validation: Don't error if maxsigcachesize exceeds uint32::max

Instead clamp it to uint32::max if it exceeds it.

Co-authored-by: Anthony Towns <aj@erisian.com.au>

src/cuckoocache.h

@@ -14,7 +14,6 @@
 #include <cstring>
 #include <limits>
 #include <memory>
-#include <optional>
 #include <utility>
 #include <vector>
 
@@ -360,16 +359,15 @@ public:
      * structure
      * @returns A pair of the maximum number of elements storable (see setup()
      * documentation for more detail) and the approximate total size of these
-     * elements in bytes or std::nullopt if the size requested is too large.
+     * elements in bytes.
      */
-    std::optional<std::pair<uint32_t, size_t>> setup_bytes(size_t bytes)
+    std::pair<uint32_t, size_t> setup_bytes(size_t bytes)
     {
-        size_t requested_num_elems = bytes / sizeof(Element);
-        if (std::numeric_limits<uint32_t>::max() < requested_num_elems) {
-            return std::nullopt;
-        }
+        uint32_t requested_num_elems(std::min<size_t>(
+            bytes / sizeof(Element),
+            std::numeric_limits<uint32_t>::max()));
 
-        auto num_elems = setup(bytes/sizeof(Element));
+        auto num_elems = setup(requested_num_elems);
 
         size_t approx_size_bytes = num_elems * sizeof(Element);
         return std::make_pair(num_elems, approx_size_bytes);

src/init.cpp

@@ -1156,11 +1156,8 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     ValidationCacheSizes validation_cache_sizes{};
     ApplyArgsManOptions(args, validation_cache_sizes);
-    if (!InitSignatureCache(validation_cache_sizes.signature_cache_bytes)
-        || !InitScriptExecutionCache(validation_cache_sizes.script_execution_cache_bytes))
-    {
-        return InitError(strprintf(_("Unable to allocate memory for -maxsigcachesize: '%s' MiB"), args.GetIntArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_BYTES >> 20)));
-    }
+    (void)InitSignatureCache(validation_cache_sizes.signature_cache_bytes);
+    (void)InitScriptExecutionCache(validation_cache_sizes.script_execution_cache_bytes);
 
     assert(!node.scheduler);
     node.scheduler = std::make_unique<CScheduler>();

src/script/sigcache.cpp

@@ -15,7 +15,6 @@
 
 #include <algorithm>
 #include <mutex>
-#include <optional>
 #include <shared_mutex>
 #include <vector>
 
@@ -77,7 +76,7 @@ public:
         std::unique_lock<std::shared_mutex> lock(cs_sigcache);
         setValid.insert(entry);
     }
-    std::optional<std::pair<uint32_t, size_t>> setup_bytes(size_t n)
+    std::pair<uint32_t, size_t> setup_bytes(size_t n)
     {
         return setValid.setup_bytes(n);
     }
@@ -96,10 +95,7 @@ static CSignatureCache signatureCache;
 // signatureCache.
 bool InitSignatureCache(size_t max_size_bytes)
 {
-    auto setup_results = signatureCache.setup_bytes(max_size_bytes);
-    if (!setup_results) return false;
-
-    const auto [num_elems, approx_size_bytes] = *setup_results;
+    const auto [num_elems, approx_size_bytes] = signatureCache.setup_bytes(max_size_bytes);
     LogPrintf("Using %zu MiB out of %zu MiB requested for signature cache, able to store %zu elements\n",
               approx_size_bytes >> 20, max_size_bytes >> 20, num_elems);
     return true;

src/script/sigcache.h

@@ -10,7 +10,6 @@
 #include <span.h>
 #include <util/hasher.h>
 
-#include <optional>
 #include <vector>
 
 // DoS prevention: limit cache size to 32MiB (over 1000000 entries on 64-bit

src/validation.cpp

@@ -2100,10 +2100,7 @@ bool InitScriptExecutionCache(size_t max_size_bytes)
     g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
     g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
 
-    auto setup_results = g_scriptExecutionCache.setup_bytes(max_size_bytes);
-    if (!setup_results) return false;
-
-    const auto [num_elems, approx_size_bytes] = *setup_results;
+    const auto [num_elems, approx_size_bytes] = g_scriptExecutionCache.setup_bytes(max_size_bytes);
     LogPrintf("Using %zu MiB out of %zu MiB requested for script execution cache, able to store %zu elements\n",
               approx_size_bytes >> 20, max_size_bytes >> 20, num_elems);
     return true;