1 files changed, 44 insertions, 1 deletions

diff --git a/src/main.h b/src/main.h
index 8bb536b..382dd9c 100644
--- a/src/main.h
+++ b/src/main.h
@@ -342,9 +342,52 @@ struct WalletRecoveryAudit
     }
 };
 WalletRecoveryAudit GetWalletRecoveryAudit();
-bool CreateTransaction(CScript scriptPubKey, int64 nValue, CWalletTx& txNew, int64& nFeeRequiredRet);
+
+// Why a send did not go through.
+//
+// The pool's payout thread has to decide, on every failed SendMoney, whether
+// the failure was the wallet's condition (wait for it to change) or a fault
+// (something is wrong with this payment). It used to guess by re-reading
+// GetBalance() afterwards and allowing a fixed CENT of headroom for the fee.
+// That cannot work: the fee here is a step function of the SERIALISED SIZE of
+// a transaction that no longer exists, and the step is from 0 to 11 * CENT at
+// 10,000 bytes -- so a one-CENT allowance is either unnecessary or an order of
+// magnitude short, never right. A pool wallet close to broke selects many
+// small inputs BECAUSE it is close to broke, which is what pushes the
+// transaction over 10 KB, so the guess is wrong exactly when the money is
+// tight.
+//
+// The wallet already knows the answer; it just did not say. SelectCoins()
+// failing is "there is not enough spendable coin to cover the amount plus
+// whatever fee this size of transaction requires", and it is the only reason
+// CreateTransaction() can fail that is about funding rather than about the
+// wallet being broken.
+enum WalletSendResult
+{
+    WALLET_SEND_OK = 0,
+    WALLET_SEND_INSUFFICIENT_FUNDS, // coin selection could not cover amount+fee
+    WALLET_SEND_FAILED              // anything else: could not build, sign or accept
+};
+
+// What the wallet did with a send request. nFeeRequired is the fee the
+// transaction turned out to need, which for a failed send is what coin
+// selection was asked for on top of the amount and could not find -- 0 if it
+// never got that far.
+struct SendMoneyOutcome
+{
+    WalletSendResult result       = WALLET_SEND_OK;
+    int64            nFeeRequired = 0;
+};
+
+bool CreateTransaction(CScript scriptPubKey, int64 nValue, CWalletTx& txNew, int64& nFeeRequiredRet,
+                       WalletSendResult* presultRet=NULL);
 bool CommitTransactionSpent(const CWalletTx& wtxNew);
+// The three-argument form is kept, and kept as a distinct declaration rather
+// than a defaulted argument, because gui.cpp declares SendMoney itself instead
+// of including this header.
 bool SendMoney(CScript scriptPubKey, int64 nValue, CWalletTx& wtxNew);
+bool SendMoney(CScript scriptPubKey, int64 nValue, CWalletTx& wtxNew,
+               SendMoneyOutcome& outcomeRet);