[Bug middle-end/56474] [4.8 regression] bogus Storage_Error raised for record containing empty zero-based array

["ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56474

--- Comment #14 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2013-03-06 17:19:42 UTC ---
> Note the hacks all boil down to the fact that FEs use signed array
> domains but unsigned sizetype TYPE_DOMAIN.  The C and C++ FE were
> adjusted to use (unsigned) [1, 0] for zero-sized arrays - I believe
> the current hacks are all because of Ada (and yes, I invented them
> to not need to fiddle with the Ada FE when removing TYPE_IS_SIZETYPE).

Exactly, that's my point: all the hacks are there to cope with overflow issues
introduced by the removal of TYPE_IS_SIZETYPE.  Mine is another small one.

> There is still the Ada FE bug I opened that shows that arrays
> with [0, USIZETYPE_MAX] vs. [SSIZETYPE_MIN, SSIZETYPE_MAX] do not
> work.  Independent of any hacks to fix the current error to address
> that you need to work to fix the signedness issue (which may of
> course require middle-end adjustments).

Sure.

> If you don't want overflow you can as well re-set TREE_OVERFLOW
> on the result ... (just to give another option).

That's exactly what the hack at stor-layout.c 2234 does for C and C++!