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| author | Jonathan Wakely <jwakely@redhat.com> | 2019-09-30 12:52:08 +0100 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2019-09-30 12:52:08 +0100 |
| commit | 582c57a17eaf02e90492145cd7217bda5499076b (patch) | |
| tree | 2c75c44849d88b4261c0cf454cf0118a4534976e /libstdc++-v3/include/std/span | |
| parent | 6438d29fb1a31c95b9d652117a79dde2f9e4ad6f (diff) | |
| download | gcc-582c57a17eaf02e90492145cd7217bda5499076b.zip gcc-582c57a17eaf02e90492145cd7217bda5499076b.tar.gz gcc-582c57a17eaf02e90492145cd7217bda5499076b.tar.bz2 | |
Implement LWG 3255 for std::span constructors
Also fix the constraints on span(Container&) and span(const Container&)
constructors so that they aren't used for const spans or const arrays.
* include/std/span (span(element_type(&)[N]))
(span(array<value_type, N>&), span(const array<value_type, N>&)):
Deduce array element type to allow safe const conversions (LWG 3255).
[!_GLIBCXX_P1394] (span(Container&), span(const Container&)): Use
remove_cv_t on arguments to __is_std_span and __is_std_array.
* testsuite/23_containers/span/lwg3255.cc: New test.
From-SVN: r276298
Diffstat (limited to 'libstdc++-v3/include/std/span')
| -rw-r--r-- | libstdc++-v3/include/std/span | 45 |
1 files changed, 24 insertions, 21 deletions
diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span index 1a0d61c..fcec22a 100644 --- a/libstdc++-v3/include/std/span +++ b/libstdc++-v3/include/std/span @@ -125,6 +125,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Tp> using __is_compatible = is_convertible<_Tp(*)[], _Type(*)[]>; + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3255. span's array constructor is too strict + template<typename _Tp, size_t _ArrayExtent, + typename = enable_if_t<_Extent == dynamic_extent + || _ArrayExtent == _Extent>> + using __is_compatible_array = __is_compatible<_Tp>; + public: // member types using value_type = remove_cv_t<_Type>; @@ -149,9 +156,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // constructors - template <typename _Dummy = _Type, - enable_if_t<is_same_v<_Dummy, _Type> - && (_Extent == dynamic_extent || _Extent == 0)>* = nullptr> + template<bool _DefaultConstructible = (_Extent + 1u) <= 1u, + enable_if_t<_DefaultConstructible>* = nullptr> constexpr span() noexcept : _M_extent(0), _M_ptr(nullptr) { } @@ -159,28 +165,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION constexpr span(const span&) noexcept = default; - template<size_t _ArrayExtent, - enable_if_t<_Extent == dynamic_extent || _ArrayExtent == _Extent>* - = nullptr> + template<typename _Tp, size_t _ArrayExtent, + typename = _Require<__is_compatible_array<_Tp, _ArrayExtent>>> constexpr - span(element_type (&__arr)[_ArrayExtent]) noexcept + span(_Tp (&__arr)[_ArrayExtent]) noexcept : span(static_cast<pointer>(__arr), _ArrayExtent) { } - template<size_t _ArrayExtent, - enable_if_t<_Extent == dynamic_extent || _ArrayExtent == _Extent>* - = nullptr> + template<typename _Tp, size_t _ArrayExtent, + typename = _Require<__is_compatible_array<_Tp, _ArrayExtent>>> constexpr - span(array<value_type, _ArrayExtent>& __arr) noexcept - : span(__arr.data(), _ArrayExtent) + span(array<_Tp, _ArrayExtent>& __arr) noexcept + : span(static_cast<pointer>(__arr.data()), _ArrayExtent) { } - template<size_t _ArrayExtent, - enable_if_t<_Extent == dynamic_extent || _ArrayExtent == _Extent>* - = nullptr> + template<typename _Tp, size_t _ArrayExtent, + typename = _Require<__is_compatible_array<_Tp, _ArrayExtent>>> constexpr - span(const array<value_type, _ArrayExtent>& __arr) noexcept - : span(__arr.data(), _ArrayExtent) + span(const array<_Tp, _ArrayExtent>& __arr) noexcept + : span(static_cast<pointer>(__arr.data()), _ArrayExtent) { } // NOTE: when the time comes, and P1394 - @@ -271,8 +274,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION public: template<typename _Container, typename = _Require< bool_constant<_Extent == dynamic_extent>, - __not_<__detail::__is_std_span<_Container>>, - __not_<__detail::__is_std_array<_Container>>, + __not_<__detail::__is_std_span<remove_cv_t<_Container>>>, + __not_<__detail::__is_std_array<remove_cv_t<_Container>>>, __not_<is_array<_Container>>, __is_compatible_container<_Container>>> constexpr @@ -283,8 +286,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Container, typename = _Require< bool_constant<_Extent == dynamic_extent>, - __not_<__detail::__is_std_span<_Container>>, - __not_<__detail::__is_std_array<_Container>>, + __not_<__detail::__is_std_span<remove_cv_t<_Container>>>, + __not_<__detail::__is_std_array<remove_cv_t<_Container>>>, __not_<is_array<_Container>>, __is_compatible_container<const _Container>>> constexpr |