UBI: eliminate possible undefined behaviour

The assignment to pos when rb is finally NULL is undefined behaviour.
Upon seeing that assignment, GCC may assume that rb is not NULL, and
the loop condition ``rb'' may be optimised away.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 6a5fe963378367ab48f871cbd6893d56d4ed454e..c290f51dd178fc95c8a4b26caf1017309f50d601 100644 (file)
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -579,7 +579,8 @@ void ubi_do_get_volume_info(struct ubi_device *ubi, struct ubi_volume *vol,
        for (rb = rb_first(root),                                            \
             pos = (rb ? container_of(rb, typeof(*pos), member) : NULL);     \
             rb;                                                             \
-            rb = rb_next(rb), pos = container_of(rb, typeof(*pos), member))
+            rb = rb_next(rb),                                               \
+            pos = (rb ? container_of(rb, typeof(*pos), member) : NULL))
 
 /**
  * ubi_zalloc_vid_hdr - allocate a volume identifier header object.