From 94ef082925c324886dd8300f6dbec2ebfb8f0c18 Mon Sep 17 00:00:00 2001
From: Kittywhiskers Van Gogh <63189531+kittywhiskers@users.noreply.github.com>
Date: Fri, 11 Sep 2020 14:33:00 -0700
Subject: [PATCH] partial bitcoin#19953: Keep spent outputs in
 PrecomputedTransactionData

---
 src/script/interpreter.cpp | 10 ++++++----
 src/script/interpreter.h   |  4 +++-
 src/validation.cpp         | 20 +++++++++++++-------
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index a9d29078108ebc..18ae1ea355e3ad 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1437,10 +1437,12 @@ uint256 GetOutputsHash(const T& txTo)
 } // namespace
 
 template <class T>
-void PrecomputedTransactionData::Init(const T& txTo)
+void PrecomputedTransactionData::Init(const T& txTo, std::vector<CTxOut>&& spent_outputs)
 {
     assert(!m_ready);
 
+    m_spent_outputs = std::move(spent_outputs);
+
     // Cache is calculated only for transactions with witness
     if (txTo.HasWitness()) {
         hashPrevouts = GetPrevoutHash(txTo);
@@ -1454,14 +1456,14 @@ void PrecomputedTransactionData::Init(const T& txTo)
 template <class T>
 PrecomputedTransactionData::PrecomputedTransactionData(const T& txTo)
 {
-    Init(txTo);
+    Init(txTo, {});
 }
 
 // explicit instantiation
 template PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo);
 template PrecomputedTransactionData::PrecomputedTransactionData(const CMutableTransaction& txTo);
-template void PrecomputedTransactionData::Init(const CTransaction& txTo);
-template void PrecomputedTransactionData::Init(const CMutableTransaction& txTo);
+template void PrecomputedTransactionData::Init(const CTransaction& txTo, std::vector<CTxOut>&& spent_outputs);
+template void PrecomputedTransactionData::Init(const CMutableTransaction& txTo, std::vector<CTxOut>&& spent_outputs);
 
 template <class T>
 uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache)
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
index 88779c334f7b94..929e50275dc2ca 100644
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -15,6 +15,7 @@
 class CPubKey;
 class CScript;
 class CTransaction;
+class CTxOut;
 class uint256;
 
 /** Signature hash types/flags */
@@ -109,11 +110,12 @@ struct PrecomputedTransactionData
 {
     uint256 hashPrevouts, hashSequence, hashOutputs;
     bool m_ready = false;
+    std::vector<CTxOut> m_spent_outputs;
 
     PrecomputedTransactionData() = default;
 
     template <class T>
-    void Init(const T& tx);
+    void Init(const T& tx, std::vector<CTxOut>&& spent_outputs);
 
     template <class T>
     explicit PrecomputedTransactionData(const T& tx);
diff --git a/src/validation.cpp b/src/validation.cpp
index 640de59f93b884..ba0d4eafa202a0 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1453,14 +1453,20 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
             }
 
             if (!txdata.m_ready) {
-                txdata.Init(tx);
+                std::vector<CTxOut> spent_outputs;
+                spent_outputs.reserve(tx.vin.size());
+
+                for (const auto& txin : tx.vin) {
+                    const COutPoint& prevout = txin.prevout;
+                    const Coin& coin = inputs.AccessCoin(prevout);
+                    assert(!coin.IsSpent());
+                    spent_outputs.emplace_back(coin.out);
+                }
+                txdata.Init(tx, std::move(spent_outputs));
             }
+            assert(txdata.m_spent_outputs.size() == tx.vin.size());
 
             for (unsigned int i = 0; i < tx.vin.size(); i++) {
-                const COutPoint &prevout = tx.vin[i].prevout;
-                const Coin& coin = inputs.AccessCoin(prevout);
-                assert(!coin.IsSpent());
-
                 // We very carefully only pass in things to CScriptCheck which
                 // are clearly committed to by tx' witness hash. This provides
                 // a sanity check that our caching is not introducing consensus
@@ -1468,7 +1474,7 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
                 // spent being checked as a part of CScriptCheck.
 
                 // Verify signature
-                CScriptCheck check(coin.out, tx, i, flags, cacheSigStore, &txdata);
+                CScriptCheck check(txdata.m_spent_outputs[i], tx, i, flags, cacheSigStore, &txdata);
                 if (pvChecks) {
                     pvChecks->push_back(CScriptCheck());
                     check.swap(pvChecks->back());
@@ -1483,7 +1489,7 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
                         // arguments; if so, don't trigger DoS protection to
                         // avoid splitting the network between upgraded and
                         // non-upgraded nodes.
-                        CScriptCheck check2(coin.out, tx, i,
+                        CScriptCheck check2(txdata.m_spent_outputs[i], tx, i,
                                 (flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS) | SCRIPT_ENABLE_DIP0020_OPCODES, cacheSigStore, &txdata);
                         if (check2())
                             return state.Invalid(false, REJECT_NONSTANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));