Merge #19069: refactor: replace pointers by references within tx_verify.{h,cpp}

b00266f refactor: replace pointers by references within tx_verify.{h,cpp} (Sebastian Falbesoner)

Pull request description:

  This PR gets rid of another unnecessary use of raw pointers, similar to PR #19053 (see also issue #19062 where useful commands for finding potential candidates are listed) but in the tx verification module.

  For the functions `CalculateSequenceLocks()` and `SequenceLocks()`, the  `prevHeights` vector parameter type is changed to be passed as a reference. Note that there were no checks for null pointers -- if one would pass `nullptr` to one of the functions, the following line would immediately lead to a crash:
  https://github.com/bitcoin/bitcoin/blob/dcacea096e029a02a937bf96d002ca7e94c48c15/src/consensus/tx_verify.cpp#L32

ACKs for top commit:
  Empact:
    Code Review ACK bitcoin/bitcoin@b00266f

Tree-SHA512: 0eb71591467905434082029128bdca4df94988c372af40dca325654f6c002c72a00c73776cb5e72d6de2b2f218649211a5dbf19300a2e01f1841d6034e0f01e0

Author: MarcoFalke

src/consensus/tx_verify.cpp

@@ -27,9 +27,9 @@ bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
     return true;
 }
 
-std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block)
+std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)
 {
-    assert(prevHeights->size() == tx.vin.size());
+    assert(prevHeights.size() == tx.vin.size());
 
     // Will be set to the equivalent height- and time-based nLockTime
     // values that would be necessary to satisfy all relative lock-
@@ -59,11 +59,11 @@ std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags
         // consensus-enforced meaning at this point.
         if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {
             // The height of this input is not relevant for sequence locks
-            (*prevHeights)[txinIndex] = 0;
+            prevHeights[txinIndex] = 0;
             continue;
         }
 
-        int nCoinHeight = (*prevHeights)[txinIndex];
+        int nCoinHeight = prevHeights[txinIndex];
 
         if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) {
             int64_t nCoinTime = block.GetAncestor(std::max(nCoinHeight-1, 0))->GetMedianTimePast();
@@ -99,7 +99,7 @@ bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> loc
     return true;
 }
 
-bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block)
+bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)
 {
     return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));
 }

src/consensus/tx_verify.h

@@ -66,13 +66,13 @@ bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime);
  * Also removes from the vector of input heights any entries which did not
  * correspond to sequence locked inputs as they do not affect the calculation.
  */
-std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block);
+std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block);
 
 bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair);
 /**
  * Check if transaction is final per BIP 68 sequence numbers and can be included in a block.
  * Consensus critical. Takes as input a list of heights at which tx's inputs (in order) confirmed.
  */
-bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block);
+bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block);
 
 #endif // BITCOIN_CONSENSUS_TX_VERIFY_H

src/test/miner_tests.cpp

@@ -448,7 +448,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     m_node.mempool->addUnchecked(entry.Fee(HIGHFEE).Time(GetTime()).SpendsCoinbase(true).FromTx(tx));
     BOOST_CHECK(CheckFinalTx(CTransaction(tx), flags)); // Locktime passes
     BOOST_CHECK(!TestSequenceLocks(CTransaction(tx), flags)); // Sequence locks fail
-    BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, &prevheights, CreateBlockIndex(::ChainActive().Tip()->nHeight + 2))); // Sequence locks pass on 2nd block
+    BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, prevheights, CreateBlockIndex(::ChainActive().Tip()->nHeight + 2))); // Sequence locks pass on 2nd block
 
     // relative time locked
     tx.vin[0].prevout.hash = txFirst[1]->GetHash();
@@ -461,7 +461,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
 
     for (int i = 0; i < CBlockIndex::nMedianTimeSpan; i++)
         ::ChainActive().Tip()->GetAncestor(::ChainActive().Tip()->nHeight - i)->nTime += 512; //Trick the MedianTimePast
-    BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, &prevheights, CreateBlockIndex(::ChainActive().Tip()->nHeight + 1))); // Sequence locks pass 512 seconds later
+    BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, prevheights, CreateBlockIndex(::ChainActive().Tip()->nHeight + 1))); // Sequence locks pass 512 seconds later
     for (int i = 0; i < CBlockIndex::nMedianTimeSpan; i++)
         ::ChainActive().Tip()->GetAncestor(::ChainActive().Tip()->nHeight - i)->nTime -= 512; //undo tricked MTP
 

src/validation.cpp

@@ -302,7 +302,7 @@ bool CheckSequenceLocks(const CTxMemPool& pool, const CTransaction& tx, int flag
                 prevheights[txinIndex] = coin.nHeight;
             }
         }
-        lockPair = CalculateSequenceLocks(tx, flags, &prevheights, index);
+        lockPair = CalculateSequenceLocks(tx, flags, prevheights, index);
         if (lp) {
             lp->height = lockPair.first;
             lp->time = lockPair.second;
@@ -2172,7 +2172,7 @@ bool CChainState::ConnectBlock(const CBlock& block, BlockValidationState& state,
                 prevheights[j] = view.AccessCoin(tx.vin[j].prevout).nHeight;
             }
 
-            if (!SequenceLocks(tx, nLockTimeFlags, &prevheights, *pindex)) {
+            if (!SequenceLocks(tx, nLockTimeFlags, prevheights, *pindex)) {
                 LogPrintf("ERROR: %s: contains a non-BIP68-final transaction\n", __func__);
                 return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-txns-nonfinal");
             }