Commit 9b8e2dea by Jonathan Wakely

libstdc++: P1976R2 Fixed-size span construction from dynamic range

This includes fixes for first, last, as_bytes and as_writable_bytes
which were missing from the paper.

	* include/std/span (__cpp_lib_span): Update value.
	(span(It, size_type), span(It, End)): Make conditionally explicit. Add
	assertion.
	(span(R&&), span(const span<OType, OExtent>&)): Likewise and relax
	constraints.
	(span::first<Count>(), span::last<Count>()): Use explicit type in
	return statement.
	(as_bytes, as_writable_bytes): Likewise.
	* include/std/version (__cpp_lib_span): Update value.
	* testsuite/23_containers/span/1.cc: Check new value.
	* testsuite/23_containers/span/2.cc: Check new value.
	* testsuite/23_containers/span/explicit.cc: New test.
parent d6c9e372
2020-02-18 Jonathan Wakely <jwakely@redhat.com> 2020-02-18 Jonathan Wakely <jwakely@redhat.com>
P1976R2 Fixed-size span construction from dynamic range
* include/std/span (__cpp_lib_span): Update value.
(span(It, size_type), span(It, End)): Make conditionally explicit. Add
assertion.
(span(R&&), span(const span<OType, OExtent>&)): Likewise and relax
constraints.
(span::first<Count>(), span::last<Count>()): Use explicit type in
return statement.
(as_bytes, as_writable_bytes): Likewise.
* include/std/version (__cpp_lib_span): Update value.
* testsuite/23_containers/span/1.cc: Check new value.
* testsuite/23_containers/span/2.cc: Check new value.
* testsuite/23_containers/span/explicit.cc: New test.
* include/std/span (span::__is_compatible_array): Simplify alias * include/std/span (span::__is_compatible_array): Simplify alias
template by using requires-clause. template by using requires-clause.
(span::__is_compatible_ref): New alias template for constraining (span::__is_compatible_ref): New alias template for constraining
......
...@@ -48,7 +48,7 @@ namespace std _GLIBCXX_VISIBILITY(default) ...@@ -48,7 +48,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
{ {
_GLIBCXX_BEGIN_NAMESPACE_VERSION _GLIBCXX_BEGIN_NAMESPACE_VERSION
#define __cpp_lib_span 201902L #define __cpp_lib_span 202002L
inline constexpr size_t dynamic_extent = static_cast<size_t>(-1); inline constexpr size_t dynamic_extent = static_cast<size_t>(-1);
...@@ -158,23 +158,30 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -158,23 +158,30 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<contiguous_iterator _It> template<contiguous_iterator _It>
requires __is_compatible_ref<iter_reference_t<_It>>::value requires __is_compatible_ref<iter_reference_t<_It>>::value
constexpr constexpr explicit(extent != dynamic_extent)
span(_It __first, size_type __count) span(_It __first, size_type __count)
noexcept noexcept
: _M_extent(__count), _M_ptr(std::to_address(__first)) : _M_extent(__count), _M_ptr(std::to_address(__first))
{ __glibcxx_assert(_Extent == dynamic_extent || __count == _Extent); } {
if constexpr (_Extent != dynamic_extent)
{
__glibcxx_assert(__count == _Extent);
}
}
template<contiguous_iterator _It, sized_sentinel_for<_It> _End> template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
requires __is_compatible_ref<iter_reference_t<_It>>::value requires __is_compatible_ref<iter_reference_t<_It>>::value
&& (!is_convertible_v<_End, size_type>) && (!is_convertible_v<_End, size_type>)
constexpr constexpr explicit(extent != dynamic_extent)
span(_It __first, _End __last) span(_It __first, _End __last)
noexcept(noexcept(__last - __first)) noexcept(noexcept(__last - __first))
: _M_extent(static_cast<size_type>(__last - __first)), : _M_extent(static_cast<size_type>(__last - __first)),
_M_ptr(std::to_address(__first)) _M_ptr(std::to_address(__first))
{ {
if (_Extent != dynamic_extent) if constexpr (_Extent != dynamic_extent)
__glibcxx_assert((__last - __first) == _Extent); {
__glibcxx_assert((__last - __first) == _Extent);
}
} }
template<typename _Tp, size_t _ArrayExtent> template<typename _Tp, size_t _ArrayExtent>
...@@ -199,30 +206,41 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -199,30 +206,41 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ } { }
template<typename _Range> template<typename _Range>
requires (_Extent == dynamic_extent) requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
&& ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
&& (ranges::safe_range<_Range> || is_const_v<element_type>) && (ranges::safe_range<_Range> || is_const_v<element_type>)
&& (!__detail::__is_std_span<remove_cvref_t<_Range>>::value) && (!__detail::__is_std_span<remove_cvref_t<_Range>>::value)
&& (!__detail::__is_std_array<remove_cvref_t<_Range>>::value) && (!__detail::__is_std_array<remove_cvref_t<_Range>>::value)
&& (!is_array_v<remove_cvref_t<_Range>>) && (!is_array_v<remove_cvref_t<_Range>>)
&& __is_compatible_ref<ranges::range_reference_t<_Range>>::value && __is_compatible_ref<ranges::range_reference_t<_Range>>::value
constexpr constexpr explicit(extent != dynamic_extent)
span(_Range&& __range) span(_Range&& __range)
noexcept(noexcept(ranges::data(__range)) noexcept(noexcept(ranges::data(__range))
&& noexcept(ranges::size(__range))) && noexcept(ranges::size(__range)))
: span(ranges::data(__range), ranges::size(__range)) : span(ranges::data(__range), ranges::size(__range))
{ } {
if constexpr (extent != dynamic_extent)
{
__glibcxx_assert(ranges::size(__range) == extent);
}
}
constexpr constexpr
span(const span&) noexcept = default; span(const span&) noexcept = default;
template<typename _OType, size_t _OExtent> template<typename _OType, size_t _OExtent>
requires (_Extent == dynamic_extent || _Extent == _OExtent) requires (_Extent == dynamic_extent || _OExtent == dynamic_extent
|| _Extent == _OExtent)
&& (__is_array_convertible<_Type, _OType>::value) && (__is_array_convertible<_Type, _OType>::value)
constexpr constexpr
explicit(extent != dynamic_extent && _OExtent == dynamic_extent)
span(const span<_OType, _OExtent>& __s) noexcept span(const span<_OType, _OExtent>& __s) noexcept
: _M_extent(__s.size()), _M_ptr(__s.data()) : _M_extent(__s.size()), _M_ptr(__s.data())
{ } {
if constexpr (extent != dynamic_extent)
{
__glibcxx_assert(__s.size() == extent);
}
}
~span() noexcept = default; ~span() noexcept = default;
...@@ -317,7 +335,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -317,7 +335,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__glibcxx_assert(_Count <= size()); __glibcxx_assert(_Count <= size());
else else
static_assert(_Count <= extent); static_assert(_Count <= extent);
return { this->data(), _Count }; using _Sp = span<element_type, _Count>;
return _Sp{ this->data(), _Count };
} }
constexpr span<element_type, dynamic_extent> constexpr span<element_type, dynamic_extent>
...@@ -335,7 +354,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -335,7 +354,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__glibcxx_assert(_Count <= size()); __glibcxx_assert(_Count <= size());
else else
static_assert(_Count <= extent); static_assert(_Count <= extent);
return { this->data() + (this->size() - _Count), _Count }; using _Sp = span<element_type, _Count>;
return _Sp{ this->data() + (this->size() - _Count), _Count };
} }
constexpr span<element_type, dynamic_extent> constexpr span<element_type, dynamic_extent>
...@@ -351,12 +371,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -351,12 +371,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
-> span<element_type, _S_subspan_extent<_Offset, _Count>()> -> span<element_type, _S_subspan_extent<_Offset, _Count>()>
{ {
if constexpr (_Extent == dynamic_extent) if constexpr (_Extent == dynamic_extent)
__glibcxx_assert(_Offset <= size()); {
__glibcxx_assert(_Offset <= size());
}
else else
static_assert(_Offset <= extent); static_assert(_Offset <= extent);
using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>;
if constexpr (_Count == dynamic_extent) if constexpr (_Count == dynamic_extent)
return { this->data() + _Offset, this->size() - _Offset }; return _Sp{ this->data() + _Offset, this->size() - _Offset };
else else
{ {
if constexpr (_Extent == dynamic_extent) if constexpr (_Extent == dynamic_extent)
...@@ -369,7 +393,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -369,7 +393,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static_assert(_Count <= extent); static_assert(_Count <= extent);
static_assert(_Count <= (extent - _Offset)); static_assert(_Count <= (extent - _Offset));
} }
return { this->data() + _Offset, _Count }; return _Sp{ this->data() + _Offset, _Count };
} }
} }
...@@ -419,7 +443,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -419,7 +443,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
? dynamic_extent : _Extent * sizeof(_Type)> ? dynamic_extent : _Extent * sizeof(_Type)>
as_bytes(span<_Type, _Extent> __sp) noexcept as_bytes(span<_Type, _Extent> __sp) noexcept
{ {
return {reinterpret_cast<const byte*>(__sp.data()), __sp.size_bytes()}; auto data = reinterpret_cast<const byte*>(__sp.data());
auto size = __sp.size_bytes();
constexpr auto extent = _Extent == dynamic_extent
? dynamic_extent : _Extent * sizeof(_Type);
return span<const byte, extent>{data, size};
} }
template<typename _Type, size_t _Extent> template<typename _Type, size_t _Extent>
...@@ -428,7 +456,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION ...@@ -428,7 +456,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
? dynamic_extent : _Extent * sizeof(_Type)> ? dynamic_extent : _Extent * sizeof(_Type)>
as_writable_bytes(span<_Type, _Extent> __sp) noexcept as_writable_bytes(span<_Type, _Extent> __sp) noexcept
{ {
return {reinterpret_cast<byte*>(__sp.data()), __sp.size_bytes()}; auto data = reinterpret_cast<byte*>(__sp.data());
auto size = __sp.size_bytes();
constexpr auto extent = _Extent == dynamic_extent
? dynamic_extent : _Extent * sizeof(_Type);
return span<byte, extent>{data, size};
} }
namespace ranges namespace ranges
......
...@@ -193,7 +193,7 @@ ...@@ -193,7 +193,7 @@
#endif #endif
#define __cpp_lib_list_remove_return_type 201806L #define __cpp_lib_list_remove_return_type 201806L
#define __cpp_lib_math_constants 201907L #define __cpp_lib_math_constants 201907L
#define __cpp_lib_span 201902L #define __cpp_lib_span 202002L
#if __cpp_impl_three_way_comparison >= 201907L && __cpp_lib_concepts #if __cpp_impl_three_way_comparison >= 201907L && __cpp_lib_concepts
# define __cpp_lib_three_way_comparison 201711L # define __cpp_lib_three_way_comparison 201711L
#endif #endif
......
...@@ -22,6 +22,6 @@ ...@@ -22,6 +22,6 @@
#ifndef __cpp_lib_span #ifndef __cpp_lib_span
# error "Feature-test macro for span missing in <span>" # error "Feature-test macro for span missing in <span>"
#elif __cpp_lib_span != 201902L #elif __cpp_lib_span != 202002L
# error "Feature-test macro for span has wrong value in <span>" # error "Feature-test macro for span has wrong value in <span>"
#endif #endif
...@@ -22,6 +22,6 @@ ...@@ -22,6 +22,6 @@
#ifndef __cpp_lib_span #ifndef __cpp_lib_span
# error "Feature-test macro for span missing in <version>" # error "Feature-test macro for span missing in <version>"
#elif __cpp_lib_span != 201902L #elif __cpp_lib_span != 202002L
# error "Feature-test macro for span has wrong value in <version>" # error "Feature-test macro for span has wrong value in <version>"
#endif #endif
// Copyright (C) 2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++2a" }
// { dg-do compile { target c++2a } }
#include <span>
struct Range
{
int* begin();
int* end();
unsigned size() const;
} r;
auto first = std::begin(r), last = std::end(r);
// span(It, size_type)
std::span<int> s1 = {first, 2};
std::span<int, 2> s2 = {first, 2}; // { dg-error "could not convert" }
// span(It, End)
std::span<int> s3 = {first, last};
std::span<int, 2> s4 = {first, last}; // { dg-error "could not convert" }
// span(R&&)
std::span<int> s5 = r;
std::span<int, 2> s6 = r; // { dg-error "conversion from" }
// span(const span<OtherElement, OtherExtent>&)
std::span<const int> s7 = s5;
std::span<const int> s8 = s6;
std::span<const int, 1> s9 = s5.first(1); // { dg-error "conversion from" }
std::span<const int, 1> s10 = s7.first(1); // { dg-error "conversion from" }
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