Get rid of infinite recursion for 'typedef' used with GTY-marked 'gcc/diagnostic-spec.h:nowarn_map' [PR101204] (was: [PATCH 1/13] v2 [PATCH 1/13] Add support for per-location warning groups (PR 74765))

[Richard Biener]

On Tue, Nov 9, 2021 at 11:28 AM Thomas Schwinge <thomas@codesourcery.com> wrote:
>
> Hi!
>
> On 2021-09-01T18:14:46-0600, Martin Sebor <msebor@gmail.com> wrote:
> > On 9/1/21 1:35 PM, Thomas Schwinge wrote:
> >> On 2021-06-23T13:47:08-0600, Martin Sebor via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> >>> --- /dev/null
> >>> +++ b/gcc/diagnostic-spec.h
> >>
> >>> +typedef location_t key_type_t;
> >>> +typedef int_hash <key_type_t, 0, UINT_MAX> xint_hash_t;
> >>> +typedef hash_map<xint_hash_t, nowarn_spec_t> xint_hash_map_t;
> >>> +
> >>> +/* A mapping from the location of an expression to the warning spec
> >>> +   set for it.  */
> >>> +extern GTY(()) xint_hash_map_t *nowarn_map;
>
> >> Oh, and one of [my pending changes] actually (unintentially so) happens to resolve
> >> <https://gcc.gnu.org/PR101204> "[12 Regression] infinite recursion in
> >> gtype-desc.c since r12-1801-g7036e9ef462fde8181bece4ac4e03f3aa27204dc",
> >> so unless you've done any work on that, may I take over that PR?
> >
> > I haven't.  Thanks for offering to take it on!  I'm curious to
> > hear how your change fixes that problem.
>
> So, instead of my earlier drive-by fix, I've since distilled what it
> actually is that is causing/fixing this (strange...) problem.  OK to push
> the attached "Get rid of infinite recursion for 'typedef' used with
> GTY-marked 'gcc/diagnostic-spec.h:nowarn_map' [PR101204]"?  (This, of
> course, only fixes the symptom but not the actual underlying problem.
> But I'm not going to dig deep into 'gengtype' at this time.)  ;-)

Did you try if

 typedef hash_map<int_hash<location_t, 0, UINT_MAX>, nowarn_spec_t>
xint_hash_map_t;

works?  Usually a typedef is needed so that gengtype can grok struct
members but it
might very well be confused about two levels of typedefs here?

That said ... I guess this kind of fix is OK - but can you please put
a big fat comment
about this in the actual code and open a bugreport tracking this
gengtype defect?

Thanks,
Richard.

>
> Grüße
>  Thomas
>
>
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