"Michael S. Tsirkin" <m...@redhat.com> wrote: > On Wed, Dec 02, 2009 at 08:03:22PM +0100, Juan Quintela wrote: >> "Michael S. Tsirkin" <m...@redhat.com> wrote: >> >> > I don't understand. >> > container_of is just more generic than DO_UPCAST. >> > So why *ever* use DO_UPCAST? Let's get rid of it.
.... >> See how you create a device of size struct_size, but then you access it >> with vdev. If vdev is _not_ the 1st element of the struct, you have got >> corruption. > > A cleaner solution IMO would be to have callers allocate the memory > and pass VirtIODevice * to virtio_common_init. Been there, asked for that. Basically qdev + passing initialized memory = nono >> DO_UPCAST() prevent you for having that error. > > > If we want to assert specific structure layout, this > should be a compile-time check. There's no > reason to do this check every time at a random place where > DO_UPCAST is called. See DO_UPCAST() definition :) It is a compile time check. It just do cpp magic to be sure that things are right. DO_UPCAST() == (cast *) with some typechecking. >> container_of() would have leave you go around, and have a memory >> corruption not easy to fix. >> >> DO_UPCAST() macro was created just to avoid this kind of errors. >> >> Later, Juan.
