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libstdc++: LWG 3286 ranges::size is not required to be valid after ...

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... a call to ranges::begin on an input range.

This implements LWG 3286.  The new wording for the single-argument constructor
for subrange is implemented by splitting the constructor into two delegating
constructors, one constrained by _S_store_size and the other by !_S_store_size.

Tested on x86_64-pc-linux-gnu, both added tests fail before the patch and pass
with the patch.

libstdc++-v3/ChangeLog:

	LWG 3286 ranges::size is not required to be valid after a call to
	ranges::begin on an input range
	* include/std/ranges (subrange::subrange): Split single-argument
	constructor into two, one constrained by _S_store_size and another by
	!_S_store_size.
	(take_view::begin): Call size() before calling ranges::begin(_M_base).
	* testsuite/std/ranges/adaptors/lwg3286.cc: New test.
	* testsuite/std/ranges/subrange/lwg3286.cc: New test.
This commit is contained in:
Patrick Palka 2020-03-09 12:10:16 -04:00
parent 5115542a5c
commit 8f0d8cd852
4 changed files with 173 additions and 7 deletions
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11
libstdc++-v3/ChangeLog
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@ -1,3 +1,14 @@
2020-03-11 Patrick Palka <ppalka@redhat.com>
LWG 3286 ranges::size is not required to be valid after a call to
ranges::begin on an input range
* include/std/ranges (subrange::subrange): Split single-argument
constructor into two, one constrained by _S_store_size and another by
!_S_store_size.
(take_view::begin): Call size() before calling ranges::begin(_M_base).
* testsuite/std/ranges/adaptors/lwg3286.cc: New test.
* testsuite/std/ranges/subrange/lwg3286.cc: New test.
2020-03-10 Jonathan Wakely <jwakely@redhat.com>
* include/std/ranges (split_view::_OuterIter::__at_end): Use __current

26
libstdc++-v3/include/std/ranges
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@ -281,12 +281,18 @@ namespace ranges
&& __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>)
subrange(_Rng&& __r) requires _S_store_size && sized_range<_Rng>
: subrange{__r, ranges::size(__r)}
{ }
template<__detail::__not_same_as<subrange> _Rng>
requires borrowed_range<_Rng>
&& __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
&& convertible_to<sentinel_t<_Rng>, _Sent>
constexpr
subrange(_Rng&& __r) requires (!_S_store_size)
: subrange{ranges::begin(__r), ranges::end(__r)}
{
if constexpr (_S_store_size)
_M_size._M_size = ranges::size(__r);
}
{ }
template<borrowed_range _Rng>
requires __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
@ -2032,7 +2038,10 @@ namespace views
if constexpr (random_access_range<_Vp>)
return ranges::begin(_M_base);
else
return counted_iterator{ranges::begin(_M_base), size()};
{
auto __sz = size();
return counted_iterator{ranges::begin(_M_base), __sz};
}
}
else
return counted_iterator{ranges::begin(_M_base), _M_count};
@ -2046,7 +2055,10 @@ namespace views
if constexpr (random_access_range<const _Vp>)
return ranges::begin(_M_base);
else
return counted_iterator{ranges::begin(_M_base), size()};
{
auto __sz = size();
return counted_iterator{ranges::begin(_M_base), __sz};
}
}
else
return counted_iterator{ranges::begin(_M_base), _M_count};

72
libstdc++-v3/testsuite/std/ranges/adaptors/lwg3286.cc Normal file
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@ -0,0 +1,72 @@
// 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 run { target c++2a } }
#include <ranges>
#include <testsuite_iterators.h>
#include <testsuite_hooks.h>
using __gnu_test::test_input_range;
namespace ranges = std::ranges;
namespace views = std::views;
struct my_range
{
static inline int x[] = {1,2,3};
static inline test_input_range<int> r{x};
bool called_begin = false;
auto
begin()
{
called_begin = true;
return r.begin();
}
auto
end()
{
return r.end();
}
ranges::range_difference_t<decltype(r)>
size()
{
VERIFY( !called_begin );
return 3;
}
};
void
test01()
{
my_range r;
static_assert(!ranges::forward_range<my_range>);
static_assert(ranges::sized_range<my_range>);
auto v = r | views::take(3);
auto i = ranges::begin(v);
}
int
main()
{
test01();
}

71
libstdc++-v3/testsuite/std/ranges/subrange/lwg3286.cc Normal file
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@ -0,0 +1,71 @@
// 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 run { target c++2a } }
#include <ranges>
#include <testsuite_iterators.h>
#include <testsuite_hooks.h>
using __gnu_test::test_input_range;
namespace ranges = std::ranges;
struct my_range
{
static inline int x[] = {1,2,3};
static inline test_input_range<int> r{x};
bool called_begin = false;
auto
begin()
{
called_begin = true;
return r.begin();
}
auto
end()
{
return r.end();
}
ranges::range_difference_t<decltype(r)>
size()
{
VERIFY( !called_begin );
return 3;
}
};
void
test01()
{
my_range r;
static_assert(!ranges::forward_range<my_range>);
static_assert(ranges::sized_range<my_range>);
ranges::subrange sr = r;
VERIFY( ranges::size(sr) == 3 );
}
int
main()
{
test01();
}