[PATCH 2/8] lib/ext2fs/rbtree.h: Fix container_of() undefined behavior

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

The code before the macro definition #undefs and redefines offsetof().
Unfortunately the new definition actually causes undefined behavior.

The code checks for __compiler_offsetof() before redefining. However
I'm not sure where it is supposed to be defined.

Just enclose the redefinition in #ifndef __GNUC__ for now.

Caught using clang -fsanitize=undefined.

Signed-off-by: Sami Liedes <sami.liedes@iki.fi>
---
 lib/ext2fs/rbtree.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/ext2fs/rbtree.h b/lib/ext2fs/rbtree.h
index 16defb5..088c352 100644
--- a/lib/ext2fs/rbtree.h
+++ b/lib/ext2fs/rbtree.h
@@ -96,12 +96,14 @@ static inline struct page * rb_insert_page_cache(struct inode * inode,
 
 #include <stdlib.h>
 
+#ifndef __GNUC__
 #undef offsetof
 #ifdef __compiler_offsetof
 #define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER)
 #else
 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
 #endif
+#endif
 
 #define container_of(ptr, type, member) ({			\
 	const __typeof__( ((type *)0)->member ) *__mptr = (ptr);	\
-- 
1.7.10.4