[gcc/devel/ranger] libstdc++: subrange converting constructor should disallow slicing (LWG 3282)
Aldy Hernandez
aldyh@gcc.gnu.org
Wed Jun 17 19:02:06 GMT 2020
https://gcc.gnu.org/g:77f5310f0205714538668b88fbf1de44f1f435be
commit 77f5310f0205714538668b88fbf1de44f1f435be
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Wed Feb 19 17:04:07 2020 +0000
libstdc++: subrange converting constructor should disallow slicing (LWG 3282)
* include/std/ranges (__detail::__convertible_to_non_slicing): New
helper concept.
(__detail::__pair_like_convertible_to): Remove.
(__detail::__pair_like_convertible_from): Add requirements for
non-slicing conversions.
(subrange): Constrain constructors with __convertible_to_non_slicing.
Remove constructors from pair-like types. Add new deduction guide.
* testsuite/std/ranges/subrange/lwg3282_neg.cc: New test.
Diff:
---
libstdc++-v3/ChangeLog | 9 ++++
libstdc++-v3/include/std/ranges | 48 ++++++++--------------
.../testsuite/std/ranges/subrange/lwg3282_neg.cc | 31 ++++++++++++++
3 files changed, 57 insertions(+), 31 deletions(-)
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 689bee8c2a9..6e22536680f 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,14 @@
2020-02-19 Jonathan Wakely <jwakely@redhat.com>
+ * include/std/ranges (__detail::__convertible_to_non_slicing): New
+ helper concept.
+ (__detail::__pair_like_convertible_to): Remove.
+ (__detail::__pair_like_convertible_from): Add requirements for
+ non-slicing conversions.
+ (subrange): Constrain constructors with __convertible_to_non_slicing.
+ Remove constructors from pair-like types. Add new deduction guide.
+ * testsuite/std/ranges/subrange/lwg3282_neg.cc: New test.
+
* include/bits/iterator_concepts.h (iter_move): Add declaration to
prevent unqualified lookup finding a suitable declaration (LWG 3247).
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index b0806750a08..b348ba2cfcb 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -214,6 +214,12 @@ namespace ranges
namespace __detail
{
+ template<class _From, class _To>
+ concept __convertible_to_non_slicing = convertible_to<_From, _To>
+ && !(is_pointer_v<decay_t<_From>> && is_pointer_v<decay_t<_To>>
+ && __not_same_as<remove_pointer_t<decay_t<_From>>,
+ remove_pointer_t<decay_t<_To>>>);
+
template<typename _Tp>
concept __pair_like
= !is_reference_v<_Tp> && requires(_Tp __t)
@@ -226,19 +232,12 @@ namespace ranges
{ get<1>(__t) } -> convertible_to<const tuple_element_t<1, _Tp>&>;
};
- template<typename _Tp, typename _Up, typename _Vp>
- concept __pair_like_convertible_to
- = !range<_Tp> && __pair_like<remove_reference_t<_Tp>>
- && requires(_Tp&& __t)
- {
- { get<0>(std::forward<_Tp>(__t)) } -> convertible_to<_Up>;
- { get<1>(std::forward<_Tp>(__t)) } -> convertible_to<_Vp>;
- };
-
template<typename _Tp, typename _Up, typename _Vp>
concept __pair_like_convertible_from
= !range<_Tp> && __pair_like<_Tp>
- && constructible_from<_Tp, _Up, _Vp>;
+ && constructible_from<_Tp, _Up, _Vp>
+ && __convertible_to_non_slicing<_Up, tuple_element_t<0, _Tp>>
+ && convertible_to<_Vp, tuple_element_t<1, _Tp>>;
template<typename _Tp>
concept __iterator_sentinel_pair
@@ -277,12 +276,13 @@ namespace ranges
subrange() = default;
constexpr
- subrange(_It __i, _Sent __s) requires (!_S_store_size)
+ subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s)
+ requires (!_S_store_size)
: _M_begin(std::move(__i)), _M_end(__s)
{ }
constexpr
- subrange(_It __i, _Sent __s,
+ subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s,
__detail::__make_unsigned_like_t<iter_difference_t<_It>> __n)
requires (_Kind == subrange_kind::sized)
: _M_begin(std::move(__i)), _M_end(__s)
@@ -295,7 +295,7 @@ namespace ranges
template<__detail::__not_same_as<subrange> _Rng>
requires borrowed_range<_Rng>
- && convertible_to<iterator_t<_Rng>, _It>
+ && __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
&& convertible_to<sentinel_t<_Rng>, _Sent>
constexpr
subrange(_Rng&& __r) requires (!_S_store_size || sized_range<_Rng>)
@@ -306,7 +306,7 @@ namespace ranges
}
template<borrowed_range _Rng>
- requires convertible_to<iterator_t<_Rng>, _It>
+ requires __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
&& convertible_to<sentinel_t<_Rng>, _Sent>
constexpr
subrange(_Rng&& __r,
@@ -315,23 +315,6 @@ namespace ranges
: subrange{ranges::begin(__r), ranges::end(__r), __n}
{ }
- template<__detail::__not_same_as<subrange> _PairLike>
- requires __detail::__pair_like_convertible_to<_PairLike, _It, _Sent>
- constexpr
- subrange(_PairLike&& __r) requires (!_S_store_size)
- : subrange{std::get<0>(std::forward<_PairLike>(__r)),
- std::get<1>(std::forward<_PairLike>(__r))}
- { }
-
- template<__detail::__pair_like_convertible_to<_It, _Sent> _PairLike>
- constexpr
- subrange(_PairLike&& __r,
- __detail::__make_unsigned_like_t<iter_difference_t<_It>> __n)
- requires (_Kind == subrange_kind::sized)
- : subrange{std::get<0>(std::forward<_PairLike>(__r)),
- std::get<1>(std::forward<_PairLike>(__r)), __n}
- { }
-
template<__detail::__not_same_as<subrange> _PairLike>
requires __detail::__pair_like_convertible_from<_PairLike, const _It&,
const _Sent&>
@@ -402,6 +385,9 @@ namespace ranges
}
};
+ template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
+ subrange(_It, _Sent) -> subrange<_It, _Sent>;
+
template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
subrange(_It, _Sent,
__detail::__make_unsigned_like_t<iter_difference_t<_It>>)
diff --git a/libstdc++-v3/testsuite/std/ranges/subrange/lwg3282_neg.cc b/libstdc++-v3/testsuite/std/ranges/subrange/lwg3282_neg.cc
new file mode 100644
index 00000000000..5c2f1de45ad
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/subrange/lwg3282_neg.cc
@@ -0,0 +1,31 @@
+// 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 <ranges>
+
+using std::ranges::subrange;
+
+// LWG 3282. subrange converting constructor should disallow derived to base
+// conversions
+
+struct Base {};
+struct Derived : Base {};
+subrange<Derived*> sd;
+subrange<Base*> sb = sd; // { dg-error "conversion" }
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