[committed] libstdc++: Fix view adaptors for mixed-const sentinels and iterators (PR 95322)
Jonathan Wakely
jwakely@redhat.com
Wed May 27 21:09:21 GMT 2020
The bug report is that transform_view's sentinel<false> cannot be
compared to its iterator<true>. The comparison is supposed to use
operator==(iterator<Const>, sentinel<Const>) after converting
sentinel<false> to sentinel<true>. However, the operator== is a hidden
friend so is not a candidate when comparing iterator<true> with
sentinel<false>. The required conversion would only happen if we'd found
the operator, but we can't find the operator until after the conversion
happens.
A new LWG issue has been reported, but not yet assigned a number. The
solution suggested by Casey Carter is to make the hidden friends of the
sentinel types work with iterators of any const-ness, so that no
conversions are required.
Patrick Palka observed that join_view has a similar problem and a
similar fix is used for its sentinel.
PR libstdc++/95322
* include/std/ranges (transform_view::_Sentinel): Allow hidden
friends to work with _Iterator<true> and _Iterator<false>.
(join_view::_Sentinel): Likewise.
* testsuite/std/ranges/adaptors/95322.cc: New test.
Tested powerpc64le-linux, committed to master.
I intend to backport this to gcc-10 as well.
-------------- next part --------------
commit 6c2582c0406250c66e2eb3651f8e8638796b7f53
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Wed May 27 22:08:15 2020 +0100
libstdc++: Fix view adaptors for mixed-const sentinels and iterators (PR 95322)
The bug report is that transform_view's sentinel<false> cannot be
compared to its iterator<true>. The comparison is supposed to use
operator==(iterator<Const>, sentinel<Const>) after converting
sentinel<false> to sentinel<true>. However, the operator== is a hidden
friend so is not a candidate when comparing iterator<true> with
sentinel<false>. The required conversion would only happen if we'd found
the operator, but we can't find the operator until after the conversion
happens.
A new LWG issue has been reported, but not yet assigned a number. The
solution suggested by Casey Carter is to make the hidden friends of the
sentinel types work with iterators of any const-ness, so that no
conversions are required.
Patrick Palka observed that join_view has a similar problem and a
similar fix is used for its sentinel.
PR libstdc++/95322
* include/std/ranges (transform_view::_Sentinel): Allow hidden
friends to work with _Iterator<true> and _Iterator<false>.
(join_view::_Sentinel): Likewise.
* testsuite/std/ranges/adaptors/95322.cc: New test.
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 0c602c7200f..b8023e67c9f 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1853,7 +1853,7 @@ namespace views
{ return ranges::iter_swap(__x._M_current, __y._M_current); }
friend _Iterator<!_Const>;
- friend _Sentinel<_Const>;
+ template<bool> friend struct _Sentinel;
};
template<bool _Const>
@@ -1863,13 +1863,15 @@ namespace views
using _Parent = __detail::__maybe_const_t<_Const, transform_view>;
using _Base = __detail::__maybe_const_t<_Const, _Vp>;
- constexpr range_difference_t<_Base>
- __distance_from(const _Iterator<_Const>& __i) const
- { return _M_end - __i._M_current; }
+ template<bool _Const2>
+ constexpr range_difference_t<_Base>
+ __distance_from(const _Iterator<_Const2>& __i) const
+ { return _M_end - __i._M_current; }
- constexpr bool
- __equal(const _Iterator<_Const>& __i) const
- { return __i._M_current == _M_end; }
+ template<bool _Const2>
+ constexpr bool
+ __equal(const _Iterator<_Const2>& __i) const
+ { return __i._M_current == _M_end; }
sentinel_t<_Base> _M_end = sentinel_t<_Base>();
@@ -1892,19 +1894,26 @@ namespace views
base() const
{ return _M_end; }
- friend constexpr bool
- operator==(const _Iterator<_Const>& __x, const _Sentinel& __y)
- { return __y.__equal(__x); }
+ template<bool _Const2>
+ requires sentinel_for<sentinel_t<_Base>,
+ iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
+ friend constexpr bool
+ operator==(const _Iterator<_Const2>& __x, const _Sentinel& __y)
+ { return __y.__equal(__x); }
- friend constexpr range_difference_t<_Base>
- operator-(const _Iterator<_Const>& __x, const _Sentinel& __y)
- requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
- { return -__y.__distance_from(__x); }
+ template<bool _Const2>
+ requires sized_sentinel_for<sentinel_t<_Base>,
+ iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
+ friend constexpr range_difference_t<_Base>
+ operator-(const _Iterator<_Const2>& __x, const _Sentinel& __y)
+ { return -__y.__distance_from(__x); }
- friend constexpr range_difference_t<_Base>
- operator-(const _Sentinel& __y, const _Iterator<_Const>& __x)
- requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
- { return __y.__distance_from(__x); }
+ template<bool _Const2>
+ requires sized_sentinel_for<sentinel_t<_Base>,
+ iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
+ friend constexpr range_difference_t<_Base>
+ operator-(const _Sentinel& __y, const _Iterator<_Const2>& __x)
+ { return __y.__distance_from(__x); }
friend _Sentinel<!_Const>;
};
@@ -2571,7 +2580,7 @@ namespace views
{ return ranges::iter_swap(__x._M_inner, __y._M_inner); }
friend _Iterator<!_Const>;
- friend _Sentinel<_Const>;
+ template<bool> friend struct _Sentinel;
};
template<bool _Const>
@@ -2581,9 +2590,10 @@ namespace views
using _Parent = __detail::__maybe_const_t<_Const, join_view>;
using _Base = __detail::__maybe_const_t<_Const, _Vp>;
- constexpr bool
- __equal(const _Iterator<_Const>& __i) const
- { return __i._M_outer == _M_end; }
+ template<bool _Const2>
+ constexpr bool
+ __equal(const _Iterator<_Const2>& __i) const
+ { return __i._M_outer == _M_end; }
sentinel_t<_Base> _M_end = sentinel_t<_Base>();
@@ -2601,9 +2611,12 @@ namespace views
: _M_end(std::move(__s._M_end))
{ }
- friend constexpr bool
- operator==(const _Iterator<_Const>& __x, const _Sentinel& __y)
- { return __y.__equal(__x); }
+ template<bool _Const2>
+ requires sentinel_for<sentinel_t<_Base>,
+ iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
+ friend constexpr bool
+ operator==(const _Iterator<_Const2>& __x, const _Sentinel& __y)
+ { return __y.__equal(__x); }
friend _Sentinel<!_Const>;
};
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/95322.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/95322.cc
index 44619d6719a..9279d5520a8 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/95322.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/95322.cc
@@ -15,36 +15,44 @@
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
-// { dg-options "-std=gnu++2a" }
+// { dg-options "-std=gnu++20" }
// { dg-do run { target c++2a } }
#include <ranges>
-#include <list>
-#include <testsuite_hooks.h>
+#include <testsuite_iterators.h>
-namespace ranges = std::ranges;
-namespace views = std::views;
+using __gnu_test::test_forward_range;
void
test01()
{
- std::list container{1, 2, 3, 4, 5};
- auto v = (container
- | views::take(3)
- | views::transform(std::negate{})
- | views::common);
- auto i = ranges::cbegin(v);
- VERIFY( *i == -1 );
- ++i;
- VERIFY( *i == -2 );
- ++i;
- VERIFY( *i == -3 );
- ++i;
- VERIFY( i == ranges::end(v) );
+ // PR libstdc++/95322
+ int a[2]{1, 2};
+ test_forward_range<int> v{a};
+ auto view1 = v | std::views::take(2);
+ auto view2 = view1 | std::views::transform(std::identity{});
+ const bool eq = std::ranges::cbegin(view2) == std::ranges::end(view2);
+ VERIFY( !eq );
}
-int
-main()
+void
+test02()
+{
+ using irange = test_forward_range<int>;
+
+ int a[2]{1, 2};
+ int b[3]{3, 4, 5};
+ irange u[2]{ irange{a}, irange{b} };
+ test_forward_range<irange> v{u};
+ auto view = (std::views::counted(v.begin(), 2)
+ | std::views::transform(std::identity{})
+ | std::views::join);
+ const bool eq = std::ranges::cbegin(view) == std::ranges::end(view);
+ VERIFY( !eq );
+}
+
+int main()
{
test01();
+ test02();
}
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