize(tx, wallet, txouts, use_max_sig);
}
int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig)