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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r14-8740] libstdc++: Allow explicit conversion of string views with different traits Date: Fri, 2 Feb 2024 10:24:23 +0000 (GMT) [thread overview] Message-ID: <20240202102423.A80063857C51@sourceware.org> (raw) https://gcc.gnu.org/g:f60d7e1c64518936797ec1009cb49f72f8fe45b9 commit r14-8740-gf60d7e1c64518936797ec1009cb49f72f8fe45b9 Author: Jonathan Wakely <jwakely@redhat.com> Date: Thu Feb 1 21:40:33 2024 +0000 libstdc++: Allow explicit conversion of string views with different traits This was changed by LWG 3857. libstdc++-v3/ChangeLog: * include/std/string_view (basic_string_view(R&&)): Remove constraint that traits_type must be the same, as per LWG 3857. * testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc: Explicit conversion between different specializations should be allowed. * testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc: Likewise. Diff: --- libstdc++-v3/include/std/string_view | 2 -- .../basic_string_view/cons/char/range_c++20.cc | 21 ++++----------------- .../basic_string_view/cons/wchar_t/range_c++20.cc | 21 ++++----------------- 3 files changed, 8 insertions(+), 36 deletions(-) diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view index b444b5b9a39b..e30a9c1768e0 100644 --- a/libstdc++-v3/include/std/string_view +++ b/libstdc++-v3/include/std/string_view @@ -167,8 +167,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION && (!requires (_DRange& __d) { __d.operator ::std::basic_string_view<_CharT, _Traits>(); }) - && (!requires { typename _DRange::traits_type; } - || is_same_v<typename _DRange::traits_type, _Traits>) constexpr explicit basic_string_view(_Range&& __r) noexcept(noexcept(ranges::size(__r)) && noexcept(ranges::data(__r))) diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc index 5d0396563fd8..bae8da1d2645 100644 --- a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc +++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc @@ -115,23 +115,10 @@ test02() static_assert( ! std::is_constructible_v<std::string_view, V1> ); using V2 = std::basic_string_view<char, __gnu_cxx::char_traits<char>>; - // V2::traits_type is not the right type - static_assert( ! std::is_constructible_v<std::string_view, V2> ); - - struct V3 : V2 - { - private: - using V2::traits_type; - }; - // V3::traits_type is not a valid (accessible) type - static_assert( std::is_constructible_v<std::string_view, V3> ); - - struct V4 : V2 - { - using traits_type = std::string_view::traits_type; - }; - // V4::traits_type is the right type - static_assert( std::is_constructible_v<std::string_view, V4> ); + // LWG 3857 + // basic_string_view should allow explicit conversion when only traits vary + static_assert( std::is_constructible_v<std::string_view, V2> ); + static_assert( ! std::is_convertible_v<V2, std::string_view> ); } void diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc index d6996a1dd6f0..3cf154d8602d 100644 --- a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc +++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc @@ -115,23 +115,10 @@ test02() static_assert( ! std::is_constructible_v<std::wstring_view, V1> ); using V2 = std::basic_string_view<wchar_t, __gnu_cxx::char_traits<wchar_t>>; - // V2::traits_type is not the right type - static_assert( ! std::is_constructible_v<std::wstring_view, V2> ); - - struct V3 : V2 - { - private: - using V2::traits_type; - }; - // V3::traits_type is not a valid (accessible) type - static_assert( std::is_constructible_v<std::wstring_view, V3> ); - - struct V4 : V2 - { - using traits_type = std::wstring_view::traits_type; - }; - // V4::traits_type is the right type - static_assert( std::is_constructible_v<std::wstring_view, V4> ); + // LWG 3857 + // basic_string_view should allow explicit conversion when only traits vary + static_assert( std::is_constructible_v<std::wstring_view, V2> ); + static_assert( ! std::is_convertible_v<V2, std::wstring_view> ); } void
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