refactor: Avoid magic value of all-zeros in assumeutxo base_blockhash

Just use std::optional

src/test/validation_chainstatemanager_tests.cpp

@@ -226,10 +226,8 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup)
 
     // Snapshot should refuse to load at this height.
     BOOST_REQUIRE(!CreateAndActivateUTXOSnapshot(m_node, m_path_root));
-    BOOST_CHECK(chainman.ActiveChainstate().m_from_snapshot_blockhash.IsNull());
-    BOOST_CHECK_EQUAL(
-        chainman.ActiveChainstate().m_from_snapshot_blockhash,
-        chainman.SnapshotBlockhash().value_or(uint256()));
+    BOOST_CHECK(!chainman.ActiveChainstate().m_from_snapshot_blockhash);
+    BOOST_CHECK(!chainman.SnapshotBlockhash());
 
     // Mine 10 more blocks, putting at us height 110 where a valid assumeutxo value can
     // be found.
@@ -274,9 +272,9 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup)
     BOOST_REQUIRE(CreateAndActivateUTXOSnapshot(m_node, m_path_root));
 
     // Ensure our active chain is the snapshot chainstate.
-    BOOST_CHECK(!chainman.ActiveChainstate().m_from_snapshot_blockhash.IsNull());
+    BOOST_CHECK(!chainman.ActiveChainstate().m_from_snapshot_blockhash->IsNull());
     BOOST_CHECK_EQUAL(
-        chainman.ActiveChainstate().m_from_snapshot_blockhash,
+        *chainman.ActiveChainstate().m_from_snapshot_blockhash,
         *chainman.SnapshotBlockhash());
 
     const AssumeutxoData& au_data = *ExpectedAssumeutxo(snapshot_height, ::Params());
@@ -352,7 +350,7 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup)
 
     // Snapshot blockhash should be unchanged.
     BOOST_CHECK_EQUAL(
-        chainman.ActiveChainstate().m_from_snapshot_blockhash,
+        *chainman.ActiveChainstate().m_from_snapshot_blockhash,
         loaded_snapshot_blockhash);
 }
 

src/validation.cpp

@@ -1158,7 +1158,7 @@ void CoinsViews::InitCache()
     m_cacheview = std::make_unique<CCoinsViewCache>(&m_catcherview);
 }
 
-CChainState::CChainState(CTxMemPool& mempool, BlockManager& blockman, uint256 from_snapshot_blockhash)
+CChainState::CChainState(CTxMemPool& mempool, BlockManager& blockman, std::optional<uint256> from_snapshot_blockhash)
     : m_mempool(mempool),
       m_blockman(blockman),
       m_from_snapshot_blockhash(from_snapshot_blockhash) {}
@@ -1169,8 +1169,8 @@ void CChainState::InitCoinsDB(
     bool should_wipe,
     std::string leveldb_name)
 {
-    if (!m_from_snapshot_blockhash.IsNull()) {
-        leveldb_name += "_" + m_from_snapshot_blockhash.ToString();
+    if (m_from_snapshot_blockhash) {
+        leveldb_name += "_" + m_from_snapshot_blockhash->ToString();
     }
 
     m_coins_views = std::make_unique<CoinsViews>(
@@ -3877,7 +3877,7 @@ bool CVerifyDB::VerifyDB(
     int reportDone = 0;
     LogPrintf("[0%%]..."); /* Continued */
 
-    bool is_snapshot_cs = !chainstate.m_from_snapshot_blockhash.IsNull();
+    const bool is_snapshot_cs{!chainstate.m_from_snapshot_blockhash};
 
     for (pindex = chainstate.m_chain.Tip(); pindex && pindex->pprev; pindex = pindex->pprev) {
         const int percentageDone = std::max(1, std::min(99, (int)(((double)(chainstate.m_chain.Height() - pindex->nHeight)) / (double)nCheckDepth * (nCheckLevel >= 4 ? 50 : 100))));
@@ -4458,8 +4458,8 @@ std::string CChainState::ToString()
 {
     CBlockIndex* tip = m_chain.Tip();
     return strprintf("Chainstate [%s] @ height %d (%s)",
-        m_from_snapshot_blockhash.IsNull() ? "ibd" : "snapshot",
-        tip ? tip->nHeight : -1, tip ? tip->GetBlockHash().ToString() : "null");
+                     m_from_snapshot_blockhash ? "snapshot" : "ibd",
+                     tip ? tip->nHeight : -1, tip ? tip->GetBlockHash().ToString() : "null");
 }
 
 bool CChainState::ResizeCoinsCaches(size_t coinstip_size, size_t coinsdb_size)
@@ -4662,10 +4662,10 @@ double GuessVerificationProgress(const ChainTxData& data, const CBlockIndex *pin
     return std::min<double>(pindex->nChainTx / fTxTotal, 1.0);
 }
 
-std::optional<uint256> ChainstateManager::SnapshotBlockhash() const {
+std::optional<uint256> ChainstateManager::SnapshotBlockhash() const
+{
     LOCK(::cs_main);
-    if (m_active_chainstate != nullptr &&
-            !m_active_chainstate->m_from_snapshot_blockhash.IsNull()) {
+    if (m_active_chainstate && m_active_chainstate->m_from_snapshot_blockhash) {
         // If a snapshot chainstate exists, it will always be our active.
         return m_active_chainstate->m_from_snapshot_blockhash;
     }
@@ -4688,9 +4688,9 @@ std::vector<CChainState*> ChainstateManager::GetAll()
     return out;
 }
 
-CChainState& ChainstateManager::InitializeChainstate(CTxMemPool& mempool, const uint256& snapshot_blockhash)
+CChainState& ChainstateManager::InitializeChainstate(CTxMemPool& mempool, const std::optional<uint256>& snapshot_blockhash)
 {
-    bool is_snapshot = !snapshot_blockhash.IsNull();
+    bool is_snapshot = snapshot_blockhash.has_value();
     std::unique_ptr<CChainState>& to_modify =
         is_snapshot ? m_snapshot_chainstate : m_ibd_chainstate;
 

src/validation.h

@@ -553,7 +553,7 @@ class CChainState
     //! CChainState instances.
     BlockManager& m_blockman;
 
-    explicit CChainState(CTxMemPool& mempool, BlockManager& blockman, uint256 from_snapshot_blockhash = uint256());
+    explicit CChainState(CTxMemPool& mempool, BlockManager& blockman, std::optional<uint256> from_snapshot_blockhash = std::nullopt);
 
     /**
      * Initialize the CoinsViews UTXO set database management data structures. The in-memory
@@ -584,9 +584,9 @@ class CChainState
     /**
      * The blockhash which is the base of the snapshot this chainstate was created from.
      *
-     * IsNull() if this chainstate was not created from a snapshot.
+     * std::nullopt if this chainstate was not created from a snapshot.
      */
-    const uint256 m_from_snapshot_blockhash{};
+    const std::optional<uint256> m_from_snapshot_blockhash;
 
     /**
      * The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS (for itself and all ancestors) and
@@ -866,7 +866,7 @@ class ChainstateManager
     //                                  constructor
     //! @param[in] snapshot_blockhash   If given, signify that this chainstate
     //!                                 is based on a snapshot.
-    CChainState& InitializeChainstate(CTxMemPool& mempool, const uint256& snapshot_blockhash = uint256())
+    CChainState& InitializeChainstate(CTxMemPool& mempool, const std::optional<uint256>& snapshot_blockhash = std::nullopt)
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
     //! Get all chainstates currently being used.