Merge bitcoin/bitcoin#24050: validation: Give `m_block_index` ownership of `CBlockIndex`s

6c23c415613d8b847e6f6a2f872be893da9f4384 refactor: Rewrite AddToBlockIndex with try_emplace (Carl Dong)
c05cf7aa1e1c15089753897a10c14762027d4b99 style: Modernize range-based loops over m_block_index (Carl Dong)
c2a1655799c5d5dab9b14bd2a6b2d2296efd6964 style-only: Use using instead of typedef for BlockMap (Carl Dong)
dd79dad17545424d145e846026518d70da594380 refactor: Rewrite InsertBlockIndex with try_emplace (Carl Dong)
531dce034718523967808a89c18ba69a1e3e5a1f tests: Remove now-unnecessary manual Unload's (Carl Dong)
bec86ae32683ac56b4e6ba9c9b7d21cfbdf4ac03 blockstorage: Make m_block_index own CBlockIndex's (Carl Dong)

Pull request description:

  Part of: #24303
  Split off from: #22564

  ```
  Instead of having CBlockIndex's live on the heap, which requires manual
  memory management, have them be owned by m_block_index. This means that
  they will live and die with BlockManager.
  ```

  The second commit demonstrates how this makes calls to `Unload()` to satisfy the address sanitizer unnecessary.

ACKs for top commit:
  ajtowns:
    ACK 6c23c415613d8b847e6f6a2f872be893da9f4384
  MarcoFalke:
    re-ACK 6c23c415613d8b847e6f6a2f872be893da9f4384 🎨

Tree-SHA512: 81b2b5119be27cc0f8a9457b11da60cc60930315d2a5be36be89fe253d32073ffe622348ff153114b9b3212197bddbc791810913a43811b33cc58e7162bd105b

1 files changed, 20 insertions, 24 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index c89c293a85..d80e2576d2 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1978,7 +1978,7 @@ bool CChainState::ConnectBlock(const CBlock& block, BlockValidationState& state,
         //  effectively caching the result of part of the verification.
         BlockMap::const_iterator  it = m_blockman.m_block_index.find(hashAssumeValid);
         if (it != m_blockman.m_block_index.end()) {
-            if (it->second->GetAncestor(pindex->nHeight) == pindex &&
+            if (it->second.GetAncestor(pindex->nHeight) == pindex &&
                 pindexBestHeader->GetAncestor(pindex->nHeight) == pindex &&
                 pindexBestHeader->nChainWork >= nMinimumChainWork) {
                 // This block is a member of the assumed verified chain and an ancestor of the best header.
@@ -3035,8 +3035,8 @@ bool CChainState::InvalidateBlock(BlockValidationState& state, CBlockIndex* pind
 
     {
         LOCK(cs_main);
-        for (const auto& entry : m_blockman.m_block_index) {
-            CBlockIndex *candidate = entry.second;
+        for (auto& entry : m_blockman.m_block_index) {
+            CBlockIndex* candidate = &entry.second;
             // We don't need to put anything in our active chain into the
             // multimap, because those candidates will be found and considered
             // as we disconnect.
@@ -3133,12 +3133,10 @@ bool CChainState::InvalidateBlock(BlockValidationState& state, CBlockIndex* pind
         // it up here, this should be an essentially unobservable error.
         // Loop back over all block index entries and add any missing entries
         // to setBlockIndexCandidates.
-        BlockMap::iterator it = m_blockman.m_block_index.begin();
-        while (it != m_blockman.m_block_index.end()) {
-            if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->HaveTxsDownloaded() && !setBlockIndexCandidates.value_comp()(it->second, m_chain.Tip())) {
-                setBlockIndexCandidates.insert(it->second);
+        for (auto& [_, block_index] : m_blockman.m_block_index) {
+            if (block_index.IsValid(BLOCK_VALID_TRANSACTIONS) && block_index.HaveTxsDownloaded() && !setBlockIndexCandidates.value_comp()(&block_index, m_chain.Tip())) {
+                setBlockIndexCandidates.insert(&block_index);
             }
-            it++;
         }
 
         InvalidChainFound(to_mark_failed);
@@ -3157,21 +3155,19 @@ void CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
     int nHeight = pindex->nHeight;
 
     // Remove the invalidity flag from this block and all its descendants.
-    BlockMap::iterator it = m_blockman.m_block_index.begin();
-    while (it != m_blockman.m_block_index.end()) {
-        if (!it->second->IsValid() && it->second->GetAncestor(nHeight) == pindex) {
-            it->second->nStatus &= ~BLOCK_FAILED_MASK;
-            m_blockman.m_dirty_blockindex.insert(it->second);
-            if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->HaveTxsDownloaded() && setBlockIndexCandidates.value_comp()(m_chain.Tip(), it->second)) {
-                setBlockIndexCandidates.insert(it->second);
+    for (auto& [_, block_index] : m_blockman.m_block_index) {
+        if (!block_index.IsValid() && block_index.GetAncestor(nHeight) == pindex) {
+            block_index.nStatus &= ~BLOCK_FAILED_MASK;
+            m_blockman.m_dirty_blockindex.insert(&block_index);
+            if (block_index.IsValid(BLOCK_VALID_TRANSACTIONS) && block_index.HaveTxsDownloaded() && setBlockIndexCandidates.value_comp()(m_chain.Tip(), &block_index)) {
+                setBlockIndexCandidates.insert(&block_index);
             }
-            if (it->second == m_chainman.m_best_invalid) {
+            if (&block_index == m_chainman.m_best_invalid) {
                 // Reset invalid block marker if it was pointing to one of those.
                 m_chainman.m_best_invalid = nullptr;
             }
-            m_chainman.m_failed_blocks.erase(it->second);
+            m_chainman.m_failed_blocks.erase(&block_index);
         }
-        it++;
     }
 
     // Remove the invalidity flag from all ancestors too.
@@ -3500,7 +3496,7 @@ bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValida
     if (hash != chainparams.GetConsensus().hashGenesisBlock) {
         if (miSelf != m_blockman.m_block_index.end()) {
             // Block header is already known.
-            CBlockIndex* pindex = miSelf->second;
+            CBlockIndex* pindex = &(miSelf->second);
             if (ppindex)
                 *ppindex = pindex;
             if (pindex->nStatus & BLOCK_FAILED_MASK) {
@@ -3522,7 +3518,7 @@ bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValida
             LogPrint(BCLog::VALIDATION, "%s: %s prev block not found\n", __func__, hash.ToString());
             return state.Invalid(BlockValidationResult::BLOCK_MISSING_PREV, "prev-blk-not-found");
         }
-        pindexPrev = (*mi).second;
+        pindexPrev = &((*mi).second);
         if (pindexPrev->nStatus & BLOCK_FAILED_MASK) {
             LogPrint(BCLog::VALIDATION, "%s: %s prev block invalid\n", __func__, hash.ToString());
             return state.Invalid(BlockValidationResult::BLOCK_INVALID_PREV, "bad-prevblk");
@@ -3994,13 +3990,13 @@ bool CChainState::ReplayBlocks()
     if (m_blockman.m_block_index.count(hashHeads[0]) == 0) {
         return error("ReplayBlocks(): reorganization to unknown block requested");
     }
-    pindexNew = m_blockman.m_block_index[hashHeads[0]];
+    pindexNew = &(m_blockman.m_block_index[hashHeads[0]]);
 
     if (!hashHeads[1].IsNull()) { // The old tip is allowed to be 0, indicating it's the first flush.
         if (m_blockman.m_block_index.count(hashHeads[1]) == 0) {
             return error("ReplayBlocks(): reorganization from unknown block requested");
         }
-        pindexOld = m_blockman.m_block_index[hashHeads[1]];
+        pindexOld = &(m_blockman.m_block_index[hashHeads[1]]);
         pindexFork = LastCommonAncestor(pindexOld, pindexNew);
         assert(pindexFork != nullptr);
     }
@@ -4267,8 +4263,8 @@ void CChainState::CheckBlockIndex()
 
     // Build forward-pointing map of the entire block tree.
     std::multimap<CBlockIndex*,CBlockIndex*> forward;
-    for (const std::pair<const uint256, CBlockIndex*>& entry : m_blockman.m_block_index) {
-        forward.insert(std::make_pair(entry.second->pprev, entry.second));
+    for (auto& [_, block_index] : m_blockman.m_block_index) {
+        forward.emplace(block_index.pprev, &block_index);
     }
 
     assert(forward.size() == m_blockman.m_block_index.size());