Re: PING [PATCH] fix ICE in __builtin_has_attribute (PR 88383 and 89288)

[Jakub Jelinek <jakub at redhat dot com>]

On Thu, Mar 21, 2019 at 04:19:37PM -0600, Martin Sebor wrote:
> > Say that the argument is either a type or an expression that is
> > either an identifier (for C++ id-expression) to cover 1) and
> > a postfix expression with . or -> operator (to cover COMPONENT_REF)?
> 
> That doesn't look easy to understand.

Why?  Those users that don't read corresponding language standards
will just see the compiler diagnosing any uses but those 3 kinds
and can then just read the documentation which will show in examples what is
accepted and what it will do.

> > We do not want to allow INDIRECT_REF, ARRAY_REF, etc.
> 
> Why not?  What exactly is the concern?

Because only the . and -> operators are needed to get at the non-static
member declaration.  INDIRECT_REF or ARRAY_REF aren't useful for that,
and then it raises the question what exactly is supposed to be the behavior
when you use *expr or expr[0] or expr->field[0].  Those expression don't
have any decl, so we'd be back at your suggestion to pretty randomly
sometimes return DECL_ATTRIBUTES, sometimes TYPE_ATTRIBUTES, sometimes both.
That is just a bad design.  If people want type attributes, they should use
__typeof or decltype or just type itself in the argument.

	Jakub