Method ActivateBestChainStep

src/validation.cpp:3201–3284

* Try to make some progress towards making index_most_work the active block. * pblock is either nullptr or a pointer to a CBlock corresponding to index_most_work. * * @returns true unless a system error occurred */

 * @returns true unless a system error occurred
 */
bool Chainstate::ActivateBestChainStep(BlockValidationState& state, CBlockIndex& index_most_work, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, std::vector<ConnectedBlock>& connected_blocks)
{
    AssertLockHeld(cs_main);
    if (m_mempool) AssertLockHeld(m_mempool->cs);

    const CBlockIndex* pindexOldTip = m_chain.Tip();
    const CBlockIndex* pindexFork = m_chain.FindFork(index_most_work);

    // Disconnect active blocks which are no longer in the best chain.
    bool fBlocksDisconnected = false;
    DisconnectedBlockTransactions disconnectpool{MAX_DISCONNECTED_TX_POOL_BYTES};
    while (m_chain.Tip() && m_chain.Tip() != pindexFork) {
        if (!DisconnectTip(state, &disconnectpool)) {
            // This is likely a fatal error, but keep the mempool consistent,
            // just in case. Only remove from the mempool in this case.
            MaybeUpdateMempoolForReorg(disconnectpool, false);

            // If we're unable to disconnect a block during normal operation,
            // then that is a failure of our local system -- we should abort
            // rather than stay on a less work chain.
            FatalError(m_chainman.GetNotifications(), state, _("Failed to disconnect block."));
            return false;
        }
        fBlocksDisconnected = true;
    }

    // Build list of new blocks to connect (in descending height order).
    std::vector<CBlockIndex*> vpindexToConnect;
    bool fContinue = true;
    int nHeight = pindexFork ? pindexFork->nHeight : -1;
    while (fContinue && nHeight != index_most_work.nHeight) {
        // Don't iterate the entire list of potential improvements toward the best tip, as we likely only need
        // a few blocks along the way.
        int nTargetHeight = std::min(nHeight + 32, index_most_work.nHeight);
        vpindexToConnect.clear();
        vpindexToConnect.reserve(nTargetHeight - nHeight);
        CBlockIndex* pindexIter = index_most_work.GetAncestor(nTargetHeight);
        while (pindexIter && pindexIter->nHeight != nHeight) {
            vpindexToConnect.push_back(pindexIter);
            pindexIter = pindexIter->pprev;
        }
        nHeight = nTargetHeight;

        // Connect new blocks.
        for (CBlockIndex* pindexConnect : vpindexToConnect | std::views::reverse) {
            if (!ConnectTip(state, pindexConnect, pindexConnect == &index_most_work ? pblock : std::shared_ptr<const CBlock>(), connected_blocks, disconnectpool)) {
                if (state.IsInvalid()) {
                    // The block violates a consensus rule.
                    if (state.GetResult() != BlockValidationResult::BLOCK_MUTATED) {
                        InvalidChainFound(vpindexToConnect.front());
                    }
                    state = BlockValidationState();
                    fInvalidFound = true;
                    fContinue = false;
                    break;
                } else {
                    // A system error occurred (disk space, database error, ...).
                    // Make the mempool consistent with the current tip, just in case