Merge #9343: Don't create change at dust limit

6171826 Don't create change at the dust limit, even if it means paying more than expected (Alex Morcos)

Tree-SHA512: d4cf939b97a92d63d4703ad152093c9dc60e74af590697bc21adbcdf17fc9e6ffb37d46d5eefafbd69327d1bcb79911f1b826ce1d960d895d464c4408c4995c3

src/qt/coincontroldialog.cpp

@@ -524,13 +524,10 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
                 CTxOut txout(nChange, (CScript)std::vector<unsigned char>(24, 0));
                 if (IsDust(txout, ::dustRelayFee))
                 {
-                    if (CoinControlDialog::fSubtractFeeFromAmount) // dust-change will be raised until no dust
+                    nPayFee += nChange;
-                        nChange = GetDustThreshold(txout, ::dustRelayFee);
+                    nChange = 0;
-                    else
+                    if (CoinControlDialog::fSubtractFeeFromAmount)
-                    {
+                        nBytes -= 34; // we didn't detect lack of change above
-                        nPayFee += nChange;
-                        nChange = 0;
-                    }
                 }
             }
 

src/wallet/wallet.cpp

@@ -2633,28 +2633,6 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT
 
                     CTxOut newTxOut(nChange, scriptChange);
 
-                    // We do not move dust-change to fees, because the sender would end up paying more than requested.
-                    // This would be against the purpose of the all-inclusive feature.
-                    // So instead we raise the change and deduct from the recipient.
-                    if (nSubtractFeeFromAmount > 0 && IsDust(newTxOut, ::dustRelayFee))
-                    {
-                        CAmount nDust = GetDustThreshold(newTxOut, ::dustRelayFee) - newTxOut.nValue;
-                        newTxOut.nValue += nDust; // raise change until no more dust
-                        for (unsigned int i = 0; i < vecSend.size(); i++) // subtract from first recipient
-                        {
-                            if (vecSend[i].fSubtractFeeFromAmount)
-                            {
-                                txNew.vout[i].nValue -= nDust;
-                                if (IsDust(txNew.vout[i], ::dustRelayFee))
-                                {
-                                    strFailReason = _("The transaction amount is too small to send after the fee has been deducted");
-                                    return false;
-                                }
-                                break;
-                            }
-                        }
-                    }
-
                     // Never create dust outputs; if we would, just
                     // add the dust to the fee.
                     if (IsDust(newTxOut, ::dustRelayFee))