Re: [PATCH] libmlx4: Fix a compiler warning

Bart Van Assche
2012-04-02T15:56:55Z

On 04/01/12 19:09, Bart Van Assche wrote:

> 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 ?

Sorry, but the patch I sent yesterday was wrong. Please replace by 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 | 9 +++++++++
src/verbs.c | 5 +++++
2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/configure.in b/configure.in
index 8aad5ff..eeb4430 100644
--- a/configure.in
+++ b/configure.in
@@ -63,6 +63,15 @@ 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_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <infiniband/verbs.h>]],
+ [[union ibv_gid g; return sizeof(g.u32);]])],
+ [AC_DEFINE([HAVE_IBV_GID_U32],
+ [1],
+ [Define to 1 if ibv_gid has a member called u32.])
+ ])
+
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..b52f799 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_U32
+ 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;