[PATCH] avoid ICE when pretty-printing a VLA with an error bound (PR 85956)

[Jakub Jelinek]

On Thu, May 31, 2018 at 01:34:19PM -0400, Jason Merrill wrote:
> >> Where is the error_mark_node coming from in the first place?
> >
> > remap_type invoked during omp-low.c (scan_omp).
> > omp_copy_decl returns error_mark_node for decls that tree-inline.c wants
> > to remap, but they aren't actually remapped for some reason.
> > For normal VLAs gimplify.c makes sure the needed artifical decls are
> > firstprivatized, but in this case (VLA not in some decl's type, but just
> > referenced indirectly through pointers) nothing scans those unless
> > those temporaries are actually used in the code.
> 
> Returning error_mark_node from omp_copy_decl and then continuing seems
> like the problem, then.  Would it really be that hard to return an
> uninitialized variable instead?

The routine doesn't know if it is used in a context of a VLA bound or
something else, in the former case it is acceptable to swap it for some
other var, but in the latter case it would be just a bug, so using
error_mark_node in that case instead is better to catch those.
I can try to do that in tree-inline.c, but really not sure how hard would it
be.
Or handle it in the gimplifier, scan for such vars and add private clauses
for those, that will mean nothing will be passed around.

	Jakub