Merge bitcoin/bitcoin#24565: Remove LOCKTIME_MEDIAN_TIME_PAST constant

fa1fe2e500 Remove LOCKTIME_MEDIAN_TIME_PAST constant (MarcoFalke)

Pull request description:

  The constant is exposed in policy code, which doesn't make sense:
  * Wallet and mempool need to assume the flag to be always active to function properly.
  * Setting (or unsetting) the flag has no effect on policy code.

  The constant is only used in `ContextualCheckBlock` (consensus code) to set a flag and then read the flag again. I think this can be better achieved by using a `bool`. If there is a need to use a flag in the future, it will be trivial to do so then.

  (The previous use for the constant was removed in df562d698a)

ACKs for top commit:
  Sjors:
    utACK fa1fe2e500
  glozow:
    code review ACK fa1fe2e500, AFAICT this is safe and makes sense as `SequenceLocks` doesn't use it, wallet/ATMP no longer need it since #24080, and `ContextualCheckBlock` effectively uses it as a roundabout boolean.
  instagibbs:
    utACK fa1fe2e500

Tree-SHA512: de1972498c545d608a09630d77d8c7e38ed50a6ec40d6c0d720310a1647ed5b48b4ace0078c80db10e7f97aacc552fffae251fe3256e9a19a908b933ba2dc552

src/consensus/consensus.h

@@ -26,7 +26,5 @@ static const size_t MIN_SERIALIZABLE_TRANSACTION_WEIGHT = WITNESS_SCALE_FACTOR *
 /** Flags for nSequence and nLockTime locks */
 /** Interpret sequence numbers as relative lock-time constraints. */
 static constexpr unsigned int LOCKTIME_VERIFY_SEQUENCE = (1 << 0);
-/** Use GetMedianTimePast() instead of nTime for end point timestamp. */
-static constexpr unsigned int LOCKTIME_MEDIAN_TIME_PAST = (1 << 1);
 
 #endif // BITCOIN_CONSENSUS_CONSENSUS_H

src/policy/policy.h

@@ -101,8 +101,7 @@ static constexpr unsigned int STANDARD_SCRIPT_VERIFY_FLAGS{MANDATORY_SCRIPT_VERI
 static constexpr unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS{STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS};
 
 /** Used as the flags parameter to sequence and nLocktime checks in non-consensus code. */
-static constexpr unsigned int STANDARD_LOCKTIME_VERIFY_FLAGS{LOCKTIME_VERIFY_SEQUENCE |
-                                                             LOCKTIME_MEDIAN_TIME_PAST};
+static constexpr unsigned int STANDARD_LOCKTIME_VERIFY_FLAGS{LOCKTIME_VERIFY_SEQUENCE};
 
 CAmount GetDustThreshold(const CTxOut& txout, const CFeeRate& dustRelayFee);
 

src/test/miner_tests.cpp

@@ -370,7 +370,7 @@ void MinerTestingSetup::TestBasicMining(const CChainParams& chainparams, const C
 
     // non-final txs in mempool
     SetMockTime(m_node.chainman->ActiveChain().Tip()->GetMedianTimePast() + 1);
-    const int flags{LOCKTIME_VERIFY_SEQUENCE | LOCKTIME_MEDIAN_TIME_PAST};
+    const int flags{LOCKTIME_VERIFY_SEQUENCE};
     // height map
     std::vector<int> prevheights;
 

src/validation.cpp

@@ -3491,15 +3491,15 @@ static bool ContextualCheckBlock(const CBlock& block, BlockValidationState& stat
     const int nHeight = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
 
     // Enforce BIP113 (Median Time Past).
-    int nLockTimeFlags = 0;
+    bool enforce_locktime_median_time_past{false};
     if (DeploymentActiveAfter(pindexPrev, chainman, Consensus::DEPLOYMENT_CSV)) {
         assert(pindexPrev != nullptr);
-        nLockTimeFlags |= LOCKTIME_MEDIAN_TIME_PAST;
+        enforce_locktime_median_time_past = true;
     }
 
-    int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
-                              ? pindexPrev->GetMedianTimePast()
-                              : block.GetBlockTime();
+    const int64_t nLockTimeCutoff{enforce_locktime_median_time_past ?
+                                      pindexPrev->GetMedianTimePast() :
+                                      block.GetBlockTime()};
 
     // Check that all transactions are finalized
     for (const auto& tx : block.vtx) {