Re: ICE during bootstrap with --enable-checking

["Martin v. Loewis" <martin at loewis dot home dot cs dot tu-berlin dot de>]

> P.S. Here's the preprocessed file and the compiler messages again:

Thanks. I have now confirmed that it happens only if gc,gcac are also
specified; this kind of proves my point that it is a GC
problem. Thanks for reporting it.

I think this is quite difficult to solve: To have the elements in the
bison stack as GC roots, you have to know which of those are
<ttype>. Finding out that by-itself is not that difficult; correlating
it with the state stack is. Essentially, you have to know y.output to
know which semantic values are on the stack in which state. I don't
think bison provides that kind of information at run-time.

Of course, there is a work-around: In SAVE_WARN_FLAGS, mark $$ as ggc
root; in RESTORE_WARN_FLAGS, delete the GC root again. However, I
would not like this at all.

Regards,
Martin