diff --git a/core/class.c b/core/class.c
index 6d5942a..550a2ed 100644
--- a/core/class.c
+++ b/core/class.c
@@ -28,7 +28,7 @@ const char *b_class_get_name(const struct _b_class *c)
 	return c->c_type->r_info->t_name;
 }
 
-void *b_class_get_interface(const struct _b_class *c, const union b_type *id)
+void *b_class_get_interface(const struct _b_class *c, const union b_type_id *id)
 {
 	if (!c) {
 		return NULL;
diff --git a/core/include/blue/core/encoding.h b/core/include/blue/core/encoding.h
index 50c3f90..e1b80ed 100644
--- a/core/include/blue/core/encoding.h
+++ b/core/include/blue/core/encoding.h
@@ -5,6 +5,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+B_DECLS_BEGIN;
+
 #define B_WCHAR_INVALID ((b_wchar) - 1)
 
 typedef int32_t b_wchar;
@@ -38,4 +40,6 @@ BLUE_API size_t b_wchar_utf8_codepoint_count(const char *s, size_t nr_bytes);
 BLUE_API size_t b_wchar_utf8_string_encoded_size(
 	const b_wchar *s, size_t nr_codepoints);
 
+B_DECLS_END;
+
 #endif
diff --git a/core/include/blue/core/macros.h b/core/include/blue/core/macros.h
index 5f426d0..3f33857 100644
--- a/core/include/blue/core/macros.h
+++ b/core/include/blue/core/macros.h
@@ -2,6 +2,7 @@
 #define BLUE_CORE_MACROS_H_
 
 #include <blue/core/class.h>
+#include <blue/core/misc.h>
 #include <blue/core/object.h>
 #include <blue/core/thread.h>
 #include <blue/core/type.h>
@@ -10,6 +11,8 @@
 #define __B_IFACE_I0(p, x) p##x
 #define __B_IFACE_I1(p, x) __B_IFACE_I0(p, x)
 
+#define B_STRUCT_EMPTY     char _x
+
 /* Type definitions macros (for use in .c source file) */
 
 #define B_TYPE_CLASS_DEFINITION_BEGIN(type_name)                               \
@@ -186,12 +189,4 @@
 		func_name(priv);                                               \
 	} while (0)
 
-#ifdef __cplusplus
-#define B_DECLS_BEGIN extern "C" {
-#define B_DECLS_END   }
-#else
-#define B_DECLS_BEGIN
-#define B_DECLS_END
-#endif
-
 #endif
diff --git a/core/include/blue/core/misc.h b/core/include/blue/core/misc.h
index 3e06ddf..bbd08c2 100644
--- a/core/include/blue/core/misc.h
+++ b/core/include/blue/core/misc.h
@@ -8,6 +8,14 @@
 #define _Nonnull
 #endif
 
+#ifdef __cplusplus
+#define B_DECLS_BEGIN extern "C" {
+#define B_DECLS_END   }
+#else
+#define B_DECLS_BEGIN
+#define B_DECLS_END
+#endif
+
 #define B_NPOS            ((size_t)-1)
 
 #define b_min(type, x, y) (z__b_min_##type(x, y))
diff --git a/core/include/blue/core/object.h b/core/include/blue/core/object.h
index 3063420..9a8bfb3 100644
--- a/core/include/blue/core/object.h
+++ b/core/include/blue/core/object.h
@@ -4,6 +4,8 @@
 #include <blue/core/misc.h>
 #include <blue/core/type.h>
 
+B_DECLS_BEGIN;
+
 #define B_OBJECT_MAGIC      0xDECAFC0C0ABEEF13ULL
 
 #define B_OBJECT(p)         ((b_object *)(p))
@@ -36,4 +38,6 @@ BLUE_API b_object *b_object_create(b_type type);
 BLUE_API void b_object_to_string(const b_object *p, B_TYPE_FWDREF(b_stream) * out);
 BLUE_API bool b_object_is_type(const b_object *p, b_type type);
 
+B_DECLS_END;
+
 #endif
diff --git a/core/include/blue/core/stream.h b/core/include/blue/core/stream.h
index a77f80b..5e194db 100644
--- a/core/include/blue/core/stream.h
+++ b/core/include/blue/core/stream.h
@@ -48,6 +48,7 @@ B_TYPE_CLASS_DECLARATION_BEGIN(b_stream)
 B_TYPE_CLASS_DECLARATION_END(b_stream)
 
 B_TYPE_CLASS_DECLARATION_BEGIN(b_stream_buffer)
+	B_STRUCT_EMPTY;
 B_TYPE_CLASS_DECLARATION_END(b_stream_buffer)
 
 BLUE_API b_type b_stream_get_type();
diff --git a/core/include/blue/core/stringstream.h b/core/include/blue/core/stringstream.h
index 18e9b7e..74f34f3 100644
--- a/core/include/blue/core/stringstream.h
+++ b/core/include/blue/core/stringstream.h
@@ -14,6 +14,7 @@ B_DECLS_BEGIN;
 B_DECLARE_TYPE(b_stringstream);
 
 B_TYPE_CLASS_DECLARATION_BEGIN(b_stringstream)
+	B_STRUCT_EMPTY;
 B_TYPE_CLASS_DECLARATION_END(b_stringstream)
 
 BLUE_API b_type b_stringstream_get_type(void);
diff --git a/core/include/blue/core/type.h b/core/include/blue/core/type.h
index b486b9e..dc952c5 100644
--- a/core/include/blue/core/type.h
+++ b/core/include/blue/core/type.h
@@ -7,6 +7,8 @@
 #include <stdint.h>
 #include <string.h>
 
+B_DECLS_BEGIN;
+
 #define B_TYPE_MAX_INTERFACES 64
 
 struct _b_class;
@@ -16,7 +18,7 @@ typedef void (*b_class_init_function)(struct _b_class *, void *);
 typedef void (*b_instance_init_function)(struct _b_object *, void *);
 typedef void (*b_instance_fini_function)(struct _b_object *, void *);
 
-typedef const union b_type {
+typedef const union b_type_id {
 	struct {
 		uint64_t p00, p01;
 	} a;
@@ -29,11 +31,11 @@ typedef enum b_type_flags {
 } b_type_flags;
 
 typedef struct b_type_info {
-	union b_type t_id;
-	union b_type t_parent_id;
+	union b_type_id t_id;
+	union b_type_id t_parent_id;
 	const char *t_name;
 	b_type_flags t_flags;
-	union b_type t_interfaces[B_TYPE_MAX_INTERFACES];
+	union b_type_id t_interfaces[B_TYPE_MAX_INTERFACES];
 	size_t t_nr_interfaces;
 	size_t t_class_size;
 	b_class_init_function t_class_init;
@@ -44,9 +46,9 @@ typedef struct b_type_info {
 } b_type_info;
 
 BLUE_API void b_type_id_init(
-	union b_type *out, uint32_t a, uint16_t b, uint16_t c, uint16_t d,
+	union b_type_id *out, uint32_t a, uint16_t b, uint16_t c, uint16_t d,
 	uint64_t e);
-static inline void b_type_id_copy(b_type src, union b_type *dest)
+static inline void b_type_id_copy(b_type src, union b_type_id *dest)
 {
 	dest->a.p00 = src->a.p00;
 	dest->a.p01 = src->a.p01;
@@ -58,9 +60,11 @@ static inline int b_type_id_compare(b_type a, b_type b)
 		return 0;
 	}
 
-	return memcmp(a, b, sizeof(union b_type));
+	return memcmp(a, b, sizeof(union b_type_id));
 }
 
 BLUE_API b_result b_type_register(b_type_info *info);
 
+B_DECLS_END;
+
 #endif
diff --git a/core/type.c b/core/type.c
index 99b6aaf..0c395de 100644
--- a/core/type.c
+++ b/core/type.c
@@ -12,7 +12,7 @@
 #include <string.h>
 
 static struct b_btree type_list = B_BTREE_INIT;
-static union b_type zero_id = {0};
+static union b_type_id zero_id = {0};
 
 struct type_init_ctx {
 	size_t ctx_class_offset;
@@ -39,7 +39,7 @@ B_BTREE_DEFINE_INSERT(
 	put_type_component, component_compare)
 
 static struct b_type_registration *get_type(
-	const b_btree *tree, const union b_type *key)
+	const b_btree *tree, const union b_type_id *key)
 {
 	b_btree_node *cur = tree->b_root;
 	while (cur) {
@@ -60,7 +60,7 @@ static struct b_type_registration *get_type(
 }
 
 struct b_type_component *b_type_get_component(
-	const b_btree *tree, const union b_type *key)
+	const b_btree *tree, const union b_type_id *key)
 {
 	b_btree_node *cur = tree->b_root;
 	while (cur) {
@@ -96,7 +96,7 @@ static struct b_type_component *create_type_component(
 }
 
 void b_type_id_init(
-	union b_type *out, uint32_t a, uint16_t b, uint16_t c, uint16_t d,
+	union b_type_id *out, uint32_t a, uint16_t b, uint16_t c, uint16_t d,
 	uint64_t e)
 {
 	b_i32 x_a = b_i32_htob(a);
@@ -157,7 +157,7 @@ static b_result locate_interface(
 }
 
 static b_result locate_interfaces(
-	const union b_type *interfaces, size_t nr_interfaces,
+	const union b_type_id *interfaces, size_t nr_interfaces,
 	struct b_type_registration *dest, struct type_init_ctx *init_ctx)
 {
 	b_result result = B_RESULT_SUCCESS;
diff --git a/core/type.h b/core/type.h
index c728bdb..efdc549 100644
--- a/core/type.h
+++ b/core/type.h
@@ -35,6 +35,6 @@ struct b_type_registration {
 
 extern struct b_type_registration *b_type_get_registration(b_type id);
 extern struct b_type_component *b_type_get_component(
-	const b_btree *tree, const union b_type *key);
+	const b_btree *tree, const union b_type_id *key);
 
 #endif