Re: [PATCH] x86/vhpet: Fix type size in timer_int_route_valid

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 31/07/2020 10:53, Jan Beulich wrote:
> On 31.07.2020 10:38, Eslam Elnikety wrote:
> > On 28.07.20 19:51, Jan Beulich wrote:
> > > On 28.07.2020 11:26, Andrew Cooper wrote:
> > > > --- a/xen/include/asm-x86/hvm/vpt.h
> > > > +++ b/xen/include/asm-x86/hvm/vpt.h
> > > > @@ -73,7 +73,13 @@ struct hpet_registers {
> > > >        uint64_t isr;               /* interrupt status reg */
> > > >        uint64_t mc64;              /* main counter */
> > > >        struct {                    /* timers */
> > > > -        uint64_t config;        /* configuration/cap */
> > > > +        union {
> > > > +            uint64_t config;    /* configuration/cap */
> > > > +            struct {
> > > > +                uint32_t _;
> > > > +                uint32_t route;
> > > > +            };
> > > > +        };
> > > So long as there are no static initializers for this construct
> > > that would then suffer the old-gcc problem, this is of course a
> > > fine arrangement to make.
> > I have to admit that I have no clue what the "old-gcc" problem is. I am
> > curious, and I would appreciate pointers to figure out if/how to
> > resolve. Is that an old, existing problem? Or a problem that was present
> > in older versions of gcc?
> Well, as already said - the problem is with old gcc not dealing
> well with initializers of structs/unions with unnamed fields.
You seem to know quite well the problem. So would you mind to give us 
more details on which GCC version is believed to be broken?
> > If the latter, is that a gcc version that we still care about?
> Until someone makes a (justified) proposal what the new minimum
> version(s) ought to be, I'm afraid we still have to care. This
> topic came up very recently in another context, and I've proposed
> to put it on the agenda of the next community call.
I don't think Eslam was requesting to change the limits. He was just 
asking whether one of the compiler we support is affected.
Cheers,


--
Julien Grall