validationcaches: Use size_t for sizes

...also move the 0-clamping logic to ApplyArgsManOptions, where it
   belongs.

src/cuckoocache.h

@@ -328,7 +328,7 @@ public:
     }
 
     /** setup initializes the container to store no more than new_size
-     * elements.
+     * elements and no less than 2 elements.
      *
      * setup should only be called once.
      *

src/kernel/validation_cache_sizes.h

@@ -7,13 +7,13 @@
 
 #include <script/sigcache.h>
 
-#include <cstdint>
+#include <cstddef>
 #include <limits>
 
 namespace kernel {
 struct ValidationCacheSizes {
-    int64_t signature_cache_bytes{DEFAULT_MAX_SIG_CACHE_BYTES / 2};
-    int64_t script_execution_cache_bytes{DEFAULT_MAX_SIG_CACHE_BYTES / 2};
+    size_t signature_cache_bytes{DEFAULT_MAX_SIG_CACHE_BYTES / 2};
+    size_t script_execution_cache_bytes{DEFAULT_MAX_SIG_CACHE_BYTES / 2};
 };
 }
 

src/node/validation_cache_args.cpp

@@ -8,6 +8,9 @@
 
 #include <util/system.h>
 
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <optional>
 
@@ -17,11 +20,14 @@ namespace node {
 void ApplyArgsManOptions(const ArgsManager& argsman, ValidationCacheSizes& cache_sizes)
 {
     if (auto max_size = argsman.GetIntArg("-maxsigcachesize")) {
-        // Multiply first, divide after to avoid integer truncation
-        int64_t size_each = *max_size * (1 << 20) / 2;
+        // 1. When supplied with a max_size of 0, both InitSignatureCache and
+        //    InitScriptExecutionCache create the minimum possible cache (2
+        //    elements). Therefore, we can use 0 as a floor here.
+        // 2. Multiply first, divide after to avoid integer truncation.
+        size_t clamped_size_each = std::max<int64_t>(*max_size, 0) * (1 << 20) / 2;
         cache_sizes = {
-            .signature_cache_bytes = size_each,
-            .script_execution_cache_bytes = size_each,
+            .signature_cache_bytes = clamped_size_each,
+            .script_execution_cache_bytes = clamped_size_each,
         };
     }
 }

src/script/sigcache.cpp

@@ -93,13 +93,9 @@ static CSignatureCache signatureCache;
 
 // To be called once in AppInitMain/BasicTestingSetup to initialize the
 // signatureCache.
-bool InitSignatureCache(int64_t max_size_bytes)
+bool InitSignatureCache(size_t max_size_bytes)
 {
-    // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
-    // setup_bytes creates the minimum possible cache (2 elements).
-    size_t nMaxCacheSize = std::max<int64_t>(max_size_bytes, 0);
-
-    auto setup_results = signatureCache.setup_bytes(nMaxCacheSize);
+    auto setup_results = signatureCache.setup_bytes(max_size_bytes);
     if (!setup_results) return false;
 
     const auto [num_elems, approx_size_bytes] = *setup_results;

src/script/sigcache.h

@@ -32,6 +32,6 @@ public:
     bool VerifySchnorrSignature(Span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const override;
 };
 
-[[nodiscard]] bool InitSignatureCache(int64_t max_size_bytes);
+[[nodiscard]] bool InitSignatureCache(size_t max_size_bytes);
 
 #endif // BITCOIN_SCRIPT_SIGCACHE_H

src/validation.cpp

@@ -1656,7 +1656,7 @@ bool CScriptCheck::operator()() {
 static CuckooCache::cache<uint256, SignatureCacheHasher> g_scriptExecutionCache;
 static CSHA256 g_scriptExecutionCacheHasher;
 
-bool InitScriptExecutionCache(int64_t max_size_bytes)
+bool InitScriptExecutionCache(size_t max_size_bytes)
 {
     // Setup the salted hasher
     uint256 nonce = GetRandHash();
@@ -1665,11 +1665,8 @@ bool InitScriptExecutionCache(int64_t max_size_bytes)
     // just write our 32-byte entropy twice to fill the 64 bytes.
     g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
     g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
-    // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
-    // setup_bytes creates the minimum possible cache (2 elements).
-    size_t nMaxCacheSize = std::max<int64_t>(max_size_bytes, 0);
 
-    auto setup_results = g_scriptExecutionCache.setup_bytes(nMaxCacheSize);
+    auto setup_results = g_scriptExecutionCache.setup_bytes(max_size_bytes);
     if (!setup_results) return false;
 
     const auto [num_elems, approx_size_bytes] = *setup_results;

src/validation.h

@@ -323,7 +323,7 @@ public:
 };
 
 /** Initializes the script-execution cache */
-[[nodiscard]] bool InitScriptExecutionCache(int64_t max_size_bytes);
+[[nodiscard]] bool InitScriptExecutionCache(size_t max_size_bytes);
 
 /** Functions for validating blocks and updating the block tree */