simplify ChainstateManager::SnapshotBlockhash() return semantics

Don't return null snapshotblockhash values to avoid caller complexity/confusion.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/chain.h b/src/chain.h
index 43e8a39f36..04a5db5a17 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -163,14 +163,27 @@ public:
 
     //! Number of transactions in this block.
     //! Note: in a potential headers-first mode, this number cannot be relied upon
+    //! Note: this value is faked during UTXO snapshot load to ensure that
+    //! LoadBlockIndex() will load index entries for blocks that we lack data for.
+    //! @sa ActivateSnapshot
     unsigned int nTx{0};
 
     //! (memory only) Number of transactions in the chain up to and including this block.
     //! This value will be non-zero only if and only if transactions for this block and all its parents are available.
     //! Change to 64-bit type when necessary; won't happen before 2030
+    //!
+    //! Note: this value is faked during use of a UTXO snapshot because we don't
+    //! have the underlying block data available during snapshot load.
+    //! @sa AssumeutxoData
+    //! @sa ActivateSnapshot
     unsigned int nChainTx{0};
 
     //! Verification status of this block. See enum BlockStatus
+    //!
+    //! Note: this value is modified to show BLOCK_OPT_WITNESS during UTXO snapshot
+    //! load to avoid the block index being spuriously rewound.
+    //! @sa RewindBlockIndex
+    //! @sa ActivateSnapshot
     uint32_t nStatus{0};
 
     //! block header