Deprecating arithmetic on std::atomic<void*>

[Florian Weimer]

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); }

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

Florian