On Sat, Feb 06, 2016 at 08:36:27PM +0000, Bernd Edlinger wrote:
>
> Hi Jakub,
>
> as a follow-up for your c/69669 fix, I'd like to have the enum mode also
> honored
> in C++ code, because the mode attribute now finally really works in C, but it
> is
> completely and silently(!) ignored by C++ code, which results in incompatible
> code.
>
> So I duplicated what is done in c/c-decl.c also in cp/decl.c. That worked
> immediately, except that it is not possible to explicitly check the "mode"
> attribute in the TYPE_ATTRIBUTES (enumtype) because that attribute
> is never copied to the type, and the original attribute list is not available
> here. That should be OK, as this check was added to fix pr52085 which
> does not apply here, because C++ does not support enum forward
> declarations.
it is allowed if you do something like
enum X : int;
but it seems really pointless to support setting the size of something
when the language gives you a standard way to do that.
> If that patch is not appropriate for stage 4, I would at least want to emit
> an attribute directive ignored warning in c++ mode. I think that could
> be done in handle_mode_attribute. But fixing that feature is cooler.
Its definitely bad to sighlently ignore the attribute. On one hand
being compatable with C seems nice, but on the other hand in C++ 11 and
later you can set the size without using attributes, and the mode thing
has always seemed a bit odd to me since its not really clear what C
type they corespond to.
Trev
>
> Boot-strapped and regression tested on x86_64-pc-linux-gnu.
> Ok for trunk?
>
>
> Thanks
> Bernd.
> cp:
> 2016-02-06 Bernd Edlinger <bernd.edlin...@hotmail.de>
>
> * decl.c (finish_enum_value_list): Use the specified mode.
>
> testsuite:
> 2016-02-06 Bernd Edlinger <bernd.edlin...@hotmail.de>
>
> * c-c++-common/pr69669.c: Check the used mode.
> Index: gcc/cp/decl.c
> ===================================================================
> --- gcc/cp/decl.c (Revision 233176)
> +++ gcc/cp/decl.c (Arbeitskopie)
> @@ -13310,6 +13310,19 @@ finish_enum_value_list (tree enumtype)
> use_short_enum = flag_short_enums
> || lookup_attribute ("packed", TYPE_ATTRIBUTES (enumtype));
>
> + /* If the precision of the type was specified with an attribute and it
> + was too small, give an error. Otherwise, use it. */
> + if (TYPE_PRECISION (enumtype))
> + {
> + if (precision > TYPE_PRECISION (enumtype))
> + error ("specified mode too small for enumeral values");
> + else
> + {
> + use_short_enum = true;
> + precision = TYPE_PRECISION (enumtype);
> + }
> + }
> +
> for (itk = (use_short_enum ? itk_char : itk_int);
> itk != itk_none;
> itk++)
> Index: gcc/testsuite/c-c++-common/pr69669.c
> ===================================================================
> --- gcc/testsuite/c-c++-common/pr69669.c (Revision 233176)
> +++ gcc/testsuite/c-c++-common/pr69669.c (Arbeitskopie)
> @@ -1,5 +1,6 @@
> /* PR c/69669 */
> /* { dg-do compile } */
> +/* { dg-options "-fdump-rtl-final" } */
>
> enum __attribute__((mode(QI))) E { F = 1 };
>
> @@ -8,3 +9,5 @@ foo (enum E *x, int y)
> {
> *x = (enum E) y;
> }
> +
> +/* { dg-final { scan-rtl-dump-times "mem:QI" 1 "final" } } */
