On Wed, Jun 17, 2015 at 12:10 AM, Jan Hubicka <[email protected]> wrote:
>> >> PR middle-end/66325
>> >> * c-decl.c (start_enum): Set TYPE_PACKED consistently among type
>> >> variants.
>> >> Index: c-decl.c
>> >> ===================================================================
>> >> --- c-decl.c (revision 224250)
>> >> +++ c-decl.c (working copy)
>> >> @@ -7946,7 +7946,8 @@
>> >> the_enum->enum_overflow = 0;
>> >>
>> >> if (flag_short_enums)
>> >> - TYPE_PACKED (enumtype) = 1;
>> >> + for (tree v = TYPE_MAIN_VARIANT (enumtype); v ;v = TYPE_NEXT_VARIANT
>> >> (v))
>>
>> Though I wonder why flag_short_enums was not true when building the
>> (main-)variant?
>
> What I believe happens is that there is forward declaration of enum that leads
> to biuld incomplete enum type that has no packed flag set. Then we produce
> a type variant and after that we complete the main variant, but do not update
> the other variant.
>
> Actually looking into where the variant is updated, it happens in finish_enum
> that copies many flags, perhaps it would make more sense to copy TYPE_PACKED
> there?
Yes, it sounds like so.
>> Looks like -fshort-enums is also 'Optimization', so the above is bogus for
>>
>> enum foo {x = 1 };
>>
>> void __attribute__((optimize(short-enums))) foo()
>> {
>> const enum foo x = 1;
>> }
>>
>> no? The main variant is correctly _not_ packed but now you make it
>> packed as you reach foo ()?
>
> Perhaps it is defined as Optimization but it does not bind to uses of types:
>
> enum foo {a,b,c};
> __attribute__((optimize("short-enums")))
> main()
> {
> const enum foo x;
> enum bar {a,b,c};
> printf ("%i %i\n",sizeof (x), sizeof(enum bar));
> }
>
> prints
> 4 1
>
> it depends when the main variant is finished. I wonder if there is any
> practical value on support Optimization attribute for this kind of ABI
> breaking
> options. It may be easier to simply drop the Optimization flag completely
> from
> -fshort-enums and friends.
>
> -fshort-double ICEs at initialization time at least since 4.8.x
> $ gcc t.c -fshort-double
> <built-in>: internal compiler error: in layout_type, at stor-layout.c:2220
> 0xafe41b layout_type(tree_node*)
> ../../gcc/stor-layout.c:2219
>
> so I suggest dropping that flag completely.
IIRC it "works" for -m32, but yes...
Yes also to _not_ make ABI changing flags 'Optimization'.
Richard.
> Honza
>>
>> Richard.
>>
>> > Please fix the formatting here: no space before ;.
>> >
>> > Ok with that change.
>> >
>> > Marek
