add nil entity macros

src/common.h

@@ -161,8 +161,9 @@ extern "C" {
 #define INTERNAL static
 #define GLOBAL static
 
+/* Storage specifiers */
 #pragma section(".roglob", read)
-#define READONLY __declspec(allocate(".roglob"))
+#define READ_ONLY __declspec(allocate(".roglob"))
 
 /* Markup */
 #define UNUSED void
@@ -238,6 +239,19 @@ extern "C" {
 #define CAT1(a, b) a ## b
 #define CAT(a, b) CAT1(a, b)
 
+/* ========================== *
+ * Nil structs
+ * ========================== */
+
+/* Declare */
+#define DECLARE_NIL_STRUCT(type, function_name) \
+    extern READ_ONLY type CAT(__nil_struct__, function_name); \
+    INLINE READ_ONLY type *function_name(void) { return &CAT(__nil_struct__, function_name); }
+
+/* Expects struct body after invocation. E.g. DEFINE_NIL_STRUCT(struct a, a_nil) { 0 } */
+#define DEFINE_NIL_STRUCT(type, function_name) \
+    type READ_ONLY CAT(__nil_struct__, function_name)
+
 #if 0
 /* ========================== *
  * Bit utils
@@ -412,12 +426,10 @@ struct v4_array {
 };
 
 struct xform {
-    struct {
     struct v2 bx;  /* X basis vector (x axis) */
     struct v2 by;  /* Y basis vector (y axis)*/
     struct v2 og;  /* Translation vector (origin) */
 };
-};
 
 struct mat4x4 {
     f32 e[4][4];

src/entity.c

@@ -1,6 +1,6 @@
 #include "entity.h"
 
-READONLY struct entity _g_entity_nil = { 0 };
+DEFINE_NIL_STRUCT(struct entity, entity_nil) = { 0 };
 
 /* ========================== *
  * Prop

src/entity.h

@@ -96,14 +96,7 @@ struct entity {
     f32 camera_zoom;
 };
 
-/* Nil entity */
+DECLARE_NIL_STRUCT(struct entity, entity_nil)
-
-extern READONLY struct entity _g_entity_nil;
-
-INLINE READONLY struct entity *entity_nil(void)
-{
-    return &_g_entity_nil;
-}
 
 /* Prop */