http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49140
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-05-24 14:53:29 UTC --- stack_init computes &pari_tree - &s_node which is undefined, stack_alloc then re-computes one via stack_base. That's broken as well. Not sure if this eventually causes the issue, but certainly the code is full of C implementation details that you can't capture in standard C.
