const string opaque type implementation

distr/flecs.c

@@ -48537,6 +48537,13 @@ size_t flecs_addon_vec_count(const void *ptr) {
     return flecs_ito(size_t, count);
 }
 
+static
+int flecs_const_str_serialize(const ecs_serializer_t *ser, const void *ptr) {
+    char **data = ECS_CONST_CAST(char**, ptr);
+    ser->value(ser, ecs_id(ecs_string_t), data);
+    return 0;
+}
+
 /* Initialize reflection data for core components */
 static
 void flecs_meta_import_core_definitions(
@@ -48557,6 +48564,29 @@ void flecs_meta_import_core_definitions(
         }
     });
 
+    /* Define const string as an opaque type that maps to string
+       This enables reflection for strings that are in .rodata,
+       (read-only) so that the meta add-on does not try to free them.
+       This opaque type defines how to serialize (read) the string,
+       but won't let users assign a new value.
+    */
+    ecs_entity_t const_string = ecs_opaque(world, {
+        .entity = ecs_component(world, {
+              .entity = ecs_entity(world, {
+                .name = "flecs.core.const_string_t",
+                .root_sep = ""
+            }),
+            .type = {
+                .size = ECS_SIZEOF(const char*),
+                .alignment = ECS_ALIGNOF(const char*)
+            }          
+        }),
+        .type = {
+            .as_type = ecs_id(ecs_string_t),
+            .serialize = flecs_const_str_serialize,       
+        }
+    });
+
     ecs_entity_t string_vec = ecs_vector(world, {
         .entity = ecs_entity(world, { 
             .name = "flecs.core.string_vec_t",
@@ -48589,9 +48619,9 @@ void flecs_meta_import_core_definitions(
             .root_sep = ""
         }),
         .members = {
-            { .name = "compiler", .type = ecs_id(ecs_string_t) },
+            { .name = "compiler", .type = const_string },
             { .name = "addons", .type = addon_vec },
-            { .name = "version", .type = ecs_id(ecs_string_t) },
+            { .name = "version", .type = const_string },
             { .name = "version_major", .type = ecs_id(ecs_i16_t) },
             { .name = "version_minor", .type = ecs_id(ecs_i16_t) },
             { .name = "version_patch", .type = ecs_id(ecs_i16_t) },

src/addons/meta/definitions.c

@@ -30,6 +30,13 @@ size_t flecs_addon_vec_count(const void *ptr) {
     return flecs_ito(size_t, count);
 }
 
+static
+int flecs_const_str_serialize(const ecs_serializer_t *ser, const void *ptr) {
+    char **data = ECS_CONST_CAST(char**, ptr);
+    ser->value(ser, ecs_id(ecs_string_t), data);
+    return 0;
+}
+
 /* Initialize reflection data for core components */
 static
 void flecs_meta_import_core_definitions(
@@ -50,6 +57,29 @@ void flecs_meta_import_core_definitions(
         }
     });
 
+    /* Define const string as an opaque type that maps to string
+       This enables reflection for strings that are in .rodata,
+       (read-only) so that the meta add-on does not try to free them.
+       This opaque type defines how to serialize (read) the string,
+       but won't let users assign a new value.
+    */
+    ecs_entity_t const_string = ecs_opaque(world, {
+        .entity = ecs_component(world, {
+              .entity = ecs_entity(world, {
+                .name = "flecs.core.const_string_t",
+                .root_sep = ""
+            }),
+            .type = {
+                .size = ECS_SIZEOF(const char*),
+                .alignment = ECS_ALIGNOF(const char*)
+            }          
+        }),
+        .type = {
+            .as_type = ecs_id(ecs_string_t),
+            .serialize = flecs_const_str_serialize,       
+        }
+    });
+
     ecs_entity_t string_vec = ecs_vector(world, {
         .entity = ecs_entity(world, { 
             .name = "flecs.core.string_vec_t",
@@ -82,9 +112,9 @@ void flecs_meta_import_core_definitions(
             .root_sep = ""
         }),
         .members = {
-            { .name = "compiler", .type = ecs_id(ecs_string_t) },
+            { .name = "compiler", .type = const_string },
             { .name = "addons", .type = addon_vec },
-            { .name = "version", .type = ecs_id(ecs_string_t) },
+            { .name = "version", .type = const_string },
             { .name = "version_major", .type = ecs_id(ecs_i16_t) },
             { .name = "version_minor", .type = ecs_id(ecs_i16_t) },
             { .name = "version_patch", .type = ecs_id(ecs_i16_t) },

test/meta/project.json

@@ -938,7 +938,8 @@
                 "deser_entity_from_json",
                 "ser_deser_world_w_ser_opaque",
                 "ser_deser_entity",
-                "ser_deser_0_entity"
+                "ser_deser_0_entity",
+                "const_string"
             ]
         }, {
             "id": "Misc",

test/meta/src/OpaqueTypes.c

@@ -637,3 +637,51 @@ void OpaqueTypes_ser_deser_0_entity(void) {
 
     ecs_fini(world);
 }
+
+
+void OpaqueTypes_const_string(void) {
+
+    typedef struct test_string_struct {
+        const char *value;
+    } test_string_struct;
+
+    const char *test_string = "Const String. Don't try to free me!";
+
+    ecs_world_t *world = ecs_init();
+
+    // Lookup const string type:
+    ecs_entity_t const_string = ecs_lookup(world, "flecs.core.const_string_t");
+
+    // Create a reflection interface for `test_struct`:
+    ecs_entity_t test_struct = ecs_struct(world, {
+    .entity = ecs_entity(world, {
+        .name = "test_struct", .root_sep = ""}),
+        .members = {
+            {
+                .name = "value",
+                .type = const_string },
+            }
+    });
+
+    ecs_entity_t e = ecs_entity(world, {.name = "MyEntity"});
+    test_string_struct *st = (test_string_struct *) ecs_ensure_id(world, e, test_struct);
+    st->value = test_string;
+
+    // we should be able to retrieve the string with a cursor:
+    ecs_meta_cursor_t cursor = ecs_meta_cursor(world, test_struct, st);
+    ecs_meta_push(&cursor);
+    ecs_meta_member(&cursor, "value");
+
+    const char *retrieved_string = ecs_meta_get_string(&cursor);
+
+    test_assert(!ecs_os_strcmp(retrieved_string, test_string));
+
+    // When deleting the entity, Flecs must not try to free the above const string,
+    // otherwise the below will segfault:
+    ecs_delete(world, e);
+
+    test_assert(true);  // If we get to this point without a crash, we're good.
+
+    ecs_fini(world);
+
+}

test/meta/src/main.c

@@ -898,6 +898,7 @@ void OpaqueTypes_deser_entity_from_json(void);
 void OpaqueTypes_ser_deser_world_w_ser_opaque(void);
 void OpaqueTypes_ser_deser_entity(void);
 void OpaqueTypes_ser_deser_0_entity(void);
+void OpaqueTypes_const_string(void);
 
 // Testsuite 'Misc'
 void Misc_primitive_from_stage(void);
@@ -4407,6 +4408,10 @@ bake_test_case OpaqueTypes_testcases[] = {
     {
         "ser_deser_0_entity",
         OpaqueTypes_ser_deser_0_entity
+    },
+    {
+        "const_string",
+        OpaqueTypes_const_string
     }
 };
 
@@ -4705,7 +4710,7 @@ static bake_test_suite suites[] = {
         "OpaqueTypes",
         NULL,
         NULL,
-        17,
+        18,
         OpaqueTypes_testcases
     },
     {