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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-1228] libstdc++: Implement LWG 3403 for std::ranges::ssize Date: Fri, 4 Jun 2021 20:43:02 +0000 (GMT) [thread overview] Message-ID: <20210604204302.C309839A0456@sourceware.org> (raw) https://gcc.gnu.org/g:621ea10ca060ba19ec693aa73b5e29d553cca849 commit r12-1228-g621ea10ca060ba19ec693aa73b5e29d553cca849 Author: Jonathan Wakely <jwakely@redhat.com> Date: Fri Jun 4 20:28:04 2021 +0100 libstdc++: Implement LWG 3403 for std::ranges::ssize I already changed the constraints for ranges::ssize to use ranges::size, this implements the rest of LWG 3403, so that the returned type is the signed type corresponding to the result of ranges::size. Signed-off-by: Jonathan Wakely <jwakely@redhat.com> libstdc++-v3/ChangeLog: * include/bits/ranges_base.h (_SSize): Return the result of ranges::size converted to the wider of make-signed-like-t<S> and ptrdiff_t, rather than the ranges different type. * testsuite/std/ranges/access/ssize.cc: Adjust expected result for an iota_view that uses an integer class type for its difference_type. Diff: --- libstdc++-v3/include/bits/ranges_base.h | 22 ++++++++++++++++------ libstdc++-v3/testsuite/std/ranges/access/ssize.cc | 9 ++++++--- 2 files changed, 22 insertions(+), 9 deletions(-) diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h index 61d91eb8389..e3c3962bcd9 100644 --- a/libstdc++-v3/include/bits/ranges_base.h +++ b/libstdc++-v3/include/bits/ranges_base.h @@ -425,22 +425,32 @@ namespace ranges struct _SSize { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3403. Domain of ranges::ssize(E) doesn't match ranges::size(E) template<typename _Tp> requires requires (_Tp& __t) { _Size{}(__t); } constexpr auto operator()(_Tp&& __t) const noexcept(noexcept(_Size{}(__t))) { - using __iter_type = decltype(_Begin{}(__t)); - using __diff_type = iter_difference_t<__iter_type>; - using __gnu_cxx::__int_traits; auto __size = _Size{}(__t); - if constexpr (integral<__diff_type>) + using __size_type = decltype(__size); + // Return the wider of ptrdiff_t and make-signed-like-t<__size_type>. + if constexpr (integral<__size_type>) { - if constexpr (__int_traits<__diff_type>::__digits + using __gnu_cxx::__int_traits; + if constexpr (__int_traits<__size_type>::__digits < __int_traits<ptrdiff_t>::__digits) return static_cast<ptrdiff_t>(__size); + else + return static_cast<make_signed_t<__size_type>>(__size); } - return static_cast<__diff_type>(__size); +#if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__ + // For strict-ansi modes integral<__int128> is false + else if constexpr (__detail::__is_int128<__size_type>) + return static_cast<unsigned __int128>(__size); +#endif + else // Must be one of __max_diff_type or __max_size_type. + return __detail::__max_diff_type(__size); } }; diff --git a/libstdc++-v3/testsuite/std/ranges/access/ssize.cc b/libstdc++-v3/testsuite/std/ranges/access/ssize.cc index b00ec5db1f8..f53f462580c 100644 --- a/libstdc++-v3/testsuite/std/ranges/access/ssize.cc +++ b/libstdc++-v3/testsuite/std/ranges/access/ssize.cc @@ -76,9 +76,12 @@ void test06() { auto i = std::views::iota(1ull, 5u); - auto s = std::ranges::ssize(i); - using R = std::ranges::range_difference_t<decltype(i)>; - static_assert( std::same_as<decltype(s), R> ); + auto s = std::ranges::size(i); + auto ss = std::ranges::ssize(i); + // std::ranges::range_difference_t<decltype(i)> is larger than long long, + // but LWG 3403 says ranges::ssize(i) returns the signed version of the + // type that ranges::size(i) returns, not the range's difference_type. + static_assert( std::same_as<decltype(ss), std::make_signed_t<decltype(s)>> ); VERIFY( s == 4 ); }
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