Re: Deprecating arithmetic on std::atomic<void*>

[Jonathan Wakely <jwakely at redhat dot com>]

On 20/04/17 11:43 +0200, Florian Weimer wrote:
> On 04/20/2017 11:25 AM, Jonathan Wakely wrote:
>
> > > I mean, with -pedantic-errors we already error on void * arighmetics
> > > or function pointer arithmetics.  If std::atomic<void*> would use
> > > the void * arithmetics, it would also reject it.  Or does it use integer
> > > arithmetics instead?
> >
> > No, it does it on void*, but the __atomic built-ins still perform that
> > arithmetic even with -pedantic-errors.
>
> sizeof is not defined for the relevant types, either, and already 
> triggers a warning by default:
>
> t.cc:25:58: warning: invalid application of ‘sizeof’ to a void type 
> [-Wpointer-arith]
>   _M_type_size(ptrdiff_t __d) const { return __d * sizeof(_PTp); }

That could be easily avoided if we care about supporting arithmetic on
std::atomic<void*>.

> I think the actual problem here is the suppression of warnings from 
> system headers.

The atomic built-ins still don't warn even with -Wsystem-headers