[NFC][libc++] Addresses LWG3905.

[Mordante]

Summary

Note libc++ implemented this in its initial version. It always used the type
from the C library and never validated whether it was an integer type.

Implements

• LWG3905 Type of std::fexcept_t

[philnik]

This looks more like a "Nothing to do" to me, since we don't actually have to change anything.

[ldionne]

libcxx/docs/Status/Cxx2cIssues.csv

1

libcxx/test/std/depr/depr.c.headers/fenv_h.compile.pass.cpp:60 has

fexcept_t fex = 0;

which is not conforming IIUC. We should change it.

[Mordante]

Addresses review comments.

[Mordante]

In D153285#4432970, @philnik wrote:

This looks more like a "Nothing to do" to me, since we don't actually have to change anything.

To me "Nothing to do" means no library implementation needs to make changes, not just us.
Otherwise when we don't implement a feature and it's removed from the Standard that would mean nothing to do too.

libcxx/docs/Status/Cxx2cIssues.csv

1

Nice catch!

[philnik]

In D153285#4435186, @Mordante wrote:

In D153285#4432970, @philnik wrote:

This looks more like a "Nothing to do" to me, since we don't actually have to change anything.

To me "Nothing to do" means no library implementation needs to make changes, not just us.
Otherwise when we don't implement a feature and it's removed from the Standard that would mean nothing to do too.

Well, no previously conforming implementation has to make changes. This LWG issue is specifically to make more implementations conforming.

[Mordante]

CI fixes.

[Mordante]

Retest CI seems to be a timing issue.

libcxx/docs/Status/Cxx2cIssues.csv

 "Issue #","Issue Name","Meeting","Status","First released version","Labels"
 "`2994 <https://wg21.link/LWG2994>`__","Needless UB for ``basic_string`` and ``basic_string_view``","Varna June 2023","","",""
 "`3884 <https://wg21.link/LWG3884>`__","``flat_foo`` is missing allocator-extended copy/move constructors","Varna June 2023","","","|flat_containers|"
 "`3885 <https://wg21.link/LWG3885>`__","``op`` should be in [zombie.names]","Varna June 2023","","",""
 "`3887 <https://wg21.link/LWG3887>`__","Version macro for ``allocate_at_least``","Varna June 2023","","",""
 "`3893 <https://wg21.link/LWG3893>`__","LWG 3661 broke ``atomic<shared_ptr<T>> a; a = nullptr;``","Varna June 2023","","",""
 "`3894 <https://wg21.link/LWG3894>`__","``generator::promise_type::yield_value(ranges::elements_of<Rng, Alloc>)`` should not be ``noexcept``","Varna June 2023","","",""
 "`3903 <https://wg21.link/LWG3903>`__","span destructor is redundantly noexcept","Varna June 2023","","",""
 "`3904 <https://wg21.link/LWG3904>`__","``lazy_split_view::outer-iterator``'s const-converting constructor isn't setting ``trailing_empty_``","Varna June 2023","","","|ranges|"
-"`3905 <https://wg21.link/LWG3905>`__","Type of ``std::fexcept_t``","Varna June 2023","","",""
+"`3905 <https://wg21.link/LWG3905>`__","Type of ``std::fexcept_t``","Varna June 2023","|Complete|","Clang 3.4",""
 "`3912 <https://wg21.link/LWG3912>`__","``enumerate_view::iterator::operator-`` should be ``noexcept``","Varna June 2023","","","|ranges|"
 "`3914 <https://wg21.link/LWG3914>`__","Inconsistent template-head of ``ranges::enumerate_view``","Varna June 2023","","","|ranges|"
 "`3915 <https://wg21.link/LWG3915>`__","Redundant paragraph about expression variations","Varna June 2023","","","|ranges|"
 "`3925 <https://wg21.link/LWG3925>`__","Concept ``formattable``'s definition is incorrect","Varna June 2023","|In Progress|","","|format|"
 "`3927 <https://wg21.link/LWG3927>`__","Unclear preconditions for ``operator[]`` for sequence containers","Varna June 2023","","",""
 "`3935 <https://wg21.link/LWG3935>`__","``template<class X> constexpr complex& operator=(const complex<X>&)`` has no specification","Varna June 2023","","",""
 "`3938 <https://wg21.link/LWG3938>`__","Cannot use ``std::expected`` monadic ops with move-only ``error_type``","Varna June 2023","","",""
 "`3940 <https://wg21.link/LWG3940>`__","``std::expected<void, E>::value()`` also needs ``E`` to be copy constructible","Varna June 2023","","",""
 "","","","","",""
 "`3343 <https://wg21.link/LWG3343>`__","Ordering of calls to ``unlock()`` and ``notify_all()`` in Effects element of ``notify_all_at_thread_exit()`` should be reversed","Not Yet Adopted","|Complete|","16.0",""
 "`3892 <https://wg21.link/LWG3892>`__","Incorrect formatting of nested ranges and tuples","Not Yet Adopted","|Complete|","17.0","|format|"
 "","","","","",""

libcxx/test/std/depr/depr.c.headers/fenv_h.compile.pass.cpp

 #error FE_UPWARD not defined
 #endif
 
 #ifndef FE_DFL_ENV
 #error FE_DFL_ENV not defined
 #endif
 
 fenv_t fenv = {};
-fexcept_t fex = 0;
+fexcept_t fex = fexcept_t();
 ASSERT_SAME_TYPE(int, decltype(::feclearexcept(0)));
 ASSERT_SAME_TYPE(int, decltype(::fegetexceptflag(&fex, 0)));
 ASSERT_SAME_TYPE(int, decltype(::feraiseexcept(0)));
 ASSERT_SAME_TYPE(int, decltype(::fesetexceptflag(&fex, 0)));
 ASSERT_SAME_TYPE(int, decltype(::fetestexcept(0)));
 ASSERT_SAME_TYPE(int, decltype(::fegetround()));
 ASSERT_SAME_TYPE(int, decltype(::fesetround(0)));
 ASSERT_SAME_TYPE(int, decltype(::fegetenv(&fenv)));
 ASSERT_SAME_TYPE(int, decltype(::feholdexcept(&fenv)));
 ASSERT_SAME_TYPE(int, decltype(::fesetenv(&fenv)));
 ASSERT_SAME_TYPE(int, decltype(::feupdateenv(&fenv)));