On Wed, 2023-01-18 at 17:10 +0100, Alexander Lobakin wrote:
>
> Have you tried combining it with FIELD_PREP() using
> __builtin_choose_expr() + __builtin_is_constexpr() (or
> __builtin_constant_p() depending on which will satisfy the compiler)?
> I'm not saying it's 100% possible, but worth trying.
>
I haven't tried it that way, but I tried rewriting FIELD_PREP() itself
to be constant-compatible, and as soon as the compiler saw
__builtin_constant_p() in the initializer it already complained that it
was non-constant...
I didn't think of __builtin_choose_expr, but it doesn't work either
because it only promises that the unused expression is not *evaluated*,
not that it's not "looked at", so it still complains both ways (in the
constant case that you can't have ({ }) braced groups, and in the non-
constant case that the _CONST version is bad...
johannes
