sizeof (struct tYpO *) : it is just a typo or rather a bug ?

["Toralf Förster" <toralf.foerster@gmx.de>]

Inspired by this "typo" fix 
http://article.gmane.org/gmane.linux.kernel/1754640
I grep'ed the current git tree of linus for similar issues.

For these 4 places I'm wondering where the appropriate struct definition is located :

arch/ia64/sn/kernel/io_acpi_init.c:         sizeof(struct pci_devdev_info *)) {
tools/perf/builtin-sched.c:     sched->tasks = realloc(sched->tasks, sched->nr_tasks * sizeof(struct task_task *));
fs/ceph/xattr.c:                xattrs = kcalloc(numattr, sizeof(struct ceph_xattr *),
fs/ceph/xattr.c:                memset(xattrs, 0, numattr*sizeof(struct ceph_xattr *));

Nevertheless I was told, that gcc doesn't complain about such things due to eventually evaluating it to "sizeof(null)". I'm however curious if at least a warning should be emitted in such a case, or?

-- 
Toralf