http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48973
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-05-12 07:36:07 UTC --- And even more reduced: extern void abort (void); struct S { int f : 1; } s; int v = -1; int main () { s.f = (v & 1) > 0; if ((unsigned int) s.f != -1U) abort (); return 0; }