From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH rdma-core 2/2] mlx5: Convert explicitly to signed char Date: Wed, 30 Aug 2017 11:49:03 -0600 Message-ID: <20170830174903.GA13474@obsidianresearch.com> References: <1504102764-21638-1-git-send-email-yishaih@mellanox.com> <1504102764-21638-3-git-send-email-yishaih@mellanox.com> <20170830164952.GA9310@obsidianresearch.com> <20170830174402.GC10539@mtr-leonro.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170830174402.GC10539-U/DQcQFIOTAAJjI8aNfphQ@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Leon Romanovsky Cc: Yishai Hadas , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, majd-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Wed, Aug 30, 2017 at 08:44:02PM +0300, Leon Romanovsky wrote: > On Wed, Aug 30, 2017 at 10:49:52AM -0600, Jason Gunthorpe wrote: > > On Wed, Aug 30, 2017 at 05:19:24PM +0300, Yishai Hadas wrote: > > > From: Leon Romanovsky > > > > > > The 0x80 value is a canonical way to mark as not-used in intrinsics > > > function calls. > > > > This commit message is not good, try: > > > > _mm_shuffle_epi8 requires 0x80 to set the output byte to zero, but > > _mm_set_epi8() accepts char. If gcc is compiling in a configuration > > with a signed char then it can produce a -Werror=overflow warning. > > > > And this fix is wrong, since it just moves the warning to > > configurations that have an unsigned char. (eg -funsigned-char) > > I have gut feeling that with such option "-funsigned-char" half of the > world will break. Nope, some arches default to it on. aarch64 for instance. This is why we have uint8_t, and using 'char' for anything other than a string character is very wrong. Jason -- 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