[Core]: Fix entity generation overflow

src/gamecoe/entity/entities.cpp

@@ -33,9 +33,6 @@ namespace gamecoe
             id = m_recycle_ids.back();
             m_recycle_ids.pop_back();
             generation = m_generations[id];
-            GAMECOE_ASSERT_GUARD(generation <= entity::MAX_GENERATIONS,
-                                 "entities::create(): recycled entity generation exceeds maximum",
-                                 entity::invalid());
             m_self_active[id] = true;
         }
 
@@ -85,7 +82,9 @@ namespace gamecoe
                 to_destroy.insert(to_destroy.end(), kids->handles.begin(), kids->handles.end());
 
             m_generations[current.id()]++;
-            m_recycle_ids.push_back(current.id());
+            bool exhausted = m_generations[current.id()] > entity::MAX_GENERATIONS;
+            GAMECOE_ASSERT_LOG(!exhausted, "entities::destroy(): id's generation reached the maximum, permanently retiring this id");
+            if (!exhausted) m_recycle_ids.push_back(current.id());
 
             for (auto &pool : m_pools) if (pool) pool->remove(current);
         }

tests/entity/entities_tests.cpp

@@ -119,6 +119,48 @@ TEST_F(EntitiesTests, EntityLifecycle)
     }
 }
 
+//==============================================================================
+//                Recycle Generation Overflow (destroy()-side guard)
+//==============================================================================
+
+#ifndef NDEBUG
+TEST_F(EntitiesTests, RecycleGenerationOverflowIsGuarded)
+{
+    mgr.clear();
+    entity e = mgr.create();
+
+    // Drive this one id's generation up to MAX_GENERATIONS by repeatedly recycling it: as the
+    // only entity in the recycle stack, each destroy()/create() pair recycles the same id (LIFO
+    // via m_recycle_ids.back()/pop_back()).
+    for (std::uint16_t gen = 0; gen < entity::MAX_GENERATIONS; ++gen)
+    {
+        mgr.destroy(e);
+        e = mgr.create();
+    }
+
+    EXPECT_DEATH(mgr.destroy(e), "id's generation reached the maximum");
+}
+#else
+TEST_F(EntitiesTests, RecycleGenerationOverflowRetiresId)
+{
+    mgr.clear();
+    entity e = mgr.create();
+    std::uint32_t id = e.id();
+
+    for (std::uint16_t gen = 0; gen < entity::MAX_GENERATIONS; ++gen)
+    {
+        mgr.destroy(e);
+        e = mgr.create();
+    }
+
+    mgr.destroy(e);
+
+    // Id is permanently retired - never handed out again by a later create() call.
+    for (int i = 0; i < 100; ++i)
+        EXPECT_NE(mgr.create().id(), id);
+}
+#endif
+
 //==============================================================================
 //                        Move Semantics
 //==============================================================================