[ PATCH ] C++20 <span>
JeanHeyd Meneide
phdofthehouse@gmail.com
Sat Aug 31 01:06:00 GMT 2019
Ahem -- we were supposed to use the 20 version of the constexpr macro,
not the base one.
I will note that, for some reason, the default constructor was already
constexpr, so we don't change that one!
On Fri, Aug 30, 2019 at 5:11 PM JeanHeyd Meneide
<phdofthehouse@gmail.com> wrote:
>
> On Fri, Aug 30, 2019 at 3:41 PM Jonathan Wakely <jwakely@redhat.com> wrote:
> >
> > On 30/08/19 15:22 -0400, JeanHeyd Meneide wrote:
> > >This patch implements <span> as it currently exists in the C++20 Working Draft.
> >
> > Nice!
> >
> >
> > >Notes:
> > >- __gnu_cxx::__normal_iterator is not fully constexpr, so its not used here
> >
> > I'd prefer to make __normal_iterator constexpr, and use it.
> > It needs to be constexpr anyway for string and vector.
> > ...
>
> Alright, thank you for the feedback. I fixed it up!
>
> Tested x86_64-pc-linux-gnu.
>
> 2019-08-30 JeanHeyd "ThePhD" Meneide <phdofthehouse@gmail.com>
>
> * include/std/span: Implement the entirety of span.
> * include/bits/stl_iterator.h: __gnu_cxx::__normal_iterator<T,
> C> is now constexpr-qualified for C++11+.
> * include/bits/range_access.h: Add __adl_* versions of access functions.
> * testsuite/23_containers/span/everything.cc: constexpr and
> non-constexpr tests.
> * include/Makefile.in: Add span to install.
> * include/Makefile.am: Likewise
-------------- next part --------------
diff --git a/.gitignore b/.gitignore
index d9d3967a12c..fd116c362ac 100644
--- a/.gitignore
+++ b/.gitignore
@@ -57,3 +57,7 @@ REVISION
/mpc*
/gmp*
/isl*
+
+# ignore sprinkled in dev files that keep popping up
+.vscode/
+.vs/
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index 3fe80f32cc4..b8b786d9260 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -68,6 +68,7 @@ std_headers = \
${std_srcdir}/scoped_allocator \
${std_srcdir}/set \
${std_srcdir}/shared_mutex \
+ ${std_srcdir}/span \
${std_srcdir}/sstream \
${std_srcdir}/stack \
${std_srcdir}/stdexcept \
diff --git a/libstdc++-v3/include/Makefile.in b/libstdc++-v3/include/Makefile.in
index b675d356cd4..cd1e9df5482 100644
--- a/libstdc++-v3/include/Makefile.in
+++ b/libstdc++-v3/include/Makefile.in
@@ -412,6 +412,7 @@ std_headers = \
${std_srcdir}/scoped_allocator \
${std_srcdir}/set \
${std_srcdir}/shared_mutex \
+ ${std_srcdir}/span \
${std_srcdir}/sstream \
${std_srcdir}/stack \
${std_srcdir}/stdexcept \
diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h
index d1e74711433..3acaebadcf1 100644
--- a/libstdc++-v3/include/bits/range_access.h
+++ b/libstdc++-v3/include/bits/range_access.h
@@ -318,6 +318,72 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++17
+#if __cplusplus > 201703L
+ // "why are these in namespace std:: and not __gnu_cxx:: ?"
+ // because if we don't put them here it's impossible to
+ // have implicit ADL with "using std::begin/end/size/data;".
+ template <typename _Container>
+ constexpr auto
+ __adl_begin(_Container& __cont) noexcept(noexcept(begin(__cont)))
+ { return begin(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_end(_Container& __cont) noexcept(noexcept(end(__cont)))
+ { return end(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_cbegin(_Container& __cont) noexcept(noexcept(cbegin(__cont)))
+ { return cbegin(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_cend(_Container& __cont) noexcept(noexcept(cend(__cont)))
+ { return cend(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_rbegin(_Container& __cont) noexcept(noexcept(rbegin(__cont)))
+ { return rbegin(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_rend(_Container& __cont) noexcept(noexcept(rend(__cont)))
+ { return rend(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_crbegin(_Container& __cont) noexcept(noexcept(crbegin(__cont)))
+ { return crbegin(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_crend(_Container& __cont) noexcept(noexcept(crend(__cont)))
+ { return crend(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_data(_Container& __cont) noexcept(noexcept(data(__cont)))
+ { return data(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_cdata(_Container& __cont) noexcept(noexcept(cdata(__cont)))
+ { return cdata(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_size(_Container& __cont) noexcept(noexcept(size(__cont)))
+ { return size(__cont); }
+
+ template <typename _Container>
+ constexpr auto
+ __adl_empty(_Container& __cont) noexcept(noexcept(empty(__cont)))
+ { return empty(__cont); }
+
+#endif // C++20
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 8ab0d72b0c2..f6a6060f2e3 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -799,55 +799,58 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typedef typename __traits_type::reference reference;
typedef typename __traits_type::pointer pointer;
+ // this was already constexpr
+ // so it will not be changed to
+ // _GLIBCXX_CONSTEXPR20
_GLIBCXX_CONSTEXPR __normal_iterator() _GLIBCXX_NOEXCEPT
: _M_current(_Iterator()) { }
explicit
- __normal_iterator(const _Iterator& __i) _GLIBCXX_NOEXCEPT
+ _GLIBCXX_CONSTEXPR20 __normal_iterator(const _Iterator& __i) _GLIBCXX_NOEXCEPT
: _M_current(__i) { }
// Allow iterator to const_iterator conversion
template<typename _Iter>
- __normal_iterator(const __normal_iterator<_Iter,
+ _GLIBCXX_CONSTEXPR20 __normal_iterator(const __normal_iterator<_Iter,
typename __enable_if<
(std::__are_same<_Iter, typename _Container::pointer>::__value),
_Container>::__type>& __i) _GLIBCXX_NOEXCEPT
: _M_current(__i.base()) { }
// Forward iterator requirements
- reference
+ _GLIBCXX_CONSTEXPR20 reference
operator*() const _GLIBCXX_NOEXCEPT
{ return *_M_current; }
- pointer
+ _GLIBCXX_CONSTEXPR20 pointer
operator->() const _GLIBCXX_NOEXCEPT
{ return _M_current; }
- __normal_iterator&
+ _GLIBCXX_CONSTEXPR20 __normal_iterator&
operator++() _GLIBCXX_NOEXCEPT
{
++_M_current;
return *this;
}
- __normal_iterator
+ _GLIBCXX_CONSTEXPR20 __normal_iterator
operator++(int) _GLIBCXX_NOEXCEPT
{ return __normal_iterator(_M_current++); }
// Bidirectional iterator requirements
- __normal_iterator&
+ _GLIBCXX_CONSTEXPR20 __normal_iterator&
operator--() _GLIBCXX_NOEXCEPT
{
--_M_current;
return *this;
}
- __normal_iterator
+ _GLIBCXX_CONSTEXPR20 __normal_iterator
operator--(int) _GLIBCXX_NOEXCEPT
{ return __normal_iterator(_M_current--); }
// Random access iterator requirements
- reference
+ _GLIBCXX_CONSTEXPR20 reference
operator[](difference_type __n) const _GLIBCXX_NOEXCEPT
{ return _M_current[__n]; }
@@ -855,19 +858,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
operator+=(difference_type __n) _GLIBCXX_NOEXCEPT
{ _M_current += __n; return *this; }
- __normal_iterator
+ _GLIBCXX_CONSTEXPR20 __normal_iterator
operator+(difference_type __n) const _GLIBCXX_NOEXCEPT
{ return __normal_iterator(_M_current + __n); }
- __normal_iterator&
+ _GLIBCXX_CONSTEXPR20 __normal_iterator&
operator-=(difference_type __n) _GLIBCXX_NOEXCEPT
{ _M_current -= __n; return *this; }
- __normal_iterator
+ _GLIBCXX_CONSTEXPR20 __normal_iterator
operator-(difference_type __n) const _GLIBCXX_NOEXCEPT
{ return __normal_iterator(_M_current - __n); }
- const _Iterator&
+ _GLIBCXX_CONSTEXPR20 const _Iterator&
base() const _GLIBCXX_NOEXCEPT
{ return _M_current; }
};
@@ -882,28 +885,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Forward iterator requirements
template<typename _IteratorL, typename _IteratorR, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() == __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator==(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() == __rhs.base(); }
template<typename _IteratorL, typename _IteratorR, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator!=(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() != __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator!=(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
@@ -911,56 +914,56 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Random access iterator requirements
template<typename _IteratorL, typename _IteratorR, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator<(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() < __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator<(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() < __rhs.base(); }
template<typename _IteratorL, typename _IteratorR, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator>(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() > __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator>(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() > __rhs.base(); }
template<typename _IteratorL, typename _IteratorR, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator<=(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() <= __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator<=(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() <= __rhs.base(); }
template<typename _IteratorL, typename _IteratorR, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator>=(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() >= __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline bool
+ _GLIBCXX_CONSTEXPR20 inline bool
operator>=(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
@@ -973,26 +976,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _IteratorL, typename _IteratorR, typename _Container>
#if __cplusplus >= 201103L
// DR 685.
- inline auto
+ _GLIBCXX_CONSTEXPR20 inline auto
operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs) noexcept
-> decltype(__lhs.base() - __rhs.base())
#else
- inline typename __normal_iterator<_IteratorL, _Container>::difference_type
+ _GLIBCXX_CONSTEXPR20 inline typename __normal_iterator<_IteratorL, _Container>::difference_type
operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
#endif
{ return __lhs.base() - __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline typename __normal_iterator<_Iterator, _Container>::difference_type
+ _GLIBCXX_CONSTEXPR20 inline typename __normal_iterator<_Iterator, _Container>::difference_type
operator-(const __normal_iterator<_Iterator, _Container>& __lhs,
const __normal_iterator<_Iterator, _Container>& __rhs)
_GLIBCXX_NOEXCEPT
{ return __lhs.base() - __rhs.base(); }
template<typename _Iterator, typename _Container>
- inline __normal_iterator<_Iterator, _Container>
+ _GLIBCXX_CONSTEXPR20 inline __normal_iterator<_Iterator, _Container>
operator+(typename __normal_iterator<_Iterator, _Container>::difference_type
__n, const __normal_iterator<_Iterator, _Container>& __i)
_GLIBCXX_NOEXCEPT
@@ -1006,7 +1009,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Iterator, typename _Container>
- _Iterator
+ _GLIBCXX_CONSTEXPR20 _Iterator
__niter_base(__gnu_cxx::__normal_iterator<_Iterator, _Container> __it)
_GLIBCXX_NOEXCEPT_IF(std::is_nothrow_copy_constructible<_Iterator>::value)
{ return __it.base(); }
diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span
new file mode 100644
index 00000000000..e4a30977585
--- /dev/null
+++ b/libstdc++-v3/include/std/span
@@ -0,0 +1,571 @@
+// Components for manipulating non-owning sequences of objects -*- C++ -*-
+
+// Copyright (C) 2019 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.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file span
+ * This is a Standard C++ Library header.
+ */
+
+//
+// P0122 span library
+// Contributed by ThePhD
+//
+
+#ifndef _GLIBCXX_SPAN
+#define _GLIBCXX_SPAN 1
+
+#pragma GCC system_header
+
+#if __cplusplus > 201703L
+
+#include <cstddef>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+#include <array>
+#include <bits/stl_iterator.h>
+#include <bits/range_access.h>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+ _GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+// FIXME: they forgot this feature test macro
+// get on someone's back about it in Belfast!!!
+#define __cpp_lib_span 201911
+
+ inline constexpr size_t dynamic_extent =
+ static_cast<size_t>(-1);
+
+ namespace __detail
+ {
+
+ template<typename _Element, typename _ToElement>
+ using __is_base_derived_safe_convertible =
+ is_convertible<_Element (*)[], _ToElement (*)[]>;
+
+ template<typename _Element, typename _ToElement>
+ static constexpr inline bool __is_base_derived_safe_convertible_v =
+ __is_base_derived_safe_convertible<_Element, _ToElement>::value;
+
+ template<typename>
+ struct __is_std_array : false_type
+ {
+ };
+
+ template<typename _Element, size_t _Extent>
+ struct __is_std_array<::std::array<_Element, _Extent>> : true_type
+ {
+ };
+
+#ifdef _GLIBCXX_DEBUG
+ template<typename _Element, size_t _Extent>
+ struct __is_std_array<::std::__debug::array<_Element, _Extent>>
+ : true_type
+ {
+ };
+#endif // debug/array
+
+ template<typename _Type>
+ inline constexpr bool __is_std_array_v = __is_std_array<_Type>::value;
+
+ template<size_t _Extent>
+ struct __extent_storage
+ {
+
+ constexpr __extent_storage() noexcept = default;
+ constexpr __extent_storage(size_t) noexcept
+ {
+ }
+
+ static constexpr size_t
+ _M_extent() noexcept
+ {
+ return _Extent;
+ }
+ };
+
+ template<>
+ struct __extent_storage<static_cast<size_t>(-1)>
+ {
+ size_t _M_extent_value;
+
+ constexpr __extent_storage() noexcept : _M_extent_value(0){};
+ constexpr __extent_storage(size_t __extent) noexcept
+ : _M_extent_value(__extent)
+ {
+ }
+
+ constexpr size_t
+ _M_extent() const noexcept
+ {
+ return this->_M_extent_value;
+ }
+ };
+
+ } // namespace __detail
+
+ template<typename _Type, size_t _Extent = dynamic_extent>
+ class span : private __detail::__extent_storage<_Extent>
+ {
+ public:
+ // member types
+ using value_type = remove_cv_t<_Type>;
+ using element_type = _Type;
+ using index_type = size_t;
+ using reference = element_type&;
+ using const_reference = const element_type&;
+ using pointer = _Type*;
+ using const_pointer = const _Type*;
+ using iterator = __gnu_cxx::__normal_iterator<pointer, span>;
+ using const_iterator = __gnu_cxx::__normal_iterator<const_pointer, span>;
+ using reverse_iterator = ::std::reverse_iterator<iterator>;
+ using const_reverse_iterator = ::std::reverse_iterator<const_iterator>;
+ using difference_type = ptrdiff_t;
+ // Official wording has no size_type -- why??
+ // using size_type = size_t;
+
+ // member constants
+ static inline constexpr size_t extent = _Extent;
+
+ private:
+ using __base_t = __detail::__extent_storage<_Extent>;
+
+ public:
+ // constructors
+ constexpr span() noexcept : __base_t(), _M_ptr(nullptr)
+ {
+ }
+
+ constexpr 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)
+ {
+ }
+
+ 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<array<value_type, _ArrayExtent>&>()))>,
+ element_type>>* = nullptr>
+ constexpr span(array<value_type, _ArrayExtent>& __arr) noexcept(
+ noexcept(::std::__adl_data(__arr)))
+ : span(::std::__adl_data(__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>
+ constexpr span(const array<value_type, _ArrayExtent>&
+ __arr) noexcept(noexcept(::std::__adl_data(__arr)))
+ : span(::std::__adl_data(__arr), _ArrayExtent)
+ {
+ }
+
+ // NOTE: when the time comes, and P1394 -
+ // range constructors for std::span - ships in
+ // the standard, delete the #else block and remove
+ // the conditional
+ // if the paper fails, delete #if block
+ // 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&>()))>,
+ element_type>>* = nullptr>
+ constexpr span(_Range&& __range) noexcept(
+ noexcept(::std::__adl_data(__range)) &&
+ noexcept(::std::__adl_size(__range)))
+ : 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>
+ constexpr span(_ContiguousIterator __first, _Sentinel __last)
+ : span(::std::move(__first), static_cast<index_type>(__last - __first))
+ {
+ }
+
+ template<typename _ContiguousIterator>
+ constexpr span(_ContiguousIterator __first, index_type __count) noexcept(
+ noexcept(::std::to_address(__first)))
+ : __base_t(__count), _M_ptr(::std::to_address(__first))
+ {
+ }
+#else
+ 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&>()))>,
+ element_type>>* = nullptr>
+ constexpr span(_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,
+ 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&>()))>,
+ 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))
+ {
+ }
+
+ constexpr span(pointer __first, pointer __last) noexcept
+ : span(::std::move(__first), static_cast<index_type>(__last - __first))
+ {
+ }
+ constexpr span(pointer __first, index_type __count) noexcept
+ : __base_t(__count), _M_ptr(static_cast<pointer>(__first))
+ {
+ }
+#endif // P1394
+
+ // assignment
+ constexpr span&
+ operator=(const span&) noexcept = default;
+
+ // observers
+ constexpr reference
+ front() noexcept
+ {
+ return *this->begin();
+ }
+
+ constexpr const_reference
+ front() const noexcept
+ {
+ return *this->begin();
+ }
+
+ constexpr reference
+ back() noexcept
+ {
+ return *(this->begin() + 1);
+ }
+
+ constexpr const_reference
+ back() const noexcept
+ {
+ return *(this->end() - 1);
+ }
+
+ constexpr reference operator[](index_type __idx) noexcept
+ {
+ return *(this->_M_ptr + __idx);
+ }
+
+ constexpr const_reference operator[](index_type __idx) const noexcept
+ {
+ return *(this->_M_ptr + __idx);
+ }
+
+ constexpr pointer
+ data() const noexcept
+ {
+ return this->_M_ptr;
+ }
+
+ constexpr index_type
+ size() const noexcept
+ {
+ return this->__base_t::_M_extent();
+ }
+
+ constexpr index_type
+ size_bytes() const noexcept
+ {
+ return this->__base_t::_M_extent() * sizeof(element_type);
+ }
+
+ constexpr bool
+ empty() const noexcept
+ {
+ return size() == 0;
+ }
+
+ // observers: iterators
+ constexpr iterator
+ begin() const noexcept
+ {
+ return iterator(this->_M_ptr);
+ }
+
+ constexpr const_iterator
+ cbegin() const noexcept
+ {
+ return const_iterator(this->_M_ptr);
+ }
+
+ constexpr iterator
+ end() const noexcept
+ {
+ return iterator(this->_M_ptr + this->size());
+ }
+
+ constexpr const_iterator
+ cend() const noexcept
+ {
+ return const_iterator(this->_M_ptr + this->size());
+ }
+
+ constexpr reverse_iterator
+ rbegin() const noexcept
+ {
+ return reverse_iterator(this->begin());
+ }
+
+ constexpr const_reverse_iterator
+ crbegin() const noexcept
+ {
+ return const_reverse_iterator(this->cbegin());
+ }
+
+ constexpr reverse_iterator
+ rend() const noexcept
+ {
+ return reverse_iterator(this->end());
+ }
+
+ constexpr const_reverse_iterator
+ crend() const noexcept
+ {
+ return const_reverse_iterator(this->cend());
+ }
+
+ // observers: subranges
+ template<size_t _Count>
+ constexpr auto
+ first() const
+ {
+ using __span_t = ::std::span<element_type, _Count>;
+ return __span_t(this->data(), _Count);
+ }
+
+ constexpr auto
+ first(index_type __count) const
+ {
+ using __span_t = ::std::span<element_type, dynamic_extent>;
+ return __span_t(this->data(), __count);
+ }
+
+ template<size_t _Count>
+ constexpr ::std::span<element_type, _Count>
+ last() const
+ {
+ static_assert(_Count == dynamic_extent ||
+ _Extent == dynamic_extent || _Count <= _Extent,
+ "assertion failed: Count or Extent are dynamic, "
+ "or the Count is less than the static extent");
+ using __span_t = ::std::span<element_type, _Count>;
+ return __span_t(this->data() + (this->size() - _Count), _Count);
+ }
+
+ constexpr auto
+ last(index_type __count) const
+ {
+ using __span_t = ::std::span<element_type, dynamic_extent>;
+ return __span_t(this->data() + (this->size() - __count), __count);
+ }
+
+ template<size_t _Offset,
+ size_t _Count = dynamic_extent>
+ constexpr auto
+ subspan() const
+ {
+ static_assert(_Count == dynamic_extent ||
+ _Extent == dynamic_extent ||
+ (_Offset + _Count) <= _Extent,
+ "assertion failed: Count or Extent are dynamic, "
+ "or the Count + Offset is less than the static extent");
+ constexpr size_t __span_extent =
+ (_Count != dynamic_extent
+ ? _Count
+ : (_Extent != dynamic_extent ? _Extent - _Offset
+ : dynamic_extent));
+ using __span_t = ::std::span<element_type, __span_extent>;
+ return __span_t(this->data() + _Offset,
+ (_Count == dynamic_extent ? this->size() - _Offset : _Count));
+ }
+
+ constexpr auto
+ subspan(
+ index_type __offset, index_type __count = dynamic_extent) const
+ {
+ using __span_t = ::std::span<element_type, dynamic_extent>;
+ return __span_t(this->data() + __offset,
+ __count == dynamic_extent ? this->size() - __offset : __count);
+ }
+
+ // observers: range helpers
+ friend constexpr iterator
+ begin(span __sp) noexcept
+ {
+ return __sp.begin();
+ }
+
+ friend constexpr iterator
+ end(span __sp) noexcept
+ {
+ return __sp.end();
+ }
+
+ private:
+ pointer _M_ptr;
+ };
+
+ template<typename _Type, size_t _Extent>
+ auto as_bytes(::std::span<_Type, _Extent> __sp) noexcept
+ {
+ constexpr size_t __byte_extent =
+ (_Extent == ::std::dynamic_extent
+ ? _Extent
+ : (_Extent *
+ sizeof(typename ::std::span<_Type, _Extent>::element_type)));
+ using __byte_span_t = ::std::span<const byte, __byte_extent>;
+ return __byte_span_t(
+ reinterpret_cast<const byte*>(__sp.data()), __sp.size_bytes());
+ }
+
+ template<typename _Type, size_t _Extent>
+ auto as_writable_bytes(::std::span<_Type, _Extent> __sp) noexcept
+ {
+ constexpr size_t __byte_extent =
+ (_Extent == dynamic_extent
+ ? _Extent
+ : (_Extent *
+ sizeof(typename ::std::span<_Type, _Extent>::element_type)));
+ using __byte_span_t = ::std::span<byte, __byte_extent>;
+ return __byte_span_t(
+ reinterpret_cast<byte*>(__sp.data()), __sp.size_bytes());
+ }
+
+ // tuple helpers
+ template<size_t _Index, typename _Type, size_t _Extent,
+ enable_if_t<(_Extent > 0) && (_Index < _Extent)>* = nullptr>
+ constexpr typename ::std::span<_Type, _Extent>::reference get(
+ ::std::span<_Type, _Extent> __sp) noexcept
+ {
+ return __sp[_Index];
+ }
+
+ template<typename _Type, size_t _Extent>
+ class tuple_size<::std::span<_Type, _Extent>>
+ : public integral_constant<size_t, _Extent>
+ {
+ };
+
+ template<typename _Type>
+ class tuple_size<::std::span<_Type, dynamic_extent>>;
+
+ template<size_t _Index, typename _Type, size_t _Extent>
+ struct tuple_element<_Index, ::std::span<_Type, _Extent>>
+ {
+ static_assert(_Index < _Extent, "assertion failed: Index is less than Extent");
+ using type = typename ::std::span<_Type, _Extent>::element_type;
+ };
+
+ // deduction guides
+ template<typename _Type, size_t _ArrayExtent>
+ span(_Type(&)[_ArrayExtent])->span<_Type, _ArrayExtent>;
+
+ template<typename _Type, size_t _ArrayExtent>
+ span(array<_Type, _ArrayExtent>&)->span<_Type, _ArrayExtent>;
+
+ template<typename _Type, size_t _ArrayExtent>
+ span(const array<_Type, _ArrayExtent>&)
+ ->span<const _Type, _ArrayExtent>;
+
+#if defined(_GLIBCXX_P1394) && _GLIBCXX_P1394
+
+ template<typename _ContiguousIterator, typename _Sentinel>
+ span(_ContiguousIterator, _Sentinel)
+ ->span<remove_reference_t<
+ typename iterator_traits<_ContiguousIterator>::reference>>;
+
+ template<typename _Range>
+ span(_Range &&)
+ ->span<remove_reference_t<typename iterator_traits<decltype(
+ ::std::__adl_begin(::std::declval<_Range&>()))>::reference>>;
+
+#else
+
+ template<typename _Container>
+ span(_Container&)->span<typename _Container::value_type>;
+
+ template<typename _Container>
+ span(const _Container&)->span<const typename _Container::value_type>;
+
+#endif // P1394
+
+ _GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std_GLIBCXX_VISIBILITY(default)
+
+#endif // C++20
+
+#endif
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index 7f7d05fd8f2..4341c9f0c1b 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -167,6 +167,9 @@
#define __cpp_lib_list_remove_return_type 201806L
#define __cpp_lib_math_constants 201907L
#define __cpp_lib_to_array 201907L
+// FIXME: they forgot this feature test macro
+// get on someone's back about it in Belfast!!!
+#define __cpp_lib_span 201911
#endif // C++2a
#endif // C++17
#endif // C++14
diff --git a/libstdc++-v3/testsuite/23_containers/span/everything.cc b/libstdc++-v3/testsuite/23_containers/span/everything.cc
new file mode 100644
index 00000000000..4a9ba442c68
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/span/everything.cc
@@ -0,0 +1,203 @@
+// Copyright (C) 2019 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=c++2a" }
+// { dg-do run { target c++2a } }
+
+#include <testsuite_hooks.h>
+
+#include <span>
+#include <type_traits>
+#include <cstdint>
+#include <vector>
+#include <algorithm>
+#include <cassert>
+
+int
+main()
+{
+ struct alignas(256) strawman
+ {
+ int x;
+ int y;
+ bool z;
+ int w;
+ };
+
+ struct naked_span
+ {
+ char* p;
+ std::size_t n;
+ };
+
+ struct strawman_span
+ {
+ strawman* p;
+ std::size_t n;
+ };
+
+ static_assert(sizeof(std::span<char, 0>) <= sizeof(char*));
+ static_assert(sizeof(std::span<const char, 0>) <= sizeof(const char*));
+ static_assert(sizeof(std::span<strawman, 0>) <= sizeof(strawman*));
+ static_assert(sizeof(std::span<strawman, 1>) <= sizeof(strawman*));
+ static_assert(sizeof(std::span<char>) <= sizeof(naked_span));
+ static_assert(sizeof(std::span<strawman>) <= sizeof(naked_span));
+
+ constexpr static std::array<int, 9> arr_data{ 0, 1, 2, 3, 4, 5, 6, 7, 8 };
+ constexpr auto arr_data_span = std::span(arr_data);
+ static_assert(arr_data_span.size() == 9);
+ static_assert(arr_data_span.size_bytes() == 9 * sizeof(int));
+ static_assert(*arr_data_span.begin() == 0);
+ static_assert(*arr_data_span.data() == 0);
+ static_assert(arr_data_span.front() == 0);
+ static_assert(arr_data_span.back() == 8);
+ static_assert(arr_data_span[0] == 0);
+ static_assert(arr_data_span[1] == 1);
+ static_assert(arr_data_span[2] == 2);
+ static_assert(arr_data_span[3] == 3);
+ static_assert(arr_data_span[4] == 4);
+ static_assert(arr_data_span[5] == 5);
+ static_assert(arr_data_span[6] == 6);
+ static_assert(arr_data_span[7] == 7);
+ static_assert(arr_data_span[8] == 8);
+ static_assert(!arr_data_span.empty());
+ static_assert(decltype(arr_data_span)::extent == 9);
+
+ constexpr static int data[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8 };
+ constexpr auto data_span = std::span(data);
+ static_assert(data_span.size() == 9);
+ static_assert(data_span.size_bytes() == 9 * sizeof(int));
+ static_assert(*data_span.begin() == 0);
+ static_assert(*data_span.data() == 0);
+ static_assert(data_span.front() == 0);
+ static_assert(data_span.back() == 8);
+ static_assert(data_span[0] == 0);
+ static_assert(data_span[1] == 1);
+ static_assert(data_span[2] == 2);
+ static_assert(data_span[3] == 3);
+ static_assert(data_span[4] == 4);
+ static_assert(data_span[5] == 5);
+ static_assert(data_span[6] == 6);
+ static_assert(data_span[7] == 7);
+ static_assert(data_span[8] == 8);
+ static_assert(!data_span.empty());
+ static_assert(decltype(data_span)::extent == 9);
+
+ constexpr auto data_span_first = data_span.first<3>();
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_first)>, std::span<const int, 3>>);
+ static_assert(decltype(data_span_first)::extent == 3);
+ static_assert(data_span_first.size() == 3);
+ static_assert(data_span_first.front() == 0);
+ static_assert(data_span_first.back() == 2);
+ static_assert(std::tuple_size_v<decltype(data_span_first)> == 3);
+ static_assert(std::is_same_v<std::tuple_element_t<0, decltype(data_span_first)>, const int>);
+
+ constexpr auto data_span_first_dyn = data_span.first(4);
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_first_dyn)>, std::span<const int>>);
+ static_assert(decltype(data_span_first_dyn)::extent == std::dynamic_extent);
+ static_assert(data_span_first_dyn.size() == 4);
+ static_assert(data_span_first_dyn.front() == 0);
+ static_assert(data_span_first_dyn.back() == 3);
+
+ constexpr auto data_span_last = data_span.last<5>();
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_last)>, std::span<const int, 5>>);
+ static_assert(decltype(data_span_last)::extent == 5);
+ static_assert(data_span_last.size() == 5);
+ static_assert(data_span_last.front() == 4);
+ static_assert(data_span_last.back() == 8);
+ static_assert(std::tuple_size_v<decltype(data_span_last)> == 5);
+ static_assert(std::is_same_v<std::tuple_element_t<0, decltype(data_span_last)>, const int>);
+
+ constexpr auto data_span_last_dyn = data_span.last(6);
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_last_dyn)>, std::span<const int>>);
+ static_assert(decltype(data_span_last_dyn)::extent == std::dynamic_extent);
+ static_assert(data_span_last_dyn.size() == 6);
+ static_assert(data_span_last_dyn.front() == 3);
+ static_assert(data_span_last_dyn.back() == 8);
+
+ constexpr auto data_span_subspan = data_span.subspan<1, 3>();
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_subspan)>, std::span<const int, 3>>);
+ static_assert(decltype(data_span_subspan)::extent == 3);
+ static_assert(data_span_subspan.size() == 3);
+ static_assert(data_span_subspan.front() == 1);
+ static_assert(data_span_subspan.back() == 3);
+
+ constexpr auto data_span_subspan_offset = data_span.subspan<8>();
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_subspan_offset)>, std::span<const int, 1>>);
+ static_assert(decltype(data_span_subspan_offset)::extent == 1);
+ static_assert(data_span_subspan_offset.size() == 1);
+ static_assert(data_span_subspan_offset.front() == 8);
+ static_assert(data_span_subspan_offset.back() == 8);
+
+ constexpr auto data_span_subspan_empty = data_span.subspan(9, 0);
+ static_assert(
+ std::is_same_v<std::remove_cv_t<decltype(data_span_subspan_empty)>, std::span<const int>>);
+ static_assert(decltype(data_span_subspan_empty)::extent == std::dynamic_extent);
+ static_assert(data_span_subspan_empty.size() == 0);
+
+ constexpr auto data_span_subspan_empty_static = data_span.subspan<9>();
+ static_assert(std::is_same_v<std::remove_cv_t<decltype(data_span_subspan_empty_static)>,
+ std::span<const int, 0>>);
+ static_assert(decltype(data_span_subspan_empty_static)::extent == 0);
+ static_assert(data_span_subspan_empty.size() == 0);
+
+ std::span<short> shorts{};
+ bool really_empty0 = shorts.empty();
+ bool really_empty1 = std::empty(shorts);
+ bool really_empty2 = shorts.data() == nullptr;
+ bool really_empty3 = shorts.begin() == shorts.end();
+ bool really_empty4 = shorts.cbegin() == shorts.cend();
+ bool really_empty =
+ really_empty0 && really_empty1 && really_empty2 && really_empty3 && really_empty4;
+ (void)really_empty;
+ VERIFY(really_empty);
+
+ std::vector<std::int_least32_t> value{ 0 };
+ std::span<int32_t> muh_span(value);
+ VERIFY(muh_span.size() == 1);
+ std::byte* original_bytes = reinterpret_cast<std::byte*>(value.data());
+ original_bytes[0] = static_cast<std::byte>(1);
+ original_bytes[1] = static_cast<std::byte>(2);
+ original_bytes[2] = static_cast<std::byte>(3);
+ original_bytes[3] = static_cast<std::byte>(4);
+ std::span<const std::byte> muh_byte_span = std::as_bytes(muh_span);
+ std::span<std::byte> muh_mutable_byte_span = std::as_writable_bytes(muh_span);
+ std::span<std::byte> muh_original_byte_span(original_bytes, original_bytes + 4);
+ bool definitely_reinterpret_casted0 = std::equal(muh_byte_span.cbegin(), muh_byte_span.cend(),
+ muh_original_byte_span.cbegin(), muh_original_byte_span.cend());
+ bool definitely_reinterpret_casted1 = std::equal(muh_mutable_byte_span.cbegin(),
+ muh_mutable_byte_span.cend(), muh_original_byte_span.cbegin(), muh_original_byte_span.cend());
+ bool definitely_reinterpret_casted =
+ definitely_reinterpret_casted0 && definitely_reinterpret_casted1;
+ (void)definitely_reinterpret_casted;
+ VERIFY(definitely_reinterpret_casted);
+
+ std::span<std::byte> muh_original_byte_span_ptr_size(original_bytes, 4);
+ bool definitely_equivalent =
+ std::equal(muh_original_byte_span_ptr_size.cbegin(), muh_original_byte_span_ptr_size.cend(),
+ muh_original_byte_span.cbegin(), muh_original_byte_span.cend());
+ (void)definitely_equivalent;
+ VERIFY(definitely_equivalent);
+
+ return definitely_equivalent && definitely_reinterpret_casted && really_empty ? 0 : 1;
+}
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