Improve check_bounds init check.

src/backend/backend.h

@@ -335,6 +335,12 @@ namespace snmalloc
         UNUSED(local_state);
         return concretePagemap.get_bounds();
       }
+
+      static bool is_initialised(LocalState* ls)
+      {
+        UNUSED(ls);
+        return concretePagemap.is_initialised();
+      }
     };
 
   private:

src/backend/pagemap.h

@@ -278,6 +278,14 @@ namespace snmalloc
         return body[p >> SHIFT];
     }
 
+    /**
+     * Check if the pagemap has been initialised.
+     */
+    [[nodiscard]] bool is_initialised() const
+    {
+      return body_opt != nullptr;
+    }
+
     /**
      * Return the starting address corresponding to a given entry within the
      * Pagemap. Also checks that the reference actually points to a valid entry.

src/mem/localalloc.h

@@ -772,6 +772,16 @@ namespace snmalloc
 #endif
     }
 
+    bool check_bounds(const void* p, size_t s)
+    {
+      auto ls = core_alloc->backend_state_ptr();
+      if (SNMALLOC_LIKELY(SharedStateHandle::Pagemap::is_initialised(ls)))
+      {
+        return remaining_bytes(p) >= s;
+      }
+      return true;
+    }
+
     /**
      * Returns the byte offset into an object.
      *

src/override/memcpy.cc

@@ -137,7 +137,7 @@ namespace
       auto& alloc = ThreadAlloc::get();
       void* p = const_cast<void*>(ptr);
 
-      if (SNMALLOC_UNLIKELY(alloc.remaining_bytes(ptr) < len))
+      if (SNMALLOC_UNLIKELY(!alloc.check_bounds(ptr, len)))
       {
         if constexpr (FailFast)
         {

src/test/perf/memcpy/memcpy.cc

@@ -112,7 +112,7 @@ int main(int argc, char** argv)
   };
 
   std::vector<size_t> sizes;
-  for (size_t size = 1; size < 64; size++)
+  for (size_t size = 0; size < 64; size++)
   {
     sizes.push_back(size);
   }