Re: [PATCH] libmlx4: Fix a compiler warning

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 10/11/11 00:41, Roland Dreier wrote:

> On Mon, Oct 10, 2011 at 10:47 AM, Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org> wrote:
>> -       uint32_t hi = *(uint32_t *)(gid->raw);
>> -       uint32_t lo = *(uint32_t *)(gid->raw + 4);
>> -       if (hi == htonl(0xfe800000) && lo == 0)
>> -               return 1;
>> +       uint32_t hi = gid->u32[0];
>> +       uint32_t lo = gid->u32[1];
> 
> Thanks, however I like to keep libmlx4 backwards compatible
> if possible.  So we can't do this unconditionally.


How about the patch below ?

[PATCH] libmlx4: Fix a compiler warning

Avoid that link_local_gid() triggers the following compiler warning:
dereferencing type-punned pointer will break strict-aliasing rules

Signed-off-by: Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>
---
 configure.in |   10 ++++++++++
 src/verbs.c  |    5 +++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/configure.in b/configure.in
index 8aad5ff..eb03820 100644
--- a/configure.in
+++ b/configure.in
@@ -63,6 +63,16 @@ AM_CONDITIONAL(HAVE_IBV_DEVICE_LIBRARY_EXTENSION,
     test $IBV_DEVICE_LIBRARY_EXTENSION != IBV_DEVICE_LIBRARY_EXTENSION)
 AC_SUBST(IBV_DEVICE_LIBRARY_EXTENSION)
 
+# Check whether ibv_gid has a member called u32.
+
+AC_CHECK_MEMBER([ibv_gid.u32],
+	        [AC_DEFINE([HAVE_IBV_GID_U32],
+		           1,                                   
+			   [Define to 1 if ibv_gid has a member called u32.])
+                ],
+		[],
+		[#include <infiniband/verbs.h>])
+
 AC_CACHE_CHECK(whether ld accepts --version-script, ac_cv_version_script,
     [if test -n "`$LD --help < /dev/null 2>/dev/null | grep version-script`"; then
         ac_cv_version_script=yes
diff --git a/src/verbs.c b/src/verbs.c
index 408fc6d..c7a08a5 100644
--- a/src/verbs.c
+++ b/src/verbs.c
@@ -624,8 +624,13 @@ int mlx4_destroy_qp(struct ibv_qp *ibqp)
 
 static int link_local_gid(const union ibv_gid *gid)
 {
+#ifdef HAVE_IBV_GID_M32
+	uint32_t hi = gid->u32[0];
+	uint32_t lo = gid->u32[1];
+#else
 	uint32_t hi = *(uint32_t *)(gid->raw);
 	uint32_t lo = *(uint32_t *)(gid->raw + 4);
+#endif
 	if (hi == htonl(0xfe800000) && lo == 0)
 		return 1;
 
-- 
1.7.7


--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html