Fznamznon added a comment.
> What do you mean with libstdc++ is fine?
What I mean is when I do (current patch is applied to clang):
source/llvm-project/build/bin/clang++ -std=c++20 t.cpp -c // compilation
succeeds
But when I do (libc++ is built together with clang)
source/llvm-project/build/bin/clang++ -std=c++20 t.cpp -stdlib=libc++ -c
t.cpp:4:15: error: static assertion failed due to requirement
'!std::is_invocable_v<const std::ranges::__crend::__fn, int (&)[]>'
4 | static_assert(!std::is_invocable_v<RangeCREndT, int (&)[]>);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
> Based on the bug and this patch I am correct that "transformation" of an
> array of unknown bounds to anarray of known bounds only happens with an
> explicit cast and not implicitly?
Yes, type is changed only for explicit casts.
> I have a strong suspicion that this patch changes the test to
Well technically it only changes explicit casts, so no. With this patch this
static assertion still fails
static_assert(std::is_same<int (&)[1], int(&)[]>::value);
What I'm seeing is that in libc++ there is a bunch of explicit static casts in
`ranges::__crend::__fn` that endup transformed:
namespace ranges {
namespace __crend {
struct __fn {
template <class _Tp>
requires is_lvalue_reference_v<_Tp&&>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
constexpr auto operator()(_Tp&& __t) const
noexcept(noexcept(ranges::rend(static_cast<const
remove_reference_t<_Tp>&>(__t))))
-> decltype( ranges::rend(static_cast<const
remove_reference_t<_Tp>&>(__t)))
{ return ranges::rend(static_cast<const
remove_reference_t<_Tp>&>(__t)); }
template <class _Tp>
requires is_rvalue_reference_v<_Tp&&>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
constexpr auto operator()(_Tp&& __t) const
noexcept(noexcept(ranges::rend(static_cast<const _Tp&&>(__t))))
-> decltype( ranges::rend(static_cast<const _Tp&&>(__t)))
{ return ranges::rend(static_cast<const _Tp&&>(__t)); }
};
} // namespace __crend
Is that expected?
Please note that other implementations would do the same transformation and
that is the point of this bugfix:
https://godbolt.org/z/ff8f3YEbz
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D152003/new/
https://reviews.llvm.org/D152003
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