Don't traverse to count; fix memory leak in reset

tests/test_arena_allocator.cpp

@@ -6,17 +6,17 @@
 
 TEST_CASE("ArenaAllocator basic construction") {
   ArenaAllocator arena;
-  CHECK(arena.num_blocks() == 1);
+  CHECK(arena.num_blocks() == 0);
   CHECK(arena.used_bytes() == 0);
-  CHECK(arena.total_allocated() == 1024);
-  CHECK(arena.available_in_current_block() == 1024);
+  CHECK(arena.total_allocated() == 0);
+  CHECK(arena.available_in_current_block() == 0);
 }
 
 TEST_CASE("ArenaAllocator custom initial size") {
   ArenaAllocator arena(2048);
-  CHECK(arena.num_blocks() == 1);
-  CHECK(arena.total_allocated() == 2048);
-  CHECK(arena.available_in_current_block() == 2048);
+  CHECK(arena.num_blocks() == 0);
+  CHECK(arena.total_allocated() == 0);
+  CHECK(arena.available_in_current_block() == 0);
 }
 
 TEST_CASE("ArenaAllocator basic allocation") {
@@ -93,7 +93,7 @@ TEST_CASE("ArenaAllocator block management") {
   SUBCASE("allocation larger than block size grows arena") {
     void *ptr = arena.allocate(200);
     CHECK(ptr != nullptr);
-    CHECK(arena.num_blocks() == 2);
+    CHECK(arena.num_blocks() == 1);
   }
 }
 
@@ -146,12 +146,43 @@ TEST_CASE("ArenaAllocator reset functionality") {
   CHECK(arena.used_bytes() == 50);
 }
 
+TEST_CASE("ArenaAllocator reset memory leak test") {
+  ArenaAllocator arena(32); // Smaller initial size
+
+  // Force multiple blocks
+  arena.allocate(30); // First block (32 bytes)
+  CHECK(arena.num_blocks() == 1);
+
+  arena.allocate(30); // Should create second block (64 bytes due to doubling)
+  CHECK(arena.num_blocks() == 2);
+
+  arena.allocate(100); // Should create third block (128 bytes due to doubling,
+                       // or larger for 100)
+  CHECK(arena.num_blocks() == 3);
+
+  size_t total_before = arena.total_allocated();
+  CHECK(total_before > 32);
+
+  arena.reset();
+
+  // After reset, only first block should remain (others freed to prevent memory
+  // leak)
+  CHECK(arena.num_blocks() == 1);
+  CHECK(arena.total_allocated() == 32); // Only first block size
+  CHECK(arena.used_bytes() == 0);
+
+  // Should be able to use the first block again
+  void *ptr = arena.allocate(20);
+  CHECK(ptr != nullptr);
+  CHECK(arena.used_bytes() == 20);
+}
+
 TEST_CASE("ArenaAllocator memory tracking") {
   ArenaAllocator arena(512);
 
-  CHECK(arena.total_allocated() == 512);
+  CHECK(arena.total_allocated() == 0);
   CHECK(arena.used_bytes() == 0);
-  CHECK(arena.available_in_current_block() == 512);
+  CHECK(arena.available_in_current_block() == 0);
 
   arena.allocate(100);
   CHECK(arena.used_bytes() >= 100);