On Fri, Nov 14, 2025 at 6:55 PM Hewill Kang <[email protected]> wrote:
> LGTM. > > I know that CTAD wasn't provided due to heavy header considerations. But > wouldn't providing CTAD be an enhancement? > At least in terms of user convenience. > I care much more about the use of libstdc++ compile time performance, that convenience of the libstdc++ authors (only people that should use it). If we get official Utf_view, it should have the deduction guide in place. > > Tomasz Kamiński <[email protected]> 於 2025年11月15日 週六 上午1:06寫道： > >> 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 requirement to be a 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 >> cosntructing _Utf_view. >> --- >> 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 >> >>
