added container_of macro

Author: Fabrice Bellard

cutils.h

@@ -49,6 +49,9 @@
 #define countof(x) (sizeof(x) / sizeof((x)[0]))
 #endif
 
+/* return the pointer of type 'type *' containing 'ptr' as field 'member' */
+#define container_of(ptr, type, member) ((type *)((uint8_t *)(ptr) - offsetof(type, member)))
+
 typedef int BOOL;
 
 #ifndef FALSE

list.h

@@ -36,8 +36,7 @@ struct list_head {
 #define LIST_HEAD_INIT(el) { &(el), &(el) }
 
 /* return the pointer of type 'type *' containing 'el' as field 'member' */
-#define list_entry(el, type, member) \
-    ((type *)((uint8_t *)(el) - offsetof(type, member)))
+#define list_entry(el, type, member) container_of(el, type, member)
 
 static inline void init_list_head(struct list_head *head)
 {

quickjs.c

@@ -4064,7 +4064,7 @@ void JS_FreeCString(JSContext *ctx, const char *ptr)
     if (!ptr)
         return;
     /* purposely removing constness */
-    p = (JSString *)(void *)(ptr - offsetof(JSString, u));
+    p = container_of(ptr, JSString, u);
     JS_FreeValue(ctx, JS_MKPTR(JS_TAG_STRING, p));
 }