[PATCH][Preprocessor]patch to fix PR 90581

[Richard Biener]

On Thu, May 30, 2019 at 10:46 PM David Malcolm <dmalcolm@redhat.com> wrote:
>
> On Thu, 2019-05-30 at 11:23 -0500, Qing Zhao wrote:
> > Hi,
> >
> > PR 90581 (provide an option to adjust the maximum depth of nested
> > #include)
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90581
> >
> > is to add a new cpp option -fmax-inlcude-depth to set the maximum
> > depth of nested #include.
> >
> > '-fmax-include-depth=DEPTH'
> >      Set the maximum depth of the nested include.  The default value
> > is
> >      200.
> >
> > Please check the attached patch.
> > I have done bootstrap and regression test on X86, no any issue.
> >
> > thanks a lot.
> >
> > Qing.
> >
> Thanks for working on this.  It's looking promising, but I agree that a
> param would be better than an option.

Not sure - this is for language limits and we do have existing
like -ftemplate-backtrace-limit and -ftemplate-depth.

> One idea that occurred to me looking at the patch...
>
> > index 3ee8bc4..480c282 100644
> > --- a/libcpp/directives.c
> > +++ b/libcpp/directives.c
> > @@ -831,7 +831,7 @@ do_include_common (cpp_reader *pfile, enum include_type type)
> >      }
> >
> >    /* Prevent #include recursion.  */
> > -  if (pfile->line_table->depth >= CPP_STACK_MAX)
> > +  if (pfile->line_table->depth >= CPP_OPTION (pfile, max_include_depth))
> >      cpp_error (pfile, CPP_DL_ERROR, "#include nested too deeply");
>
> ...a nice usability tweak here would be to give a hint about the new
> param, to give the user an idea on how to increase the limit.
>
> Maybe something like:
>
> cpp_error (pfile, CPP_DL_ERROR,
>           "%<#include%> nested too deeply (depth %i);"
>           " use %<--param max-include-depth=LIMIT%> to support deeper nesting",
>           pfile->line_table->depth);
>
> (though probably that would be better as a followup "note")
>
> Dave