http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46488
--- Comment #25 from Joe Orton <jorton at redhat dot com> 2010-11-29 14:03:40 UTC --- (In reply to comment #22) > APR_RING_SPLICE_HEAD does such a dereference as far I can see: You are right, sorry, I had forgotten exactly how this code works. (In reply to comment #24) > not really. But using > > typedef struct elem elem_ __attribute__((may_alias)); > #define APR_RING_SENTINEL(hp, elem, link) \ > (struct elem_ *)((char *)(hp) - APR_OFFSETOF(struct elem, link)) > > would be safe wrt strict aliasing (if the pointer is only dereferenced > directly and not casted to another pointer type before, of course). I don't think we can guarantee this with the API unchanged; the sentinel pointer could well be stored in a "struct elem *" pointer.