On Thu, 10 Feb 2022, Patrick Palka wrote:
> Tested on x86_64-pc-linux-gnu, does this look OK for the 11 branch?
> The backport to the 10 branch hasn't been started yet, I figured it'd
> be good to first get the 11 backport right then base the 10 backport
> on the 11 one.
>
> NB: This backport of r12-1606 to the 11 branch deliberately omits parts
> of P2325R3 so as to maximize backward compatibility with pre-P2325R3 code.
> In particular, we don't remove the default ctors for back_insert_iterator,
> front_insert_iterator, ostream_iterator, ref_view and basic_istream_view.
FWIW here's a diff of the changes in this backport relative to r12-1606:
libstdc++-v3/include/bits/stl_iterator.h | 13 ++++++++++-
libstdc++-v3/include/bits/stream_iterator.h | 5 +++++
libstdc++-v3/include/std/ranges | 24 +++++++++++++++------
.../24_iterators/back_insert_iterator/constexpr.cc | 3 ++-
.../front_insert_iterator/constexpr.cc | 3 ++-
.../ostream_iterator/requirements/constexpr.cc | 24 +++++++++++++++++++++
libstdc++-v3/testsuite/std/ranges/97600.cc | 3 ++-
libstdc++-v3/testsuite/std/ranges/p2325.cc | 25 ++++++++++++++++++++++
8 files changed, 89 insertions(+), 11 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_iterator.h
b/libstdc++-v3/include/bits/stl_iterator.h
index 7fe727d8093..549bc26dee5 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -639,6 +639,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typedef _Container container_type;
#if __cplusplus > 201703L
using difference_type = ptrdiff_t;
+
+ constexpr back_insert_iterator() noexcept : container(nullptr) { }
#endif
/// The only way to create this %iterator is with a container.
@@ -740,6 +742,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typedef _Container container_type;
#if __cplusplus > 201703L
using difference_type = ptrdiff_t;
+
+ constexpr front_insert_iterator() noexcept : container(nullptr) { }
#endif
/// The only way to create this %iterator is with a container.
@@ -839,12 +843,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
#if __cplusplus > 201703L && defined __cpp_lib_concepts
using _Iter = std::__detail::__range_iter_t<_Container>;
+
+ protected:
+ _Container* container = nullptr;
+ _Iter iter = _Iter();
#else
typedef typename _Container::iterator _Iter;
-#endif
+
protected:
_Container* container;
_Iter iter;
+#endif
public:
/// A nested typedef for the type of whatever container you used.
@@ -852,6 +861,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus > 201703L && defined __cpp_lib_concepts
using difference_type = ptrdiff_t;
+
+ insert_iterator() = default;
#endif
/**
diff --git a/libstdc++-v3/include/bits/stream_iterator.h
b/libstdc++-v3/include/bits/stream_iterator.h
index d07474d4996..fd8920b8d01 100644
--- a/libstdc++-v3/include/bits/stream_iterator.h
+++ b/libstdc++-v3/include/bits/stream_iterator.h
@@ -192,6 +192,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
const _CharT* _M_string;
public:
+#if __cplusplus > 201703L
+ constexpr ostream_iterator() noexcept
+ : _M_stream(nullptr), _M_string(nullptr) { }
+#endif
+
/// Construct from an ostream.
ostream_iterator(ostream_type& __s)
: _M_stream(std::__addressof(__s)), _M_string(0) {}
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index a01b5e79f1f..bf6cfae2a6e 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -680,6 +680,8 @@ namespace views
: public view_interface<basic_istream_view<_Val, _CharT, _Traits>>
{
public:
+ basic_istream_view() = default;
+
constexpr explicit
basic_istream_view(basic_istream<_CharT, _Traits>& __stream)
: _M_stream(std::__addressof(__stream))
@@ -688,7 +690,8 @@ namespace views
constexpr auto
begin()
{
- *_M_stream >> _M_object;
+ if (_M_stream != nullptr)
+ *_M_stream >> _M_object;
return _Iterator{this};
}
@@ -697,8 +700,8 @@ namespace views
{ return default_sentinel; }
private:
- basic_istream<_CharT, _Traits>* _M_stream;
- _Val _M_object;
+ basic_istream<_CharT, _Traits>* _M_stream = nullptr;
+ _Val _M_object = _Val();
struct _Iterator
{
@@ -720,6 +723,7 @@ namespace views
_Iterator&
operator++()
{
+ __glibcxx_assert(_M_parent->_M_stream != nullptr);
*_M_parent->_M_stream >> _M_parent->_M_object;
return *this;
}
@@ -730,18 +734,21 @@ namespace views
_Val&
operator*() const
- { return _M_parent->_M_object; }
+ {
+ __glibcxx_assert(_M_parent->_M_stream != nullptr);
+ return _M_parent->_M_object;
+ }
friend bool
operator==(const _Iterator& __x, default_sentinel_t)
{ return __x._M_at_end(); }
private:
- basic_istream_view* _M_parent;
+ basic_istream_view* _M_parent = nullptr;
bool
_M_at_end() const
- { return !*_M_parent->_M_stream; }
+ { return _M_parent == nullptr || !*_M_parent->_M_stream; }
};
friend _Iterator;
@@ -1045,12 +1052,15 @@ namespace views::__adaptor
class ref_view : public view_interface<ref_view<_Range>>
{
private:
- _Range* _M_r;
+ _Range* _M_r = nullptr;
static void _S_fun(_Range&); // not defined
static void _S_fun(_Range&&) = delete;
public:
+ constexpr
+ ref_view() noexcept = default;
+
template<__detail::__not_same_as<ref_view> _Tp>
requires convertible_to<_Tp, _Range&>
&& requires { _S_fun(declval<_Tp>()); }
diff --git
a/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/constexpr.cc
b/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/constexpr.cc
index 27acd071df1..bef2289ba79 100644
--- a/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/constexpr.cc
+++ b/libstdc++-v3/testsuite/24_iterators/back_insert_iterator/constexpr.cc
@@ -42,7 +42,8 @@ constexpr bool
test01()
{
container c;
- std::back_insert_iterator<container> iter = std::back_inserter(c);
+ std::back_insert_iterator<container> iter;
+ iter = std::back_inserter(c);
*iter++ = 1;
int i = 2;
*iter = i;
diff --git
a/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/constexpr.cc
b/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/constexpr.cc
index cff7f6a4524..7b4c990b107 100644
--- a/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/constexpr.cc
+++ b/libstdc++-v3/testsuite/24_iterators/front_insert_iterator/constexpr.cc
@@ -42,7 +42,8 @@ constexpr bool
test01()
{
container c;
- std::front_insert_iterator<container> iter = std::front_inserter(c);
+ std::front_insert_iterator<container> iter;
+ iter = std::front_inserter(c);
*iter++ = 1;
int i = 2;
*iter = i;
diff --git
a/libstdc++-v3/testsuite/24_iterators/ostream_iterator/requirements/constexpr.cc
b/libstdc++-v3/testsuite/24_iterators/ostream_iterator/requirements/constexpr.cc
new file mode 100644
index 00000000000..4edaaa8aebb
--- /dev/null
+++
b/libstdc++-v3/testsuite/24_iterators/ostream_iterator/requirements/constexpr.cc
@@ -0,0 +1,24 @@
+// Copyright (C) 2019-2021 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 <iterator>
+
+constexpr std::ostream_iterator<int> iter1;
+constexpr std::ostream_iterator<int> iter2{};
diff --git a/libstdc++-v3/testsuite/std/ranges/97600.cc
b/libstdc++-v3/testsuite/std/ranges/97600.cc
index c642b9d22d0..7435de022cd 100644
--- a/libstdc++-v3/testsuite/std/ranges/97600.cc
+++ b/libstdc++-v3/testsuite/std/ranges/97600.cc
@@ -24,8 +24,9 @@
#include <ranges>
void
-test01(std::ranges::basic_istream_view<int, char, std::char_traits<char>> v)
+test01()
{
+ std::ranges::basic_istream_view<int, char, std::char_traits<char>> v;
v.begin();
static_assert(std::ranges::range<decltype(v)>);
}
diff --git a/libstdc++-v3/testsuite/std/ranges/p2325.cc
b/libstdc++-v3/testsuite/std/ranges/p2325.cc
index df6cde29e4d..72ba5c4a35d 100644
--- a/libstdc++-v3/testsuite/std/ranges/p2325.cc
+++ b/libstdc++-v3/testsuite/std/ranges/p2325.cc
@@ -2,6 +2,12 @@
// { dg-do compile { target c++20 } }
// P2325R3 "Views should not be required to be default constructible"
+// Parts of P2325R3 are deliberately omitted in libstdc++ 11, in particular the
+// removal of default ctors for back_/front_insert_iterator, ostream_iterator,
+// ref_view and basic_istream_view/::iterator, so as to maximize backward
+// compatibility with pre-P2325R3 code. So most static_asserts in this test
fail,
+// see the xfails at the end of this file.
+
#include <ranges>
#include <iterator>
#include <span>
@@ -153,3 +159,22 @@ test11()
using type2 = ranges::elements_view<ranges::single_view<pair<int,int>>, 0>;
static_assert(default_initializable<type2>);
}
+
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 35 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 36 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 37 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 38 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 43 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 47 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 57 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 58 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 63 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 67 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 76 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 84 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 124 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 126 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 128 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 138 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 148 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 158 }
