Re: [PATCH 1/2] asm qualifiers (PR55681)

[Segher Boessenkool <segher@kernel.crashing.org>]

On Thu, Nov 29, 2018 at 11:14:45PM +0000, Joseph Myers wrote:
> On Thu, 29 Nov 2018, Segher Boessenkool wrote:
> 
> > > What's the basis for allowing duplicates for C but not for C++?
> > 
> > It is the status quo.  It would make sense to allow duplicates for C++ as
> > well, sure.  If that is preferred I can make a patch for it?
> 
> Duplicate qualifiers are allowed *in declarations* for C (as per C99).  

And I used type-qualifier-list[opt] there, to start with.

> They aren't allowed in asm.  I'd think the most obvious thing would be not 
> to allow duplicate qualifiers in asm at all (but still allow any ordering 
> of volatile, goto and inline).  Essentially, the use in asm is just 
> reusing a keyword in a different context, so I don't think duplicates 
> being allowed in declarations is relevant to allowing them in asm (any 
> more than it indicates that __attribute__ ((const const const)) should be 
> allowed just because const is a valid attribute).

So "asm const restrict" is allowed, but "asm const const restrict" isn't.
Hrm.  That means we'll have to keep track of the ignored qualifiers.
(There aren't any ignored asm qualifiers in C++ so no such issue there).

What do you want done with const and restrict (and _Atomic, which is
allowed by the current grammar)?


Segher