Address code review: fix sizeof guard, improve comments

Copilot · syoyo · Copilot · commit 614cca0d95a3 · 2026-03-17T15:04:52.000Z
Co-authored-by: syoyo &lt;18676+syoyo@users.noreply.github.com&gt;
diff --git a/tests/tester.cc b/tests/tester.cc
@@ -4153,8 +4153,8 @@ void test_loadobjopt_nan_inf_values() {
 
 void test_arena_adapter_overflow_guard() {
   // Verify that arena_adapter::allocate rejects SIZE_MAX/sizeof(T) overflow.
-  // We can't actually allocate SIZE_MAX bytes, but we can verify the function
-  // returns nullptr (when exceptions are disabled, the default).
+  // When TINYOBJLOADER_ENABLE_EXCEPTION is not defined, the allocator returns
+  // nullptr on overflow.  When exceptions are enabled, it throws std::bad_alloc.
   tinyobj::ArenaAllocator arena;
   tinyobj::arena_adapter<double> adapter(&arena);
   // Request an allocation that would overflow size_t when multiplied by
diff --git a/tiny_obj_loader.h b/tiny_obj_loader.h
@@ -827,7 +827,7 @@ class arena_adapter {
       : arena_(other.arena()) {}
 
   T *allocate(size_t n) {
-    if (sizeof(T) > 1 && n > SIZE_MAX / sizeof(T)) {
+    if (n > SIZE_MAX / sizeof(T)) {
 #ifdef TINYOBJLOADER_ENABLE_EXCEPTION
       throw std::bad_alloc();
 #else
@@ -9856,8 +9856,9 @@ void *ArenaAllocator::allocate(size_t bytes, size_t alignment) {
   size_t space = b->capacity;
   void *ptr = b->data;
   if (!std::align(alignment, bytes, ptr, space)) {
-    // Should never happen: block capacity >= bytes + alignment, but guard
-    // against implementation quirks.
+    // Defensive guard: the block was allocated with capacity >= bytes + alignment,
+    // so alignment should always succeed.  This handles edge cases where the
+    // capacity was insufficient due to unusual alignment requirements.
 #ifdef TINYOBJLOADER_ENABLE_EXCEPTION
     throw std::bad_alloc();
 #else
