Re: [PATCH] handle expressions in __builtin_has_attribute (PR 88383)

[Jakub Jelinek <jakub at redhat dot com>]

On Thu, Dec 13, 2018 at 12:48:18PM -0700, Martin Sebor wrote:
> > The support is necessary in order to determine the attributes
> > in expressions such as:
> > 
> >    struct S { __attribute__ ((packed)) int a[32]; };
> > 
> >    extern struct S s;
> > 
> >    _Static_assert (__builtin_has_attribute (s.a, packed));
> 
> An example involving types might be a better one:
> 
>   typedef __attribute__ ((may_alias)) int* BadInt;
> 
>   void f (BadInt *p)
>   {
>     _Static_assert (__builtin_has_attribute (*p, may_alias));
>   }

So how is the builtin defined then?  Is the argument always an expression
and you only return whether its type has the attribute, or do something
different if the expression is of certain kind?
Perhaps it would be better have two builtins, one would always take
type from the expression, the other would only accept decls (or perhaps
some syntax for the FIELD_DECLs).

	Jakub