[PATCH 1/8] lib/blkid/list.h: Fix undefined behavior in list_entry() macro

[Sami Liedes <sami.liedes@iki.fi>]

Update list_entry() macro, which is basically the same as the
container_of() macro in the kernel, to use offsetof() to fix undefined
behavior.

Caught using clang -fsanitize=undefined.

Signed-off-by: Sami Liedes <sami.liedes@iki.fi>
---
 lib/blkid/list.h |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/blkid/list.h b/lib/blkid/list.h
index c1cbfec..d15228e 100644
--- a/lib/blkid/list.h
+++ b/lib/blkid/list.h
@@ -148,8 +148,9 @@ _INLINE_ void list_splice(struct list_head *list, struct list_head *head)
  * @type:	the type of the struct this is embedded in.
  * @member:	the name of the list_struct within the struct.
  */
-#define list_entry(ptr, type, member) \
-	((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
+#define list_entry(ptr, type, member) ({		       \
+	const typeof( ((type *)0)->member ) *__mptr = (ptr);   \
+	(type *)( (char *)__mptr - offsetof(type,member) );})
 
 /**
  * list_for_each - iterate over elements in a list
-- 
1.7.10.4