diff --git a/cutils.h b/cutils.h
index 31f7cd8..8399d61 100644
--- a/cutils.h
+++ b/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
diff --git a/list.h b/list.h
index 0a1bc5a..5c18234 100644
--- a/list.h
+++ b/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)
 {
diff --git a/quickjs.c b/quickjs.c
index 2e391e5..45b0be8 100644
--- a/quickjs.c
+++ b/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));
 }