Hi Martin,
On Mon, 27 Feb 2017, Martin Sebor wrote:
> Sorry to be jumping in so late. I only noticed this bit now.
>
> I would suggest to say that these new built-ins evaluate to integer
> constant expressions when their arguments do. Not all C programmers
> are familiar with C++ constexpr so they may not understand the use
> use case. The request for these built-ins also came from a C user
> and was specifically motivated by avoiding -Woverflow warnings so
> adding an example demonstrating that might be helpful as well.
> Something like this:
>
> ... Calls to these built-ins with integer constant arguments
> evaluate to integer constants expressions.</p>
> <p>For example, in the following, <code>c</code> is assigned
> the result of <code>a * b</code> only if the multiplication
> does not overflow, otherwise it is assigned the value zero.
> The multiplication is performed at compile-time and without
> triggering a <code>-Woverflow</code> warning.
</p>
> <blockquote>
> <pre>enum {
> a = 12345678,
> b = 87654321,
> c = __builtin_mul_overflow_p (a, b, a) ? 0 : a * b
> };</pre>
> </blockquote></li>
this works for me, modulo the closing </p> which I believe will be
necessary. Were you seeing approval for this from someone? (If so,
that may not have been me. ;-)
Gerald
