Re: [Xen-devel] [PATCH v2 01/16] xen/mm: Don't use _{g, m}fn for defining INVALID_{G, M}FN

[Tim Deegan <tim@xxxxxxx>]

At 01:32 -0600 on 20 Jun (1497922345), Jan Beulich wrote:
> >>> On 19.06.17 at 18:57, <julien.grall@xxxxxxx> wrote:
> > --- a/xen/include/xen/mm.h
> > +++ b/xen/include/xen/mm.h
> > @@ -56,7 +56,7 @@
> >  
> >  TYPE_SAFE(unsigned long, mfn);
> >  #define PRI_mfn          "05lx"
> > -#define INVALID_MFN      _mfn(~0UL)
> > +#define INVALID_MFN      (mfn_t){ ~0UL }
> 
> While I don't expect anyone to wish to use a suffix expression on
> this constant, for maximum compatibility this should still be fully
> parenthesized, I think. Of course this should be easy enough to
> do while committing.
> 
> Are you able to assure us that clang supports this gcc extension
> (compound literal for non-compound types)

AIUI this is a C99 feature, not a GCCism.  Clang supports it as far
back as 3.0: https://godbolt.org/g/YY97uj

Tim.


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