From: Phil Carmody <ext-phil.2.carmody@nokia.com>
Date: Thu, 23 Jul 2009 13:29:10 +0000 (+0200)
Subject: UBI: eliminate possible undefined behaviour
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=758d8e46347aee199e7025b8c571bab75d2de63f;p=deliverable%2Flinux.git

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 6a5fe9633783..c290f51dd178 100644
--- 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.