Dear Tom and other Unicoders,

I would like to bring your attention to a paper that seems to have slipped
through the cracks and has not been reviewed by SG16 despite having a
critical text/encoding aspect to it. This paper is P3068
<https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3068r2.html>
"Allowing
exception throwing in constant-evaluation".

It looks like a mainly language feature so it's not very surprising that we
missed it. However, enabling exceptions at compile time opens an important
question about compile-time exception message encoding (and indeed it
touches exception::what) which was previously moot. It is closely related
to LWG4087 <https://cplusplus.github.io/LWG/issue4087> which we discussed
recently and I think we are in a unique position to not repeat mistakes
from decades ago. Instead we can make exception messages usable portably at
compile time and compatible with other compile-time facilities. And even if
we don't want to do that, at the very least we need to revise the part of
the wording that indirectly talks about the C locale since it is obviously
incorrect at compile time.

I brought up this issue during the review of this paper by LEWG and, if I
am not mistaken, Eddie voiced his support but unfortunately LEWG completely
ignored it for some reason. So I suggest that SG16 should take initiative
and review this before it is too late and the feature ships leaving
exceptions in an underspecified and not very usable state, incompatible
with formatting facilities. This issue is so severe in my opinion that I
voted against forwarding this paper even though I am otherwise in favor of
the language facility itself.

Cheers,
Victor