Hi, On Thu, Mar 09, 2017 at 12:46:09PM +0100, Christophe de Dinechin wrote: > > > On 8 Mar 2017, at 22:16, Victor Toso <li...@victortoso.com> wrote: > > > > Hi, > > > > On Wed, Mar 08, 2017 at 07:21:15PM +0100, Christophe de Dinechin wrote: > >> I have several errors like this: > >> > >> spice-channel.c:1923:12: error: cast from 'uint8_t *' (aka 'unsigned char > >> *') to > >> 'uint32_t *' (aka 'unsigned int *') increases required alignment from > >> 1 to > >> 4 [-Werror,-Wcast-align] > >> ...(uint32_t *)((uint8_t *)c->peer_msg + > >> GUINT32_FROM_LE(c->peer_msg->caps_offset)); > >> > >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >> > >> Is there any guarantee that the result pointer will be 32-bit aligned? > >> In other words, is it guaranteed that the c->peer_msg->caps_offset > >> will be a multiple of 4? I don’t see this written in the spec. > >> > >> Based on the answer, the correct fix is: > >> > >> - If aligned, to cast to a uint32_t * in a way that disables the warning > >> > >> - If misaligned, to replaced *p with a read operation that is safe when > >> mis-aligned (OS dependent I guess) > > > > Yes, we should check case-by-case. I started doing some work around this > > (nearly one and half year ago already!) but I got stuck on explaining > > the rationale for each cast which would avoid the warnings. > > > > You can see the comments and suggestions at the time are in the > > following thread: > > > > https://lists.freedesktop.org/archives/spice-devel/2015-August/021535.html > > <https://lists.freedesktop.org/archives/spice-devel/2015-August/021535.html> > > Ach, I see you used SPICE_ALIGNED_CAST and SPICE_UNALIGNED_CAST. I > used SPICE_REALIGN_CAST :-( > > Will try to integrate your patches, thanks.
Feel free to take the solution that works best for you based on the comments from Frediano/Christophe there. The hard part is not casting around but properly explaining :-) I'd be super happy if we can build with clang without warnings (excluding vala) :) > > > > > Cheers, > > toso > >> > >> > >> Thanks > >> Christophe > >> > >> _______________________________________________ > >> Spice-devel mailing list > >> Spice-devel@lists.freedesktop.org > >> <mailto:Spice-devel@lists.freedesktop.org> > >> https://lists.freedesktop.org/mailman/listinfo/spice-devel > >> <https://lists.freedesktop.org/mailman/listinfo/spice-devel> > _______________________________________________ > Spice-devel mailing list > Spice-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/spice-devel
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