Merge bitcoin/bitcoin#23325: mempool: delete exists(uint256) function

4307849256761fe2440d82bbec892d0e8e6b4dd4 [mempool] delete exists(uint256) function (glozow)
d50fbd4c5b4bc72415854d582cedf94541a46983 create explicit GenTxid::{Txid, Wtxid} ctors (glozow)

Pull request description:

  We use the same type for txids and wtxids, `uint256`. In places where we want the ability to pass either one, we distinguish them using `GenTxid`.

  The (overloaded) `CTxMemPool::exists()` function is defined as follows:
  ```c
  bool exists(const uint256& txid) const { return exists(GenTxid{false, txid}); }
  ```
  It always assumes that a uint256 is a txid, which is a footgunny interface.
  Querying by wtxid returns a false negative if the transaction has a witness. :bug:

  Another approach would be to try both:
  ```c
  bool exists(const uint256& txid) const { return exists(GenTxid{false, txid}) || exists(GenTxid{false, txid}); }
  ```
  But that's slower and wrongfully placing the burden on the callee; the caller always knows whether the hash is a txid or a wtxid.

ACKs for top commit:
  laanwj:
    Code review ACK 4307849256761fe2440d82bbec892d0e8e6b4dd4
  jnewbery:
    Tested and code review ACK 4307849256761fe2440d82bbec892d0e8e6b4dd4
  MarcoFalke:
    review ACK 4307849256761fe2440d82bbec892d0e8e6b4dd4 👘

Tree-SHA512: 8ed167a96f3124b6c14e41073c8358658114ce121a15a4cca2db7a5ac565903a6236e34e88ac03382b8bb8b68e3999abbfc5718bc8c22476554d6b49a5298eec

9 files changed, 31 insertions, 30 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 22586ba7da..9c8909f742 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -3247,7 +3247,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
                 // Always relay transactions received from peers with forcerelay
                 // permission, even if they were already in the mempool, allowing
                 // the node to function as a gateway for nodes hidden behind it.
-                if (!m_mempool.exists(tx.GetHash())) {
+                if (!m_mempool.exists(GenTxid::Txid(tx.GetHash()))) {
                     LogPrintf("Not relaying non-mempool transaction %s from forcerelay peer=%d\n", tx.GetHash().ToString(), pfrom.GetId());
                 } else {
                     LogPrintf("Force relaying tx %s from peer=%d\n", tx.GetHash().ToString(), pfrom.GetId());
diff --git a/src/node/interfaces.cpp b/src/node/interfaces.cpp
index 73f4036057..192caf7994 100644
--- a/src/node/interfaces.cpp
+++ b/src/node/interfaces.cpp
@@ -555,7 +555,7 @@ public:
     {
         if (!m_node.mempool) return false;
         LOCK(m_node.mempool->cs);
-        return m_node.mempool->exists(txid);
+        return m_node.mempool->exists(GenTxid::Txid(txid));
     }
     bool hasDescendantsInMempool(const uint256& txid) override
     {
diff --git a/src/policy/rbf.cpp b/src/policy/rbf.cpp
index 7ac2e22006..7e6b0cf245 100644
--- a/src/policy/rbf.cpp
+++ b/src/policy/rbf.cpp
@@ -22,7 +22,7 @@ RBFTransactionState IsRBFOptIn(const CTransaction& tx, const CTxMemPool& pool)
 
     // If this transaction is not in our mempool, then we can't be sure
     // we will know about all its inputs.
-    if (!pool.exists(tx.GetHash())) {
+    if (!pool.exists(GenTxid::Txid(tx.GetHash()))) {
         return RBFTransactionState::UNKNOWN;
     }
 
@@ -98,7 +98,7 @@ std::optional<std::string> HasNoNewUnconfirmed(const CTransaction& tx,
         if (!parents_of_conflicts.count(tx.vin[j].prevout.hash)) {
             // Rather than check the UTXO set - potentially expensive - it's cheaper to just check
             // if the new input refers to a tx that's in the mempool.
-            if (pool.exists(tx.vin[j].prevout.hash)) {
+            if (pool.exists(GenTxid::Txid(tx.vin[j].prevout.hash))) {
                 return strprintf("replacement %s adds unconfirmed input, idx %d",
                                  tx.GetHash().ToString(), j);
             }
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index 46db39f8db..d7a85015ef 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -393,6 +393,8 @@ class GenTxid
     uint256 m_hash;
 public:
     GenTxid(bool is_wtxid, const uint256& hash) : m_is_wtxid(is_wtxid), m_hash(hash) {}
+    static GenTxid Txid(const uint256& hash) { return GenTxid{false, hash}; }
+    static GenTxid Wtxid(const uint256& hash) { return GenTxid{true, hash}; }
     bool IsWtxid() const { return m_is_wtxid; }
     const uint256& GetHash() const { return m_hash; }
     friend bool operator==(const GenTxid& a, const GenTxid& b) { return a.m_is_wtxid == b.m_is_wtxid && a.m_hash == b.m_hash; }
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index dadd82e03f..aa7a55e7a9 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -516,7 +516,7 @@ static void entryToJSON(const CTxMemPool& pool, UniValue& info, const CTxMemPool
     std::set<std::string> setDepends;
     for (const CTxIn& txin : tx.vin)
     {
-        if (pool.exists(txin.prevout.hash))
+        if (pool.exists(GenTxid::Txid(txin.prevout.hash)))
             setDepends.insert(txin.prevout.hash.ToString());
     }
 
diff --git a/src/test/mempool_tests.cpp b/src/test/mempool_tests.cpp
index bf36f8a6c9..b3497b8ef8 100644
--- a/src/test/mempool_tests.cpp
+++ b/src/test/mempool_tests.cpp
@@ -444,12 +444,12 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
     pool.addUnchecked(entry.Fee(5000LL).FromTx(tx2));
 
     pool.TrimToSize(pool.DynamicMemoryUsage()); // should do nothing
-    BOOST_CHECK(pool.exists(tx1.GetHash()));
-    BOOST_CHECK(pool.exists(tx2.GetHash()));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx1.GetHash())));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx2.GetHash())));
 
     pool.TrimToSize(pool.DynamicMemoryUsage() * 3 / 4); // should remove the lower-feerate transaction
-    BOOST_CHECK(pool.exists(tx1.GetHash()));
-    BOOST_CHECK(!pool.exists(tx2.GetHash()));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx1.GetHash())));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx2.GetHash())));
 
     pool.addUnchecked(entry.FromTx(tx2));
     CMutableTransaction tx3 = CMutableTransaction();
@@ -462,14 +462,14 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
     pool.addUnchecked(entry.Fee(20000LL).FromTx(tx3));
 
     pool.TrimToSize(pool.DynamicMemoryUsage() * 3 / 4); // tx3 should pay for tx2 (CPFP)
-    BOOST_CHECK(!pool.exists(tx1.GetHash()));
-    BOOST_CHECK(pool.exists(tx2.GetHash()));
-    BOOST_CHECK(pool.exists(tx3.GetHash()));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx1.GetHash())));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx2.GetHash())));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx3.GetHash())));
 
     pool.TrimToSize(GetVirtualTransactionSize(CTransaction(tx1))); // mempool is limited to tx1's size in memory usage, so nothing fits
-    BOOST_CHECK(!pool.exists(tx1.GetHash()));
-    BOOST_CHECK(!pool.exists(tx2.GetHash()));
-    BOOST_CHECK(!pool.exists(tx3.GetHash()));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx1.GetHash())));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx2.GetHash())));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx3.GetHash())));
 
     CFeeRate maxFeeRateRemoved(25000, GetVirtualTransactionSize(CTransaction(tx3)) + GetVirtualTransactionSize(CTransaction(tx2)));
     BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), maxFeeRateRemoved.GetFeePerK() + 1000);
@@ -529,19 +529,19 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
 
     // we only require this to remove, at max, 2 txn, because it's not clear what we're really optimizing for aside from that
     pool.TrimToSize(pool.DynamicMemoryUsage() - 1);
-    BOOST_CHECK(pool.exists(tx4.GetHash()));
-    BOOST_CHECK(pool.exists(tx6.GetHash()));
-    BOOST_CHECK(!pool.exists(tx7.GetHash()));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx4.GetHash())));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx6.GetHash())));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx7.GetHash())));
 
-    if (!pool.exists(tx5.GetHash()))
+    if (!pool.exists(GenTxid::Txid(tx5.GetHash())))
         pool.addUnchecked(entry.Fee(1000LL).FromTx(tx5));
     pool.addUnchecked(entry.Fee(9000LL).FromTx(tx7));
 
     pool.TrimToSize(pool.DynamicMemoryUsage() / 2); // should maximize mempool size by only removing 5/7
-    BOOST_CHECK(pool.exists(tx4.GetHash()));
-    BOOST_CHECK(!pool.exists(tx5.GetHash()));
-    BOOST_CHECK(pool.exists(tx6.GetHash()));
-    BOOST_CHECK(!pool.exists(tx7.GetHash()));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx4.GetHash())));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx5.GetHash())));
+    BOOST_CHECK(pool.exists(GenTxid::Txid(tx6.GetHash())));
+    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx7.GetHash())));
 
     pool.addUnchecked(entry.Fee(1000LL).FromTx(tx5));
     pool.addUnchecked(entry.Fee(9000LL).FromTx(tx7));
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 5a93f30c8a..b945659c0d 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -969,7 +969,7 @@ CTxMemPool::setEntries CTxMemPool::GetIterSet(const std::set<uint256>& hashes) c
 bool CTxMemPool::HasNoInputsOf(const CTransaction &tx) const
 {
     for (unsigned int i = 0; i < tx.vin.size(); i++)
-        if (exists(tx.vin[i].prevout.hash))
+        if (exists(GenTxid::Txid(tx.vin[i].prevout.hash)))
             return false;
     return true;
 }
@@ -1140,7 +1140,7 @@ void CTxMemPool::TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpends
         if (pvNoSpendsRemaining) {
             for (const CTransaction& tx : txn) {
                 for (const CTxIn& txin : tx.vin) {
-                    if (exists(txin.prevout.hash)) continue;
+                    if (exists(GenTxid::Txid(txin.prevout.hash))) continue;
                     pvNoSpendsRemaining->push_back(txin.prevout);
                 }
             }
diff --git a/src/txmempool.h b/src/txmempool.h
index 460e9d0ceb..1fd0c70891 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -782,7 +782,6 @@ public:
         }
         return (mapTx.count(gtxid.GetHash()) != 0);
     }
-    bool exists(const uint256& txid) const { return exists(GenTxid{false, txid}); }
 
     CTransactionRef get(const uint256& hash) const;
     txiter get_iter_from_wtxid(const uint256& wtxid) const EXCLUSIVE_LOCKS_REQUIRED(cs)
@@ -802,7 +801,7 @@ public:
         LOCK(cs);
         // Sanity check the transaction is in the mempool & insert into
         // unbroadcast set.
-        if (exists(txid)) m_unbroadcast_txids.insert(txid);
+        if (exists(GenTxid::Txid(txid))) m_unbroadcast_txids.insert(txid);
     };
 
     /** Removes a transaction from the unbroadcast set */
diff --git a/src/validation.cpp b/src/validation.cpp
index ff71020ebb..8938948d06 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -355,7 +355,7 @@ void CChainState::MaybeUpdateMempoolForReorg(
             // If the transaction doesn't make it in to the mempool, remove any
             // transactions that depend on it (which would now be orphans).
             m_mempool->removeRecursive(**it, MemPoolRemovalReason::REORG);
-        } else if (m_mempool->exists((*it)->GetHash())) {
+        } else if (m_mempool->exists(GenTxid::Txid((*it)->GetHash()))) {
             vHashUpdate.push_back((*it)->GetHash());
         }
         ++it;
@@ -908,7 +908,7 @@ bool MemPoolAccept::Finalize(const ATMPArgs& args, Workspace& ws)
     // trim mempool and check if tx was trimmed
     if (!bypass_limits) {
         LimitMempoolSize(m_pool, m_active_chainstate.CoinsTip(), gArgs.GetIntArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetIntArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
-        if (!m_pool.exists(hash))
+        if (!m_pool.exists(GenTxid::Txid(hash)))
             return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "mempool full");
     }
     return true;
@@ -4500,7 +4500,7 @@ bool LoadMempool(CTxMemPool& pool, CChainState& active_chainstate, FopenFn mocka
                     // wallet(s) having loaded it while we were processing
                     // mempool transactions; consider these as valid, instead of
                     // failed, but mark them as 'already there'
-                    if (pool.exists(tx->GetHash())) {
+                    if (pool.exists(GenTxid::Txid(tx->GetHash()))) {
                         ++already_there;
                     } else {
                         ++failed;