[PATCH] Avoid backtrace from __stack_chk_fail [BZ #12189]

[Florian Weimer]

* H. J. Lu:

>> Would be better to use bool since it is an internal function?
>
> I thought about it.  I wanted to avoid including <stdbool.h> in
> include/stdio.h.  I can add it if it is desirable.

You could use _Bool if that's a concern.