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author | Jonathan Wakely <jwakely@redhat.com> | 2019-09-09 12:12:38 +0100 |
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committer | Jonathan Wakely <redi@gcc.gnu.org> | 2019-09-09 12:12:38 +0100 |
commit | 27dada7d06926cc7ef6293fbbf0629f523b49e48 (patch) | |
tree | e3d6a047ad28871046ab9b7279b472cfedd58a7a | |
parent | ca47c3987c09df50cd9504652e4a8f6f8656bf94 (diff) | |
download | gcc-27dada7d06926cc7ef6293fbbf0629f523b49e48.zip gcc-27dada7d06926cc7ef6293fbbf0629f523b49e48.tar.gz gcc-27dada7d06926cc7ef6293fbbf0629f523b49e48.tar.bz2 |
Improve constraints for std::span constructors
This patch simplifies the constraints on the constructors from arrays by
removing the redundant checks that element_type and value_type are
convertible to element_type. The incorrect uses of __adl_data in those
constructors are removed as well (they should use std::data not
std::ranges::data, and the former doesn't use ADL).
The range/container constructors are now constrained to exclude all
specializations of std::span, not just the current instantiation. The
range constructor now also checks s subset of the contiguous_range
requirements.
All relevant constructor constraints now use the _Require helper in
order to short circuit and avoid unnecessary instantiations after the
first failed constraint.
A new constructor supports initialization from different specializations
of std::span<OtherType, OtherExtent>, as specified in the C++20 draft.
* include/bits/range_access.h (__adl_to_address): Remove.
* include/std/span (__is_base_derived_safe_convertible_v): Replace
with span::__is_compatible.
(__is_std_array_v): Replace with __is_std_array class template and
partial specializations.
(__is_std_array, __is_std_span): New class templates and partial
specializations.
(span::__is_compatible): New alias template for SFINAE constraints.
(span::span(element_type (&)[N])): Remove redundant constraints. Do
not use __adl_data to obtain a pointer.
(span::span(array<value_type, N>&)): Likewise.
(span::span(const array<value_type, N>&)): Likewise.
[_GLIBCXX_P1394] (span::iter_reference_t, span::iterator_t)
(span::iter_value_t, span::derived_from): New alias templates for
SFINAE constraints, until the equivalents are supported in <concepts>
and <iterator>.
[_GLIBCXX_P1394] (span::__is_compatible_iterator): New alias template
for SFINAE constraints.
[_GLIBCXX_P1394] (span::is_compatible_range): New class template for
SFINAE constraints.
[_GLIBCXX_P1394] (span::span(Range&&)): Improve constraints.
[_GLIBCXX_P1394] (span::span(ContiguousIterator, Sentinel)): Likewise.
Use std::to_address instead of __adl_to_address.
[_GLIBCXX_P1394] (span::span(ContiguousIterator, size_type)): Likewise.
[!_GLIBCXX_P1394] (span::__is_compatible_container): New alias
template for SFINAE constraints.
[!_GLIBCXX_P1394] (span::span(Container&))
(span::span(const Container&)): Improve constraints.
[!_GLIBCXX_P1394] (span::span(pointer, size_type))
(span::span(pointer, pointer)): Remove redundant cast of pointer.
(span(const span<OType, OExtent>&)): New constructor.
From-SVN: r275513
-rw-r--r-- | libstdc++-v3/ChangeLog | 34 | ||||
-rw-r--r-- | libstdc++-v3/include/bits/range_access.h | 7 | ||||
-rw-r--r-- | libstdc++-v3/include/std/span | 214 |
3 files changed, 155 insertions, 100 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index e135e85..0aff148 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,37 @@ +2019-09-09 Jonathan Wakely <jwakely@redhat.com> + + * include/bits/range_access.h (__adl_to_address): Remove. + * include/std/span (__is_base_derived_safe_convertible_v): Replace + with span::__is_compatible. + (__is_std_array_v): Replace with __is_std_array class template and + partial specializations. + (__is_std_array, __is_std_span): New class templates and partial + specializations. + (span::__is_compatible): New alias template for SFINAE constraints. + (span::span(element_type (&)[N])): Remove redundant constraints. Do + not use __adl_data to obtain a pointer. + (span::span(array<value_type, N>&)): Likewise. + (span::span(const array<value_type, N>&)): Likewise. + [_GLIBCXX_P1394] (span::iter_reference_t, span::iterator_t) + (span::iter_value_t, span::derived_from): New alias templates for + SFINAE constraints, until the equivalents are supported in <concepts> + and <iterator>. + [_GLIBCXX_P1394] (span::__is_compatible_iterator): New alias template + for SFINAE constraints. + [_GLIBCXX_P1394] (span::is_compatible_range): New class template for + SFINAE constraints. + [_GLIBCXX_P1394] (span::span(Range&&)): Improve constraints. + [_GLIBCXX_P1394] (span::span(ContiguousIterator, Sentinel)): Likewise. + Use std::to_address instead of __adl_to_address. + [_GLIBCXX_P1394] (span::span(ContiguousIterator, size_type)): Likewise. + [!_GLIBCXX_P1394] (span::__is_compatible_container): New alias + template for SFINAE constraints. + [!_GLIBCXX_P1394] (span::span(Container&)) + (span::span(const Container&)): Improve constraints. + [!_GLIBCXX_P1394] (span::span(pointer, size_type)) + (span::span(pointer, pointer)): Remove redundant cast of pointer. + (span(const span<OType, OExtent>&)): New constructor. + 2019-09-06 Jonathan Wakely <jwakely@redhat.com> * include/bits/range_access.h (ssize): Define for C++20. diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h index c574414..bc137d7 100644 --- a/libstdc++-v3/include/bits/range_access.h +++ b/libstdc++-v3/include/bits/range_access.h @@ -396,13 +396,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION constexpr auto __adl_empty(_Container& __cont) noexcept(noexcept(empty(__cont))) { return empty(__cont); } - -#if defined(_GLIBCXX_P1394) && _GLIBCXX_P1394 - template <typename _Container> - constexpr auto - __adl_to_address(_Container& __cont) noexcept(noexcept(to_address(__cont))) - { return to_address(__cont); } -#endif // P1394 and new contiguous_iterator requirements [iterator.concept.contiguous] #endif // C++20 _GLIBCXX_END_NAMESPACE_VERSION diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span index 95d778b..1a0d61c 100644 --- a/libstdc++-v3/include/std/span +++ b/libstdc++-v3/include/std/span @@ -53,24 +53,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION inline constexpr size_t dynamic_extent = static_cast<size_t>(-1); + template<typename _Type, size_t _Extent> + class span; + namespace __detail { - template<typename _Element, typename _ToElement> - static constexpr inline bool __is_base_derived_safe_convertible_v - = is_convertible_v<_Element (*)[], _ToElement (*)[]>; + template<typename _Tp> + struct __is_std_span : false_type { }; + + template<typename _Tp, size_t _Num> + struct __is_std_span<span<_Tp, _Num>> : true_type { }; template<typename _Tp> - inline constexpr bool __is_std_array_v = false; + struct __is_std_array : false_type { }; template<typename _Tp, size_t _Num> - inline constexpr bool - __is_std_array_v<_GLIBCXX_STD_C::array<_Tp, _Num>> = true; + struct __is_std_array<_GLIBCXX_STD_C::array<_Tp, _Num>> : true_type { }; #ifdef _GLIBCXX_DEBUG template<typename _Tp, size_t _Num> - inline constexpr bool - __is_std_array_v<std::__debug::array<_Tp, _Num>> = true; -#endif // debug/array + struct __is_std_array<__debug::array<_Tp, _Num>> : true_type { }; +#endif template<size_t _Extent> class __extent_storage @@ -119,6 +122,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION return dynamic_extent; } + template<typename _Tp> + using __is_compatible = is_convertible<_Tp(*)[], _Type(*)[]>; + public: // member types using value_type = remove_cv_t<_Type>; @@ -154,41 +160,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION span(const span&) noexcept = default; template<size_t _ArrayExtent, - enable_if_t< - (_Extent == dynamic_extent || _ArrayExtent == _Extent) - && __detail::__is_base_derived_safe_convertible_v< - remove_pointer_t<decltype(::std::__adl_data( - ::std::declval<element_type (&)[_ArrayExtent]>()))>, - element_type>>* = nullptr> - constexpr span(element_type (&__arr)[_ArrayExtent]) - noexcept(noexcept(::std::__adl_data(__arr))) - : span(::std::__adl_data(__arr), _ArrayExtent) + enable_if_t<_Extent == dynamic_extent || _ArrayExtent == _Extent>* + = nullptr> + constexpr + span(element_type (&__arr)[_ArrayExtent]) noexcept + : span(static_cast<pointer>(__arr), _ArrayExtent) { } template<size_t _ArrayExtent, - enable_if_t< - (_Extent == dynamic_extent || _ArrayExtent == _Extent) - && __detail::__is_base_derived_safe_convertible_v< - remove_pointer_t<decltype(::std::__adl_data( - ::std::declval<const array<value_type, _ArrayExtent>&>()))>, - element_type>>* = nullptr> + enable_if_t<_Extent == dynamic_extent || _ArrayExtent == _Extent>* + = nullptr> constexpr - span(array<value_type, _ArrayExtent>& __arr) - noexcept(noexcept(::std::__adl_data(__arr))) - : span(::std::__adl_data(__arr), _ArrayExtent) + span(array<value_type, _ArrayExtent>& __arr) noexcept + : span(__arr.data(), _ArrayExtent) { } template<size_t _ArrayExtent, - enable_if_t< - (_Extent == dynamic_extent || _ArrayExtent == _Extent) - && __detail::__is_base_derived_safe_convertible_v< - remove_pointer_t<decltype(::std::__adl_data( - ::std::declval<const array<value_type, _ArrayExtent>&>()))>, - element_type>>* = nullptr> + enable_if_t<_Extent == dynamic_extent || _ArrayExtent == _Extent>* + = nullptr> constexpr - span(const array<value_type, _ArrayExtent>& __arr) - noexcept(noexcept(::std::__adl_data(__arr))) - : span(::std::__adl_data(__arr), _ArrayExtent) + span(const array<value_type, _ArrayExtent>& __arr) noexcept + : span(__arr.data(), _ArrayExtent) { } // NOTE: when the time comes, and P1394 - @@ -199,18 +191,49 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // and keep the crappy #else block // and then cry that NB comments failed C++20... // but maybe for C++23? -#if defined(_GLIBCXX_P1394) && _GLIBCXX_P1394 - template<typename _Range, - enable_if_t< - (_Extent == dynamic_extent) - && !is_same_v<remove_cvref_t<_Range>, span> - && !__detail::__is_std_array_v<remove_cvref_t<_Range>> - && !is_array_v<remove_cvref_t<_Range>> - && __detail::__is_base_derived_safe_convertible_v< - remove_pointer_t<decltype( - ::std::__adl_data(::std::declval<_Range&>()) - + ::std::__adl_size(::std::declval<_Range&>()))>, - element_type>>* = nullptr> +#ifdef _GLIBCXX_P1394 + private: + // FIXME: use std::iter_reference_t + template<typename _Iterator> + using iter_reference_t = decltype(*std::declval<_Iterator&>()); + // FIXME: use std::ranges::iterator_t + // N.B. constraint is needed to prevent a cycle when __adl_begin finds + // begin(span) which does overload resolution on span(Range&&). + template<typename _Rng, + typename _Rng2 = remove_cvref_t<_Rng>, + typename = enable_if_t<!__detail::__is_std_span<_Rng2>::value>> + using iterator_t = decltype(std::__adl_begin(std::declval<_Rng&>())); + // FIXME: use std::iter_value_t + template<typename _Iter> + using iter_value_t = typename iterator_traits<_Iter>::value_type; + // FIXME: use std::derived_from concept + template<typename _Derived, typename _Base> + using derived_from + = __and_<is_base_of<_Base, _Derived>, + is_convertible<const volatile _Derived*, const volatile _Base*>>; + // FIXME: require contiguous_iterator<_Iterator> + template<typename _Iter, + typename _Ref = iter_reference_t<_Iter>, + typename _Traits = iterator_traits<_Iter>, + typename _Tag = typename _Traits::iterator_category> + using __is_compatible_iterator + = __and_<derived_from<_Tag, random_access_iterator_tag>, + is_lvalue_reference<_Ref>, + is_same<iter_value_t<_Iter>, remove_cvref_t<_Ref>>, + __is_compatible<remove_reference_t<_Ref>>>; + + template<typename _Range> + using __is_compatible_range + = __is_compatible_iterator<iterator_t<_Range>>; + + public: + template<typename _Range, typename = _Require< + bool_constant<_Extent == dynamic_extent>, + __not_<__detail::__is_std_span<remove_cvref_t<_Range>>>, + __not_<__detail::__is_std_array<remove_cvref_t<_Range>>>, + __not_<is_array<remove_reference_t<_Range>>>, + __is_compatible_range<_Range>>, + typename = decltype(std::__adl_data(std::declval<_Range&>()))> constexpr span(_Range&& __range) noexcept(noexcept(::std::__adl_data(__range)) @@ -218,72 +241,77 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : span(::std::__adl_data(__range), ::std::__adl_size(__range)) { } - template<typename _ContiguousIterator, typename _Sentinel, - enable_if_t<!is_convertible_v<_Sentinel, index_type> - && __detail::__is_base_derived_safe_convertible_v< - remove_reference_t<typename - iterator_traits<_ContiguousIterator>::reference>, - element_type>>* = nullptr> + template<typename _ContiguousIterator, typename _Sentinel, typename + = _Require<__not_<is_convertible<_Sentinel, index_type>>, + __is_compatible_iterator<_ContiguousIterator>>> constexpr span(_ContiguousIterator __first, _Sentinel __last) - : span(::std::move(__first), static_cast<index_type>(__last - __first)) - { } + : _M_extent(static_cast<index_type>(__last - __first)), + _M_ptr(std::to_address(__first)) + { + if (_Extent != dynamic_extent) + __glibcxx_assert((__last - __first) == _Extent); + } - template<typename _ContiguousIterator> + template<typename _ContiguousIterator, typename + = _Require<__is_compatible_iterator<_ContiguousIterator>>> constexpr span(_ContiguousIterator __first, index_type __count) - noexcept(noexcept(::std::__adl_to_address(__first))) - : _M_extent(__count), _M_ptr(::std::__adl_to_address(__first)) + noexcept(noexcept(std::to_address(__first))) + : _M_extent(__count), _M_ptr(std::to_address(__first)) { __glibcxx_assert(_Extent == dynamic_extent || __count == _Extent); } - #else - + private: template<typename _Container, - enable_if_t< - (_Extent == dynamic_extent) - && !is_same_v<remove_cvref_t<_Container>, span> - && !__detail::__is_std_array_v<remove_cvref_t<_Container>> - && !is_array_v<remove_cvref_t<_Container>> - && __detail::__is_base_derived_safe_convertible_v< - remove_pointer_t<decltype( - ::std::__adl_data(::std::declval<_Container&>()) - + ::std::__adl_size(::std::declval<_Container&>()))>, - element_type>>* = nullptr> + typename _DataT = decltype(std::data(std::declval<_Container&>())), + typename _SizeT = decltype(std::size(std::declval<_Container&>()))> + using __is_compatible_container + = __is_compatible<remove_pointer_t<_DataT>>; + + public: + template<typename _Container, typename = _Require< + bool_constant<_Extent == dynamic_extent>, + __not_<__detail::__is_std_span<_Container>>, + __not_<__detail::__is_std_array<_Container>>, + __not_<is_array<_Container>>, + __is_compatible_container<_Container>>> constexpr - span(_Container& __range) - noexcept(noexcept(::std::__adl_data(__range)) - && noexcept(::std::__adl_size(__range))) - : span(::std::__adl_data(__range), ::std::__adl_size(__range)) + span(_Container& __cont) + noexcept(noexcept(std::data(__cont)) && noexcept(std::size(__cont))) + : _M_extent(std::size(__cont)), _M_ptr(std::data(__cont)) { } - template<typename _Container, - enable_if_t< - (_Extent == dynamic_extent) - && !is_same_v<remove_cvref_t<_Container>, span> - && !__detail::__is_std_array_v<remove_cvref_t<_Container>> - && !is_array_v<remove_cvref_t<_Container>> - && __detail::__is_base_derived_safe_convertible_v< - remove_pointer_t<decltype( - ::std::__adl_data(::std::declval<_Container&>()) - + ::std::__adl_size(::std::declval<_Container&>()))>, - element_type>>* = nullptr> - constexpr span(const _Container& __range) - noexcept(noexcept(::std::__adl_data(__range)) - && noexcept(::std::__adl_size(__range))) - : span(::std::__adl_data(__range), ::std::__adl_size(__range)) + template<typename _Container, typename = _Require< + bool_constant<_Extent == dynamic_extent>, + __not_<__detail::__is_std_span<_Container>>, + __not_<__detail::__is_std_array<_Container>>, + __not_<is_array<_Container>>, + __is_compatible_container<const _Container>>> + constexpr + span(const _Container& __cont) + noexcept(noexcept(std::data(__cont)) && noexcept(std::size(__cont))) + : _M_extent(std::size(__cont)), _M_ptr(std::data(__cont)) { } constexpr span(pointer __first, index_type __count) noexcept - : _M_extent(__count), _M_ptr(static_cast<pointer>(__first)) + : _M_extent(__count), _M_ptr(__first) { __glibcxx_assert(_Extent == dynamic_extent || __count == _Extent); } constexpr span(pointer __first, pointer __last) noexcept - : span(::std::move(__first), static_cast<index_type>(__last - __first)) + : span(__first, static_cast<index_type>(__last - __first)) { } #endif // P1394 + template<typename _OType, size_t _OExtent, typename = _Require< + __bool_constant<_Extent == dynamic_extent || _Extent == _OExtent>, + is_convertible<_OType(*)[], _Type(*)[]>>> + constexpr + span(const span<_OType, _OExtent>& __s) noexcept + : _M_extent(__s.size()), _M_ptr(__s.data()) + { } + // assignment constexpr span& @@ -474,7 +502,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION span(const array<_Type, _ArrayExtent>&) -> span<const _Type, _ArrayExtent>; -#if defined(_GLIBCXX_P1394) && _GLIBCXX_P1394 +#ifdef _GLIBCXX_P1394 template<typename _ContiguousIterator, typename _Sentinel> span(_ContiguousIterator, _Sentinel) |