https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108187
--- Comment #3 from Ilya Maximets <i.maximets at ovn dot org> --- (In reply to Ilya Maximets from comment #2) > (In reply to Richard Biener from comment #1) > > Well, between the store to ->source and the read from it is the call > > to dp_packet_use_afxdp which gets &xpacket->packet as argument and thus > > needs to be treated as clobbering ->source. So GCC can indeed not know > > that ->source is DPBUF_AFXDP since the path is not provable impossible. > > dp_packet_use_afxdp doesn't even get a const struct dp_packet * argument > > (not that this would semantically change things in C). > > Hmm, dp_packet_use_afxdp() is the function that sets source to DPBUF_AFXDP > and initializes other parts of the structure. So, it cannot take a const > argument. If GCC just doesn't look inside the dp_packet_use_afxdp() function > at all here, then it will indeed not know that the source is DPBUF_AFXDP now. Clarification: I realized that dp_packet_use_afxdp() is part of a different translation unit, so GCC doesn't have a chance to know what this function is doing, hence it doesn't know that source is DPBUF_AFXDP. Though I don't know how we can change that code to make GCC happy. We'll likely end up just disabling a warning. > However, I'm not sure why the issue doesn't appear with -O0 then. I'm still not sure why this is happening though. Is there something special about -O0 ?
