add asserts in CheckBlockIndex, fix SetBlockFailureFlags

- also modify block_index_tree.cpp to add blocks

Author: stratospher

src/test/fuzz/block_index_tree.cpp

@@ -39,6 +39,7 @@ void initialize_block_index_tree()
 FUZZ_TARGET(block_index_tree, .init = initialize_block_index_tree)
 {
     FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    SetMockTime(ConsumeTime(fuzzed_data_provider));
     ChainstateManager& chainman = *g_setup->m_node.chainman;
     auto& blockman = chainman.m_blockman;
     CBlockIndex* genesis = chainman.ActiveChainstate().m_chain[0];
@@ -58,6 +59,7 @@ FUZZ_TARGET(block_index_tree, .init = initialize_block_index_tree)
                     CBlockHeader header = ConsumeBlockHeader(fuzzed_data_provider, prev_block->GetBlockHash(), nonce_counter);
                     CBlockIndex* index = blockman.AddToBlockIndex(header, chainman.m_best_header);
                     assert(index->nStatus & BLOCK_VALID_TREE);
+                    blocks.push_back(index);
                 }
             },
             [&] {

src/validation.cpp

@@ -3826,8 +3826,8 @@ void Chainstate::SetBlockFailureFlags(CBlockIndex* invalid_block)
     AssertLockHeld(cs_main);
 
     for (auto& [_, block_index] : m_blockman.m_block_index) {
-        if (block_index.GetAncestor(invalid_block->nHeight) == invalid_block && !(block_index.nStatus & BLOCK_FAILED_MASK)) {
-            block_index.nStatus |= BLOCK_FAILED_CHILD;
+        if (&block_index != invalid_block && block_index.GetAncestor(invalid_block->nHeight) == invalid_block) {
+            block_index.nStatus = (block_index.nStatus & ~BLOCK_FAILED_VALID) | BLOCK_FAILED_CHILD;
         }
     }
 }
@@ -5400,6 +5400,14 @@ void ChainstateManager::CheckBlockIndex()
             // Checks for not-invalid blocks.
             assert((pindex->nStatus & BLOCK_FAILED_MASK) == 0); // The failed mask cannot be set for blocks without invalid parents.
         }
+        else if (pindexFirstInvalid != pindex) {
+            // pindexFirstInvalid -> ...... -> pindex
+            // we check that descendants are BLOCK_FAILED_CHILD and not BLOCK_FAILED_VALID
+            assert((pindex->nStatus & BLOCK_FAILED_VALID) == 0);
+            assert(pindex->nStatus & BLOCK_FAILED_CHILD);
+        } else {
+            assert(pindex->nStatus & BLOCK_FAILED_VALID);
+        }
         // Make sure m_chain_tx_count sum is correctly computed.
         if (!pindex->pprev) {
             // If no previous block, nTx and m_chain_tx_count must be the same.