Repository: bitcoin/bitcoin
File: src/node/miner.cpp (C++)

Code before:
    pblock->nVersion = m_chainstate.m_chainman.m_versionbitscache.ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
    // -regtest only: allow overriding block.nVersion with
    // -blockversion=N to test forking scenarios
    if (chainparams.MineBlocksOnDemand()) {
        pblock->nVersion = gArgs.GetIntArg("-blockversion", pblock->nVersion);
    }

    pblock->nTime = TicksSinceEpoch<std::chrono::seconds>(NodeClock::now());
    m_lock_time_cutoff = pindexPrev->GetMedianTimePast();

    int nPackagesSelected = 0;
    int nDescendantsUpdated = 0;
    if (m_mempool) {
        addPackageTxs(nPackagesSelected, nDescendantsUpdated);
    }

    const auto time_1{SteadyClock::now()};

    m_last_block_num_txs = nBlockTx;
    m_last_block_weight = nBlockWeight;

    // Create coinbase transaction.
    CMutableTransaction coinbaseTx;
    coinbaseTx.vin.resize(1);
    coinbaseTx.vin[0].prevout.SetNull();
    coinbaseTx.vout.resize(1);
    coinbaseTx.vout[0].scriptPubKey = m_options.coinbase_output_script;
    coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
    coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
    pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
    pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);

    LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);

    // Fill in header
    pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
    UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
    pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
    pblock->nNonce         = 0;

    BlockValidationState state;
    if (m_options.test_block_validity && !TestBlockValidity(state, chainparams, m_chainstate, *pblock, pindexPrev,
                                                            /*fCheckPOW=*/false, /*fCheckMerkleRoot=*/false)) {
        throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, state.ToString()));
    }
    const auto time_2{SteadyClock::now()};

    LogDebug(BCLog::BENCH, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n",
             Ticks<MillisecondsDouble>(time_1 - time_start), nPackagesSelected, nDescendantsUpdated,
             Ticks<MillisecondsDouble>(time_2 - time_1),
             Ticks<MillisecondsDouble>(time_2 - time_start));

Review comment (refactor):
2c10f93d0bd920f20e91f1be7c82e66af2a52919 nit: can you move this down next to `nLockTime`? This line is what makes the `nLockTime` bit work, so makes sense to have them together. Also, in https://github.com/Sjors/bitcoin/pull/49 I put this behavior behind a startup flag.

Code after:
    pblock->nVersion = m_chainstate.m_chainman.m_versionbitscache.ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
    // -regtest only: allow overriding block.nVersion with
    // -blockversion=N to test forking scenarios
    if (chainparams.MineBlocksOnDemand()) {
        pblock->nVersion = gArgs.GetIntArg("-blockversion", pblock->nVersion);
    }

    pblock->nTime = TicksSinceEpoch<std::chrono::seconds>(NodeClock::now());
    m_lock_time_cutoff = pindexPrev->GetMedianTimePast();

    int nPackagesSelected = 0;
    int nDescendantsUpdated = 0;
    if (m_mempool) {
        addPackageTxs(nPackagesSelected, nDescendantsUpdated);
    }

    const auto time_1{SteadyClock::now()};

    m_last_block_num_txs = nBlockTx;
    m_last_block_weight = nBlockWeight;

    // Create coinbase transaction.
    CMutableTransaction coinbaseTx;
    coinbaseTx.vin.resize(1);
    coinbaseTx.vin[0].prevout.SetNull();
    coinbaseTx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL; // Make sure timelock is enforced.
    coinbaseTx.vout.resize(1);
    coinbaseTx.vout[0].scriptPubKey = m_options.coinbase_output_script;
    coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
    coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
    Assert(nHeight > 0);
    coinbaseTx.nLockTime = static_cast<uint32_t>(nHeight - 1);
    pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
    pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);

    LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);

    // Fill in header
    pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
    UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
    pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
    pblock->nNonce         = 0;

    BlockValidationState state;
    if (m_options.test_block_validity && !TestBlockValidity(state, chainparams, m_chainstate, *pblock, pindexPrev,
                                                            /*fCheckPOW=*/false, /*fCheckMerkleRoot=*/false)) {
        throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, state.ToString()));
    }
    const auto time_2{SteadyClock::now()};

    LogDebug(BCLog::BENCH, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n",