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 Cheers, toso > > > Thanks > Christophe > > _______________________________________________ > Spice-devel mailing list > Spice-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/spice-devel
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