merge bitcoin#27011: Add simulation-based CCoinsViewCache fuzzer

src/Makefile.test.include

@@ -252,6 +252,7 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/chain.cpp \
  test/fuzz/checkqueue.cpp \
  test/fuzz/coins_view.cpp \
+ test/fuzz/coinscache_sim.cpp \
  test/fuzz/connman.cpp \
  test/fuzz/crypto.cpp \
  test/fuzz/crypto_aes256.cpp \

src/coins.cpp

@@ -31,7 +31,10 @@ bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock,
 std::unique_ptr<CCoinsViewCursor> CCoinsViewBacked::Cursor() const { return base->Cursor(); }
 size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
 
-CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), cachedCoinsUsage(0) {}
+CCoinsViewCache::CCoinsViewCache(CCoinsView* baseIn, bool deterministic) :
+    CCoinsViewBacked(baseIn), m_deterministic(deterministic),
+    cacheCoins(0, SaltedOutpointHasher(/*deterministic=*/deterministic))
+{}
 
 size_t CCoinsViewCache::DynamicMemoryUsage() const {
     return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
@@ -292,7 +295,24 @@ void CCoinsViewCache::ReallocateCache()
     // Cache should be empty when we're calling this.
     assert(cacheCoins.size() == 0);
     cacheCoins.~CCoinsMap();
-    ::new (&cacheCoins) CCoinsMap();
+    ::new (&cacheCoins) CCoinsMap(0, SaltedOutpointHasher(/*deterministic=*/m_deterministic));
+}
+
+void CCoinsViewCache::SanityCheck() const
+{
+    size_t recomputed_usage = 0;
+    for (const auto& [_, entry] : cacheCoins) {
+        unsigned attr = 0;
+        if (entry.flags & CCoinsCacheEntry::DIRTY) attr |= 1;
+        if (entry.flags & CCoinsCacheEntry::FRESH) attr |= 2;
+        if (entry.coin.IsSpent()) attr |= 4;
+        // Only 5 combinations are possible.
+        assert(attr != 2 && attr != 4 && attr != 7);
+
+        // Recompute cachedCoinsUsage.
+        recomputed_usage += entry.coin.DynamicMemoryUsage();
+    }
+    assert(recomputed_usage == cachedCoinsUsage);
 }
 
 static const size_t MAX_OUTPUTS_PER_BLOCK = MaxBlockSize() /  ::GetSerializeSize(CTxOut(), PROTOCOL_VERSION);

src/coins.h

@@ -212,6 +212,9 @@ class CCoinsViewBacked : public CCoinsView
 /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
 class CCoinsViewCache : public CCoinsViewBacked
 {
+private:
+    const bool m_deterministic;
+
 protected:
     /**
      * Make mutable so that we can "fill the cache" even from Get-methods
@@ -221,10 +224,10 @@ class CCoinsViewCache : public CCoinsViewBacked
     mutable CCoinsMap cacheCoins;
 
     /* Cached dynamic memory usage for the inner Coin objects. */
-    mutable size_t cachedCoinsUsage;
+    mutable size_t cachedCoinsUsage{0};
 
 public:
-    CCoinsViewCache(CCoinsView *baseIn);
+    CCoinsViewCache(CCoinsView *baseIn, bool deterministic = false);
 
     /**
      * By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.
@@ -321,6 +324,9 @@ class CCoinsViewCache : public CCoinsViewBacked
     //! See: https://stackoverflow.com/questions/42114044/how-to-release-unordered-map-memory
     void ReallocateCache();
 
+    //! Run an internal sanity check on the cache data structure. */
+    void SanityCheck() const;
+
 private:
     /**
      * @note this is marked const, but may actually append to `cacheCoins`, increasing

src/test/fuzz/coins_view.cpp

@@ -48,7 +48,7 @@ FUZZ_TARGET_INIT(coins_view, initialize_coins_view)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
     CCoinsView backend_coins_view;
-    CCoinsViewCache coins_view_cache{&backend_coins_view};
+    CCoinsViewCache coins_view_cache{&backend_coins_view, /*deterministic=*/true};
     COutPoint random_out_point;
     Coin random_coin;
     CMutableTransaction random_mutable_transaction;