Repository: bitcoin/bitcoin
File: src/index/coinstatsindex.cpp (C++)

Code before:
    m_total_subsidy += block_subsidy;

    // Ignore genesis block
    if (block.height > 0) {
        std::pair<uint256, DBVal> read_out;
        if (!m_db->Read(DBHeightKey(block.height - 1), read_out)) {
            return false;
        }

        uint256 expected_block_hash{*Assert(block.prev_hash)};
        if (read_out.first != expected_block_hash) {
            LogWarning("previous block header belongs to unexpected block %s; expected %s",
                      read_out.first.ToString(), expected_block_hash.ToString());

            if (!m_db->Read(DBHashKey(expected_block_hash), read_out)) {
                LogError("previous block header not found; expected %s",
                          expected_block_hash.ToString());
                return false;
            }
        }

        // Add the new utxos created from the block
        assert(block.data);
        for (size_t i = 0; i < block.data->vtx.size(); ++i) {
            const auto& tx{block.data->vtx.at(i)};

            // Skip duplicate txid coinbase transactions (BIP30).
            if (IsBIP30Unspendable(block.hash, block.height) && tx->IsCoinBase()) {
                m_total_unspendable_amount += block_subsidy;
                m_total_unspendables_bip30 += block_subsidy;
                continue;
            }

            for (uint32_t j = 0; j < tx->vout.size(); ++j) {
                const CTxOut& out{tx->vout[j]};
                Coin coin{out, block.height, tx->IsCoinBase()};
                COutPoint outpoint{tx->GetHash(), j};

                // Skip unspendable coins
                if (coin.out.scriptPubKey.IsUnspendable()) {
                    m_total_unspendable_amount += coin.out.nValue;
                    m_total_unspendables_scripts += coin.out.nValue;
                    continue;
                }

                ApplyCoinHash(m_muhash, outpoint, coin);

                if (tx->IsCoinBase()) {
                    m_total_coinbase_amount += coin.out.nValue;
                } else {
                    m_total_new_outputs_ex_coinbase_amount += coin.out.nValue;

Review comment (bug):
Shouldn't this be an error even if you can find the previous block header? You'll calculate incorrect values for `total_amount` otherwise?

Code after:
    // a bug and is superseded by a fixed version at "indexes/coinstatsindex".
    // The original index is kept around until the next release in case users
    // decide to downgrade their node.
    auto old_path = gArgs.GetDataDirNet() / "indexes" / "coinstats";
    if (fs::exists(old_path)) {
        // TODO: Change this to deleting the old index with v31.
        LogWarning("Old version of coinstatsindex found at %s. This folder can be safely deleted unless you " \
            "plan to downgrade your node to version 29 or lower.", fs::PathToString(old_path));
    }
    fs::path path{gArgs.GetDataDirNet() / "indexes" / "coinstatsindex"};
    fs::create_directories(path);

    m_db = std::make_unique<CoinStatsIndex::DB>(path / "db", n_cache_size, f_memory, f_wipe);
}

bool CoinStatsIndex::CustomAppend(const interfaces::BlockInfo& block)
{
    const CAmount block_subsidy{GetBlockSubsidy(block.height, Params().GetConsensus())};
    m_total_subsidy += block_subsidy;

    // Ignore genesis block
    if (block.height > 0) {
        uint256 expected_block_hash{*Assert(block.prev_hash)};
        if (m_current_block_hash != expected_block_hash) {
            LogError("previous block header belongs to unexpected block %s; expected %s",
                      m_current_block_hash.ToString(), expected_block_hash.ToString());
            return false;
        }

        // Add the new utxos created from the block
        assert(block.data);
        for (size_t i = 0; i < block.data->vtx.size(); ++i) {
            const auto& tx{block.data->vtx.at(i)};
            const bool is_coinbase{tx->IsCoinBase()};

            // Skip duplicate txid coinbase transactions (BIP30).
            if (is_coinbase && IsBIP30Unspendable(block.hash, block.height)) {
                m_total_unspendables_bip30 += block_subsidy;
                continue;
            }

            for (uint32_t j = 0; j < tx->vout.size(); ++j) {
                const CTxOut& out{tx->vout[j]};
                const Coin coin{out, block.height, is_coinbase};
                const COutPoint outpoint{tx->GetHash(), j};

                // Skip unspendable coins
                if (coin.out.scriptPubKey.IsUnspendable()) {
                    m_total_unspendables_scripts += coin.out.nValue;
                    continue;
                }