- check_types_match(*(member_ptr), ((containing_type *)0)->member))
+/**
+ * container_of_var - get pointer to enclosing structure using a variable
+ * @member_ptr: pointer to the structure member
+ * @var: a pointer to a structure of same type as this member is within
+ * @member: the name of this member within the structure.
+ *
+ * Given a pointer to a member of a structure, this macro does pointer
+ * subtraction to return the pointer to the enclosing type.
+ *
+ * Example:
+ * struct info
+ * {
+ * int some_other_field;
+ * struct foo my_foo;
+ * };
+ *
+ * struct info *foo_to_info(struct foo *foop)
+ * {
+ * struct info *i = container_of_var(foo, i, my_foo);
+ * return i;
+ * }
+ */
+#ifdef HAVE_TYPEOF
+#define container_of_var(member_ptr, var, member) \
+ container_of(member_ptr, typeof(*var), member)
+#else
+#define container_of_var(member_ptr, var, member) \
+ ((void *)((char *)(member_ptr) - offsetof(containing_type, member)))
+#endif
+
#endif /* CCAN_CONTAINER_OF_H */
--- /dev/null
+#include "container_of/container_of.h"
+#include <stdlib.h>
+
+struct foo {
+ int a;
+ char b;
+};
+
+int main(int argc, char *argv[])
+{
+ struct foo foo = { .a = 1, .b = 2 }, *foop;
+ int *intp = &foo.a;
+
+#ifdef FAIL
+ /* b is a char, but intp is an int * */
+ foop = container_of_var(intp, foop, b);
+#else
+ foop = NULL;
+#endif
+ return intp == NULL;
+}
int *intp = &foo.a;
char *charp = &foo.b;
- plan_tests(2);
+ plan_tests(4);
ok1(container_of(intp, struct foo, a) == &foo);
ok1(container_of(charp, struct foo, b) == &foo);
+ ok1(container_of_var(intp, &foo, a) == &foo);
+ ok1(container_of_var(charp, &foo, b) == &foo);
return exit_status();
}