[refactor] put finality and maturity checking into a lambda

No behavior change.

src/txmempool.cpp

@@ -638,8 +638,13 @@ void CTxMemPool::removeForReorg(CChainState& active_chainstate, int flags)
 {
     // Remove transactions spending a coinbase which are now immature and no-longer-final transactions
     AssertLockHeld(cs);
-    setEntries txToRemove;
-    for (indexed_transaction_set::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
+    AssertLockHeld(::cs_main);
+
+    const auto check_final_and_mature = [this, &active_chainstate, flags](txiter it)
+        EXCLUSIVE_LOCKS_REQUIRED(cs, ::cs_main) {
+        bool should_remove = false;
+        AssertLockHeld(cs);
+        AssertLockHeld(::cs_main);
         const CTransaction& tx = it->GetTx();
         LockPoints lp = it->GetLockPoints();
         const bool validLP = TestLockPointValidity(active_chainstate.m_chain, &lp);
@@ -648,7 +653,7 @@ void CTxMemPool::removeForReorg(CChainState& active_chainstate, int flags)
             || !CheckSequenceLocks(active_chainstate.m_chain.Tip(), view_mempool, tx, flags, &lp, validLP)) {
             // Note if CheckSequenceLocks fails the LockPoints may still be invalid
             // So it's critical that we remove the tx and not depend on the LockPoints.
-            txToRemove.insert(it);
+            should_remove = true;
         } else if (it->GetSpendsCoinbase()) {
             for (const CTxIn& txin : tx.vin) {
                 indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
@@ -658,11 +663,17 @@ void CTxMemPool::removeForReorg(CChainState& active_chainstate, int flags)
                 if (m_check_ratio != 0) assert(!coin.IsSpent());
                 unsigned int nMemPoolHeight = active_chainstate.m_chain.Tip()->nHeight + 1;
                 if (coin.IsSpent() || (coin.IsCoinBase() && ((signed long)nMemPoolHeight) - coin.nHeight < COINBASE_MATURITY)) {
-                    txToRemove.insert(it);
+                    should_remove = true;
                     break;
                 }
             }
         }
+        return should_remove; 
+    };
+
+    setEntries txToRemove;
+    for (indexed_transaction_set::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
+        if (check_final_and_mature(it)) txToRemove.insert(it);
     }
     setEntries setAllRemoves;
     for (txiter it : txToRemove) {