diff options
Diffstat (limited to 'src/coins.cpp')
| -rw-r--r-- | src/coins.cpp | 55 |
1 files changed, 33 insertions, 22 deletions
diff --git a/src/coins.cpp b/src/coins.cpp index b71362c6a0..6b4cb2aec7 100644 --- a/src/coins.cpp +++ b/src/coins.cpp @@ -77,8 +77,21 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi } if (!possible_overwrite) { if (!it->second.coin.IsSpent()) { - throw std::logic_error("Adding new coin that replaces non-pruned entry"); + throw std::logic_error("Attempted to overwrite an unspent coin (when possible_overwrite is false)"); } + // If the coin exists in this cache as a spent coin and is DIRTY, then + // its spentness hasn't been flushed to the parent cache. We're + // re-adding the coin to this cache now but we can't mark it as FRESH. + // If we mark it FRESH and then spend it before the cache is flushed + // we would remove it from this cache and would never flush spentness + // to the parent cache. + // + // Re-adding a spent coin can happen in the case of a re-org (the coin + // is 'spent' when the block adding it is disconnected and then + // re-added when it is also added in a newly connected block). + // + // If the coin doesn't exist in the current cache, or is spent but not + // DIRTY, then it can be marked FRESH. fresh = !(it->second.flags & CCoinsCacheEntry::DIRTY); } it->second.coin = std::move(coin); @@ -86,12 +99,12 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi cachedCoinsUsage += it->second.coin.DynamicMemoryUsage(); } -void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool check) { +void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool check_for_overwrite) { bool fCoinbase = tx.IsCoinBase(); const uint256& txid = tx.GetHash(); for (size_t i = 0; i < tx.vout.size(); ++i) { - bool overwrite = check ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase; - // Always set the possible_overwrite flag to AddCoin for coinbase txn, in order to correctly + bool overwrite = check_for_overwrite ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase; + // Coinbase transactions can always be overwritten, in order to correctly // deal with the pre-BIP30 occurrences of duplicate coinbase transactions. cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase), overwrite); } @@ -152,11 +165,11 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn } CCoinsMap::iterator itUs = cacheCoins.find(it->first); if (itUs == cacheCoins.end()) { - // The parent cache does not have an entry, while the child does - // We can ignore it if it's both FRESH and pruned in the child + // The parent cache does not have an entry, while the child cache does. + // We can ignore it if it's both spent and FRESH in the child if (!(it->second.flags & CCoinsCacheEntry::FRESH && it->second.coin.IsSpent())) { - // Otherwise we will need to create it in the parent - // and move the data up and mark it as dirty + // Create the coin in the parent cache, move the data up + // and mark it as dirty. CCoinsCacheEntry& entry = cacheCoins[it->first]; entry.coin = std::move(it->second.coin); cachedCoinsUsage += entry.coin.DynamicMemoryUsage(); @@ -169,19 +182,18 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn } } } else { - // Assert that the child cache entry was not marked FRESH if the - // parent cache entry has unspent outputs. If this ever happens, - // it means the FRESH flag was misapplied and there is a logic - // error in the calling code. + // Found the entry in the parent cache if ((it->second.flags & CCoinsCacheEntry::FRESH) && !itUs->second.coin.IsSpent()) { - throw std::logic_error("FRESH flag misapplied to cache entry for base transaction with spendable outputs"); + // The coin was marked FRESH in the child cache, but the coin + // exists in the parent cache. If this ever happens, it means + // the FRESH flag was misapplied and there is a logic error in + // the calling code. + throw std::logic_error("FRESH flag misapplied to coin that exists in parent cache"); } - // Found the entry in the parent cache if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coin.IsSpent()) { - // The grandparent does not have an entry, and the child is - // modified and being pruned. This means we can just delete - // it from the parent. + // The grandparent cache does not have an entry, and the coin + // has been spent. We can just delete it from the parent cache. cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage(); cacheCoins.erase(itUs); } else { @@ -190,11 +202,10 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn itUs->second.coin = std::move(it->second.coin); cachedCoinsUsage += itUs->second.coin.DynamicMemoryUsage(); itUs->second.flags |= CCoinsCacheEntry::DIRTY; - // NOTE: It is possible the child has a FRESH flag here in - // the event the entry we found in the parent is pruned. But - // we must not copy that FRESH flag to the parent as that - // pruned state likely still needs to be communicated to the - // grandparent. + // NOTE: It isn't safe to mark the coin as FRESH in the parent + // cache. If it already existed and was spent in the parent + // cache then marking it FRESH would prevent that spentness + // from being flushed to the grandparent. } } } |