Re: C++ PATCH to abate shift warnings (PR c++/68979)

[Jason Merrill <jason@redhat.com>]

On 01/12/2016 09:05 AM, Marek Polacek wrote:
> On Tue, Jan 12, 2016 at 08:27:47AM -0500, Jason Merrill wrote:
>> Changing the diagnostic is OK, but cxx_eval_check_shift_p should return true
>> regardless of flag_permissive, so that SFINAE results follow the standard.
>
> There's a complication, because if I keep returning true, we'll give a
> compile-time error like this:
>
> permissive-1.C:5:18: warning: left operand of shift expression ‘(-1 << 4)’ is
> negative [-fpermissive]
>   enum A { AA = -1 << 4 }; // { dg-warning "operand of shift expression" "" {
> target c++11 } }
>
> permissive-1.C:5:21: error: enumerator value for ‘AA’ is not an integer
> constant
>   enum A { AA = -1 << 4 }; // { dg-warning "operand of shift expression" "" {
> target c++11 } }
>
> So I suppose that wouldn't really help.  :(

In that case, we need to return (!flag_permissive || ctx->quiet).

Jason