Hi Jens,

On Mar. 6 May 2025 at 02:42, Jens Maurer <jens.maurer_at_[hidden]> wrote:
> On 05/05/2025 18.24, Jₑₙₛ Gustedt via Liaison wrote:

(...)

> Indeed, but
>
> ( (void)1, 1 )
>
> does not cause problems with the syntax for conditional-expression.
>
> But there is an extra rule in C23 6.6 paragraph 3:
>
> "Constant expressions shall not contain assignment, increment, decrement, function-call, or comma
> operators, except when they are contained within a subexpression that is not evaluated."
>
> > What the historical reason
> > for this would be, I don't know, and if would be easy to change I
> > don't know either.
>
> Having static_assert(x) be an expression of void type and then just writing
>
> ( static_assert(whatever), x )
>
> seems like the most user-friendly syntax.
> (If you're in a macro, you likely want some outer parentheses anyway.)

I do not think that this works in C23. As far as I can see, when writing:

  ((void)1, 1);

the expression is not an integer constant expression, even with the
extra parentheses. At least, both GCC and clang complain about it.
Here are a few extra examples:

  https://godbolt.org/z/YqM45MjPz

But at the end, my point it that if static_assert() yields an integer,
it can be used with both the comma operator and with other operator
(such as the +, c.f. prior works). So, yielding an integer does not
close any doors.


Yours sincerely,
Vincent Mailhol