Bugfix: the end of a reorged chain is invalid when connect fails

sipa · furszy · commit b7910a8d7d46 · 2021-04-24T12:02:05.000-03:00
Introduced in 4e0eed8 When an invalid block is found during a reorg, we know the last of the blocks in the was-to-be-connected chain is invalid, but not necessarily the first. As vpIndexToConnect is ordered in decreasing height, the end of the reorg is the front of the vector, and not the back. This only affected the warning system.
diff --git a/src/validation.cpp b/src/validation.cpp
@@ -2287,8 +2287,9 @@ static bool ActivateBestChainStep(CValidationState& state, CBlockIndex* pindexMo
             if (!ConnectTip(state, pindexConnect, (pindexConnect == pindexMostWork) ? pblock : std::shared_ptr<const CBlock>(), connectTrace, disconnectpool)) {
                 if (state.IsInvalid()) {
                     // The block violates a consensus rule.
-                    if (!state.CorruptionPossible())
-                        InvalidChainFound(vpindexToConnect.back());
+                    if (!state.CorruptionPossible()) {
+                        InvalidChainFound(vpindexToConnect.front());
+                    }
                     state = CValidationState();
                     fInvalidFound = true;
                     fContinue = false;
