[gcc r13-8302] libstdc++: Allow explicit conversion of string views with different traits
Jonathan Wakely
redi@gcc.gnu.org
Thu Feb 8 15:50:43 GMT 2024
https://gcc.gnu.org/g:d49262a7126719e861479385eb7775517bfa8a19
commit r13-8302-gd49262a7126719e861479385eb7775517bfa8a19
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.
(cherry picked from commit f60d7e1c64518936797ec1009cb49f72f8fe45b9)
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 4cf5bc30fec5..0f4b22435335 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 0d0fd0f3775a..6d253c835311 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
@@ -116,23 +116,10 @@ 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 de2244467242..2096de76badd 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
@@ -116,23 +116,10 @@ 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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