On 12/21/21 12:01, Dumitru Ceara wrote:
UB Sanitizer was flagging OBJECT_CONTAINING() as undefined behavior
due to the way it's used when iterating through collections, e.g.,
HMAP_FOR_EACH_INIT(). However, in such cases we don't actually
dereference the pointer, we just use its value. Avoid the undefined
behavior by casting to 'void *' first.
Signed-off-by: Dumitru Ceara <[email protected]>
---
include/openvswitch/util.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/openvswitch/util.h b/include/openvswitch/util.h
index 228b185c3a5f..cfbd5f1a3375 100644
--- a/include/openvswitch/util.h
+++ b/include/openvswitch/util.h
@@ -128,7 +128,7 @@ OVS_NO_RETURN void ovs_assert_failure(const char *, const
char *, const char *);
* from the type of '*OBJECT'. */
#define OBJECT_CONTAINING(POINTER, OBJECT, MEMBER) \
((OVS_TYPEOF(OBJECT)) (void *) \
- ((char *) (POINTER) - OBJECT_OFFSETOF(OBJECT, MEMBER)))
+ ((uintptr_t)(void *)(POINTER) - OBJECT_OFFSETOF(OBJECT, MEMBER)))
/* Given POINTER, the address of the given MEMBER within an object of the type
* that that OBJECT points to, assigns the address of the outer object to
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I've been looking into UB recently and I agree: moving from pointer to integer
arithmetics _can_ relax some restrictions that the compiler enforces on
pointers, so the patch looks good to me.
There are more pointer arithmetics that can be replaced with "uintptr_t" in
util.h. Do you plan to replace all of them? If not, I can do it in a series I'm
preparing that also addresses UB on this macros.
--
Adrián Moreno
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