On 01/05/20 14:28 +0100, Jonathan Wakely wrote:
On 01/05/20 13:03 +0100, Jonathan Wakely wrote:
The deduced return type causes the instantiation of the function body,
which can then require the instantiation of std::projected::operator*
which is intentionally not defined.
This patch uses a helper trait to define the return type, so that the
function body doesn't need to be instantiated. That helper trait can
then also be used in other places that currently check the return type
of ranges::iter_move (iter_rvalue_reference_t and indirectly_readable).
2020-05-01 Jonathan Wakely <jwak...@redhat.com>
Patrick Palka <ppa...@redhat.com>
PR libstdc++/92894
* include/bits/iterator_concepts.h (ranges::__cust_imove::_IMove):
Add trait to determine return type and an alias for it.
(ranges::__cust_imove::_IMove::operator()): Use __result instead of
deduced return type.
(iter_rvalue_reference_t): Use _IMove::__type instead of checking
the result of ranges::iter_move.
(__detail::__indirectly_readable_impl): Use iter_rvalue_reference_t
instead of checking the result of ranges::iter_move.
* testsuite/24_iterators/indirect_callable/92894.cc: New test.
Patrick, I prefer this to the patch you added to the bug. Avoiding
doing overload resolution on ranges::iter_move(x) seems worthwhile.
What do you think?
I *think* the changes to __indirectly_readable_impl are equivalent. As
far as I can tell, the point of the original { *in }
and { ranges::iter_move(in) } constraints are to check that const In
and In do the same thing. We could leave the { *in } on, but for
consistency it seems better to change both.
Here's a slightly improved patch which I'm committing now.
Diffs from the previous patch are removing the useless parameter list
from the __indirectly_readable_impl concept:
@@ -460,7 +461,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __iter_concept = typename __iter_concept_impl<_Iter>::type;
template<typename _In>
- concept __indirectly_readable_impl = requires(const _In __in)
+ concept __indirectly_readable_impl = requires
{
typename iter_value_t<_In>;
typename iter_reference_t<_In>;
Fixing 24_iterators/indirect_callable/92894.cc so it actually passes,
and adding 24_iterators/customization_points/92894.cc to verify that
iter_move is fixed (which the other tests don't do because
indirectly_readable no longer uses ranges::iter_move).
This is the patch I'm testing for the gcc-10 branch (if it gets RM
approval). It doesn't do the compile-time optimization for
iter_rvalue_reference_t and __indirectly_readable_impl, it just fixes
the bug in ranges::iter_move. The optimization isn't required for
correctness.
commit 838d37183df0592ae1eb814bbf0461e17cf95e33
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri May 1 14:35:12 2020 +0100
libstdc++: Replace deduced return type in ranges::iter_move (PR 92894)
The deduced return type causes the instantiation of the function body,
which can then require the instantiation of std::projected::operator*
which is intentionally not defined.
This patch uses a helper trait to define the return type, so that the
function body doesn't need to be instantiated.
Unlike on the master branch, this backport to gcc-10 does not change the
iter_rvalue_reference_t alias template and __indirectly_readable_impl
concept to use the new trait.
Backport from mainline
2020-05-01 Jonathan Wakely <jwak...@redhat.com>
Patrick Palka <ppa...@redhat.com>
PR libstdc++/92894
* include/bits/iterator_concepts.h (ranges::__cust_imove::_IMove):
Add trait to determine return type and an alias for it.
(ranges::__cust_imove::_IMove::operator()): Use __result instead of
deduced return type.
* testsuite/24_iterators/customization_points/92894.cc: New test.
* testsuite/24_iterators/indirect_callable/92894.cc: New test.
diff --git a/libstdc++-v3/include/bits/iterator_concepts.h b/libstdc++-v3/include/bits/iterator_concepts.h
index b598532089e..c5b6247cde7 100644
--- a/libstdc++-v3/include/bits/iterator_concepts.h
+++ b/libstdc++-v3/include/bits/iterator_concepts.h
@@ -89,6 +89,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct _IMove
{
private:
+ template<typename _Tp>
+ struct __result
+ { using type = iter_reference_t<_Tp>; };
+
+ template<typename _Tp>
+ requires __adl_imove<_Tp>
+ struct __result<_Tp>
+ { using type = decltype(iter_move(std::declval<_Tp>())); };
+
+ template<typename _Tp>
+ requires (!__adl_imove<_Tp>)
+ && is_lvalue_reference_v<iter_reference_t<_Tp>>
+ struct __result<_Tp>
+ { using type = remove_reference_t<iter_reference_t<_Tp>>&&; };
+
template<typename _Tp>
static constexpr bool
_S_noexcept()
@@ -100,16 +115,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
public:
- template<typename _Tp>
- requires __adl_imove<_Tp> || requires(_Tp& __e) { *__e; }
- constexpr decltype(auto)
+ // The result type of iter_move(std::declval<_Tp>())
+ template<std::__detail::__dereferenceable _Tp>
+ using __type = typename __result<_Tp>::type;
+
+ template<std::__detail::__dereferenceable _Tp>
+ constexpr __type<_Tp>
operator()(_Tp&& __e) const
noexcept(_S_noexcept<_Tp>())
{
if constexpr (__adl_imove<_Tp>)
return iter_move(static_cast<_Tp&&>(__e));
- else if constexpr (is_reference_v<iter_reference_t<_Tp>>)
- return std::move(*__e);
+ else if constexpr (is_lvalue_reference_v<iter_reference_t<_Tp>>)
+ return static_cast<__type<_Tp>>(*__e);
else
return *__e;
}
diff --git a/libstdc++-v3/testsuite/24_iterators/customization_points/92894.cc b/libstdc++-v3/testsuite/24_iterators/customization_points/92894.cc
new file mode 100644
index 00000000000..197268fe5e3
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/customization_points/92894.cc
@@ -0,0 +1,52 @@
+// 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 <iterator>
+
+using namespace std;
+
+// Define our own of version of indirectly_readable_impl here,
+// to check the use of iter_move even if the real concept in
+// <bits/iterator_concepts.h> no longer uses iter_move.
+template<class In>
+concept indirectly_readable_impl
+ = requires(const In in)
+ {
+ typename iter_value_t<In>;
+ typename iter_reference_t<In>;
+ typename iter_rvalue_reference_t<In>;
+ { *in } -> same_as<iter_reference_t<In>>;
+ { ranges::iter_move(in) } -> same_as<iter_rvalue_reference_t<In>>;
+ };
+
+template<class T> requires indirectly_readable_impl<projected<T*, identity>>
+ void algo(T)
+ { }
+
+void
+test01()
+{
+ // PR libstdc++/92894
+ // Verify that the use of range::iter_move above doesn't cause odr-use of
+ // projected<local-class-type, identity>::operator* (which is not defined).
+ struct X { };
+ X a;
+ algo(a);
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/indirect_callable/92894.cc b/libstdc++-v3/testsuite/24_iterators/indirect_callable/92894.cc
new file mode 100644
index 00000000000..3408c76bde1
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/indirect_callable/92894.cc
@@ -0,0 +1,55 @@
+// 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 <iterator>
+
+using std::projected;
+using std::identity;
+using std::indirect_unary_predicate;
+
+template<typename T,
+ indirect_unary_predicate<projected<T*, identity>> Pred>
+ constexpr void
+ all_of(T*, Pred)
+ { }
+
+void
+test01()
+{
+ // PR libstdc++/92894
+ struct X { };
+ X x;
+ all_of(&x, [](X&) { return false; });
+}
+
+template<class R, class Proj = identity,
+ indirect_unary_predicate<projected<R, Proj>> Pred>
+ constexpr void
+ find_if(R, Pred, Proj = {})
+ { }
+
+void
+test02()
+{
+ // PR 94241
+ struct s { int m; };
+ s r[] = { s{0}, s{1}, s{2}, s{3} };
+ find_if(r, [](auto const) { return true; });
+}
