On Wed, May 29, 2013 at 03:41:09PM +0200, Paolo Bonzini wrote: > Il 29/05/2013 15:24, Michael S. Tsirkin ha scritto: > > You expect a compiler to pad this structure: > > > > struct foo { > > uint8_t a; > > uint8_t b; > > uint16_t c; > > uint32_t d; > > }; > > > > I'm guessing any compiler that decides to waste memory in this way > > will quickly get dropped by users and then we won't worry > > about building QEMU with it. > > You know the virtio-pci config structures are padded, but not all of > them are. For example, virtio_balloon_stat is not padded and indeed has > an __attribute__((__packed__)) in the spec. > > For this reason I prefer to have the attribute everywhere. So people > don't have to wonder why it's here and not there. > > Paolo BTW we don't even do this consistently everywhere in QEMU. It would have been better to have a rule to avoid packed as much as possible, then we'd have found the misaligned field bug in balloon before it's too late. That would be a good rule to adopt I think: any pack if something is misaligned, and document the reason. -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization