Previously, _Utf_view accepted any input_range, including reference-to-array types like char(&)[2], and stored it as the _M_base member. In such cases, _Utf_view was not assignable, failing the requirements of view concept.
This patch addresses the issue by adding the ranges::view constraint to the second template parameter of _Utf_view, and for clarity renaming it from _Range to _View. The constructor is also adjusted to accept its argument by value (views must be O(1) move-constructible). This prevents implicitly generated CTAD from deducing a reference type. This makes _Utf_view consistent with both other standard views and the wording from P2728R8: Unicode in the Library, Part 1: UTF Transcoding [1]. The explicit CTAD from viewable_range is not defined for _Utf_view because it depends on views::all_t, views::ref_view, and views::owning_view, which are declared in <ranges>. Consequently, users must explicitly cast the argument to a view or specify it as a template parameter. [1] https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2728r8.html libstdc++-v3/ChangeLog: * include/bits/unicode.h (_Utf_view): Rename the template parameter from _Range to _View and constrain it with ranges::view. (_Utf_view::_Utf_view): Accept by value instead of rvalue reference. * include/std/format (__format::__write_padded): Replace _Utf_view over const char32_t(&)[1] with span<const char32_t, 1>. * testsuite/ext/unicode/view.cc: Add checks if specialization of _Utf_view satisfy view. Wrap arrays into std::span before constructing _Utf_view. Reviewed-by: Jonathan Wakely <[email protected]> Signed-off-by: Tomasz Kamiński <[email protected]> --- v2 fixes typos in commit message. Tested on x86_64-linux. Pushed to trunk. libstdc++-v3/include/bits/unicode.h | 15 ++++++++------- libstdc++-v3/include/std/format | 2 +- libstdc++-v3/testsuite/ext/unicode/view.cc | 16 ++++++++++------ 3 files changed, 19 insertions(+), 14 deletions(-) diff --git a/libstdc++-v3/include/bits/unicode.h b/libstdc++-v3/include/bits/unicode.h index 44872db4ed6..09f7c2d7bfb 100644 --- a/libstdc++-v3/include/bits/unicode.h +++ b/libstdc++-v3/include/bits/unicode.h @@ -695,13 +695,14 @@ namespace __unicode friend class _Utf_iterator; }; - template<typename _ToFormat, ranges::input_range _Range> + template<typename _ToFormat, ranges::input_range _View> + requires ranges::view<_View> class _Utf_view - : public ranges::view_interface<_Utf_view<_ToFormat, _Range>> + : public ranges::view_interface<_Utf_view<_ToFormat, _View>> { - using _Iterator = _Utf_iterator<ranges::range_value_t<_Range>, - _ToFormat, ranges::iterator_t<_Range>, - ranges::sentinel_t<_Range>>; + using _Iterator = _Utf_iterator<ranges::range_value_t<_View>, + _ToFormat, ranges::iterator_t<_View>, + ranges::sentinel_t<_View>>; template<typename _Iter, typename _Sent> constexpr auto @@ -725,11 +726,11 @@ namespace __unicode return _Iterator(__last, __last); } - _Range _M_base; + _View _M_base; public: constexpr explicit - _Utf_view(_Range&& __r) : _M_base(std::forward<_Range>(__r)) { } + _Utf_view(_View __r) : _M_base(std::move(__r)) { } constexpr auto begin() { return _M_begin(ranges::begin(_M_base), ranges::end(_M_base)); } diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format index 1102ac8f6e8..f64f35a202e 100644 --- a/libstdc++-v3/include/std/format +++ b/libstdc++-v3/include/std/format @@ -845,7 +845,7 @@ namespace __format { // Encode fill char as multiple code units of type _CharT. const char32_t __arr[1]{ __fill_char }; - _Utf_view<_CharT, const char32_t(&)[1]> __v(__arr); + _Utf_view<_CharT, span<const char32_t, 1>> __v(__arr); basic_string<_CharT> __padstr(__v.begin(), __v.end()); __padding = __padstr; while (__l-- > 0) diff --git a/libstdc++-v3/testsuite/ext/unicode/view.cc b/libstdc++-v3/testsuite/ext/unicode/view.cc index 40c8fcf34fb..677a21d8c1f 100644 --- a/libstdc++-v3/testsuite/ext/unicode/view.cc +++ b/libstdc++-v3/testsuite/ext/unicode/view.cc @@ -7,6 +7,10 @@ namespace uc = std::__unicode; using namespace std::string_view_literals; +static_assert( std::ranges::view<uc::_Utf8_view<std::string_view>> ); +static_assert( std::ranges::view<uc::_Utf16_view<std::string_view>> ); +static_assert( std::ranges::view<uc::_Utf32_view<std::string_view>> ); + template<std::ranges::range View> constexpr void compare(View v, std::basic_string_view<std::ranges::range_value_t<View>> s) @@ -87,18 +91,18 @@ test_illformed_utf16() compare(uc::_Utf16_view(s.substr(0, 1)), r); compare(uc::_Utf16_view(s.substr(1, 1)), r); std::array s2{ s[0], s[0] }; - compare(uc::_Utf16_view(s2), u"\uFFFD\uFFFD"sv); + compare(uc::_Utf16_view(std::span(s2)), u"\uFFFD\uFFFD"sv); std::array s3{ s[0], s[0], s[1] }; - compare(uc::_Utf16_view(s3), u"\uFFFD\N{CLOWN FACE}"sv); + compare(uc::_Utf16_view(std::span(s3)), u"\uFFFD\N{CLOWN FACE}"sv); std::array s4{ s[1], s[0] }; - compare(uc::_Utf16_view(s4), u"\uFFFD\uFFFD"sv); + compare(uc::_Utf16_view(std::span(s4)), u"\uFFFD\uFFFD"sv); std::array s5{ s[1], s[0], s[1] }; - compare(uc::_Utf16_view(s5), u"\uFFFD\N{CLOWN FACE}"sv); + compare(uc::_Utf16_view(std::span(s5)), u"\uFFFD\N{CLOWN FACE}"sv); std::array<char16_t, 2> s6{ 0xDC00, 0xDC01 }; - compare(uc::_Utf16_view(s6), u"\uFFFD\uFFFD"sv); + compare(uc::_Utf16_view(std::span(s6)), u"\uFFFD\uFFFD"sv); std::array<char16_t, 2> s7{ 0xD7FF, 0xDC00 }; - compare(uc::_Utf16_view(s7), u"\uD7FF\uFFFD"sv); + compare(uc::_Utf16_view(std::span(s7)), u"\uD7FF\uFFFD"sv); } constexpr void -- 2.51.0
