#1016 allow meta computed alignment to be smaller than actual alignment

Author: SanderMertens

flecs.c

@@ -25274,10 +25274,15 @@ int flecs_init_type(
             return -1;
         }
         if (comp->size == size && comp->alignment != alignment) {
-            ecs_err("computed size for '%s' matches with actual type but "
-                "alignment is different (%d vs. %d)", ecs_get_name(world, type),
-                    alignment, comp->alignment);
-            return -1;
+            if (comp->alignment < alignment) {
+                ecs_err("computed size for '%s' matches with actual type but "
+                    "alignment is different (%d vs. %d)", ecs_get_name(world, type),
+                        alignment, comp->alignment);
+            } else {
+                /* If this is an existing type, the alignment can be larger but
+                 * not smaller than the computed alignment. */
+                alignment = comp->alignment;
+            }
         }
 
         meta_type->partial = comp->size != size;

src/addons/meta/meta.c

@@ -295,10 +295,15 @@ int flecs_init_type(
             return -1;
         }
         if (comp->size == size && comp->alignment != alignment) {
-            ecs_err("computed size for '%s' matches with actual type but "
-                "alignment is different (%d vs. %d)", ecs_get_name(world, type),
-                    alignment, comp->alignment);
-            return -1;
+            if (comp->alignment < alignment) {
+                ecs_err("computed size for '%s' matches with actual type but "
+                    "alignment is different (%d vs. %d)", ecs_get_name(world, type),
+                        alignment, comp->alignment);
+            } else {
+                /* If this is an existing type, the alignment can be larger but
+                 * not smaller than the computed alignment. */
+                alignment = comp->alignment;
+            }
         }
 
         meta_type->partial = comp->size != size;

test/meta/project.json

@@ -120,7 +120,8 @@
                 "invalid_warning_range",
                 "overlapping_error_warning_range",
                 "overlapping_value_error_range",
-                "overlapping_value_warning_range"
+                "overlapping_value_warning_range",
+                "struct_w_16_alignment"
             ]
         }, {
             "id": "NestedStructTypes",

test/meta/src/StructTypes.c

@@ -771,3 +771,54 @@ void StructTypes_overlapping_value_warning_range() {
 
     ecs_fini(world);
 }
+
+void StructTypes_struct_w_16_alignment() {
+#ifndef _MSC_VER
+    typedef __attribute((aligned(16)))
+#else
+    typedef __declspec(align(16))
+#endif
+    struct T {
+        float x;
+        float y;
+        float z;
+        float w;
+    } T;
+
+    ecs_world_t *world = ecs_init();
+
+    ECS_COMPONENT(world, T);
+
+    ecs_entity_t t = ecs_struct(world, {
+        .entity = ecs_id(T),
+        .members = {
+            {"x", ecs_id(ecs_f32_t)},
+            {"y", ecs_id(ecs_f32_t)},
+            {"z", ecs_id(ecs_f32_t)},
+            {"w", ecs_id(ecs_f32_t)}
+        }
+    });
+
+    test_assert(t != 0);
+    test_str(ecs_get_name(world, t), "T");
+
+    meta_test_struct(world, t, T);
+    meta_test_member(world, t, T, x, ecs_id(ecs_f32_t), 1);
+    meta_test_member(world, t, T, y, ecs_id(ecs_f32_t), 1);
+    meta_test_member(world, t, T, z, ecs_id(ecs_f32_t), 1);
+    meta_test_member(world, t, T, w, ecs_id(ecs_f32_t), 1);
+
+    const EcsComponent *cptr = ecs_get(world, t, EcsComponent);
+    test_assert(cptr != NULL);
+    test_int(cptr->size, sizeof(T));
+    test_int(cptr->alignment, 16);
+
+    const EcsMetaType *mptr = ecs_get(world, t, EcsMetaType);
+    test_assert(mptr != NULL);
+    test_bool(mptr->partial, false);
+    test_bool(mptr->existing, true);
+    test_int(mptr->size, sizeof(T));
+    test_int(mptr->alignment, 16);
+
+    ecs_fini(world);
+}

test/meta/src/main.c

@@ -110,6 +110,7 @@ void StructTypes_invalid_warning_range(void);
 void StructTypes_overlapping_error_warning_range(void);
 void StructTypes_overlapping_value_error_range(void);
 void StructTypes_overlapping_value_warning_range(void);
+void StructTypes_struct_w_16_alignment(void);
 
 // Testsuite 'NestedStructTypes'
 void NestedStructTypes_1_bool(void);
@@ -1345,6 +1346,10 @@ bake_test_case StructTypes_testcases[] = {
     {
         "overlapping_value_warning_range",
         StructTypes_overlapping_value_warning_range
+    },
+    {
+        "struct_w_16_alignment",
+        StructTypes_struct_w_16_alignment
     }
 };
 
@@ -4679,7 +4684,7 @@ static bake_test_suite suites[] = {
         "StructTypes",
         NULL,
         NULL,
-        27,
+        28,
         StructTypes_testcases
     },
     {