On Thu, 15 May 2025 at 11:14, Jonathan Wakely <jwak...@redhat.com> wrote:
>
> On Wed, 14 May 2025 at 20:18, Luc Grosheintz <luc.groshei...@gmail.com> wrote:
> >
> > The standard states that the IndexType must be a signed or unsigned
> > integer. This mandate was implemented using `std::is_integral_v`. Which
> > also includes (among others) char and bool, which neither signed nor
> > unsigned integers.
> >
> > libstdc++-v3/ChangeLog:
> >
> > * include/std/mdspan: Implement the mandate for extents as
> > signed or unsigned integer and not any interal type.
> > * testsuite/23_containers/mdspan/extents/class_mandates_neg.cc:
> > Check
> > that extents<char,...> and extents<bool,...> are invalid.
> > * testsuite/23_containers/mdspan/extents/misc.cc: Update
> > tests to avoid `char` and `bool` as IndexType.
> > ---
> > libstdc++-v3/include/std/mdspan | 3 ++-
> > .../23_containers/mdspan/extents/class_mandates_neg.cc | 10 +++++++---
> > .../testsuite/23_containers/mdspan/extents/misc.cc | 8 ++++----
> > 3 files changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/libstdc++-v3/include/std/mdspan
> > b/libstdc++-v3/include/std/mdspan
> > index aee96dda7cd..22509d9c8f4 100644
> > --- a/libstdc++-v3/include/std/mdspan
> > +++ b/libstdc++-v3/include/std/mdspan
> > @@ -163,7 +163,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > template<typename _IndexType, size_t... _Extents>
> > class extents
> > {
> > - static_assert(is_integral_v<_IndexType>, "_IndexType must be
> > integral.");
> > + static_assert(__is_standard_integer<_IndexType>::value,
> > + "_IndexType must be a signed or unsigned integer.");
>
> GCC's diagnostics never end with a full stop (aka period), and we
> follow that convention for our static assertions.
>
> So I'll remove the '.' at the end of the string literal, and then push
> this to trunk.
>
>
> > static_assert(
> > (__mdspan::__valid_static_extent<_Extents, _IndexType> && ...),
> > "Extents must either be dynamic or representable as _IndexType");
I've just noticed that this static_assert refers to "Extents" without
the leading underscore, but "_IndexType" with a leading underscore.
I think it's OK to omit the leading underscore, it might be a bit more
user-friendly and I don't think anybody will be confused by the fact
it's not identical to the real template parameter. But we should
either do it consistently for _Extents and _IndexType or for neither
of them.
Anybody want to argue for or against underscores?
