Make last disconnected block BLOCK_FAILED_VALID, even when aborted

Author: sipa

src/validation.cpp

@@ -2829,25 +2829,30 @@ bool CChainState::InvalidateBlock(CValidationState& state, const CChainParams& c
         // and be left unable to start as they have no tip candidates (as there
         // are no blocks that meet the "have data and are not invalid per
         // nStatus" criteria for inclusion in setBlockIndexCandidates).
-        invalid_walk_tip->nStatus |= BLOCK_FAILED_CHILD;
+        invalid_walk_tip->nStatus |= BLOCK_FAILED_VALID;
         setDirtyBlockIndex.insert(invalid_walk_tip);
         setBlockIndexCandidates.erase(invalid_walk_tip);
         setBlockIndexCandidates.insert(invalid_walk_tip->pprev);
+        if (invalid_walk_tip->pprev == to_mark_failed && (to_mark_failed->nStatus & BLOCK_FAILED_VALID)) {
+            // We only want to mark the last disconnected block as BLOCK_FAILED_VALID; its children
+            // need to be BLOCK_FAILED_CHILD instead.
+            to_mark_failed->nStatus = (to_mark_failed->nStatus ^ BLOCK_FAILED_VALID) | BLOCK_FAILED_CHILD;
+            setDirtyBlockIndex.insert(to_mark_failed);
+        }
 
-        // If we abort invalidation after this iteration, make sure
-        // the last disconnected block gets marked failed (rather than
-        // just child of failed)
+        // Track the last disconnected block, so we can correct its BLOCK_FAILED_CHILD status in future
+        // iterations, or, if it's the last one, call InvalidChainFound on it.
         to_mark_failed = invalid_walk_tip;
     }
 
     {
-        // Mark pindex (or the last disconnected block) as invalid, regardless of whether it was in the main chain or not.
         LOCK(cs_main);
         if (chainActive.Contains(to_mark_failed)) {
             // If the to-be-marked invalid block is in the active chain, something is interfering and we can't proceed.
             return false;
         }
 
+        // Mark pindex (or the last disconnected block) as invalid, even when it never was in the main chain
         to_mark_failed->nStatus |= BLOCK_FAILED_VALID;
         setDirtyBlockIndex.insert(to_mark_failed);
         setBlockIndexCandidates.erase(to_mark_failed);