[v3 PATCH] Avoid endless run-time recursion for copying single-element tuples where the element type is by-value constructible from any type
Ville Voutilainen
ville.voutilainen@gmail.com
Sun May 8 11:44:00 GMT 2016
Tested on Linux-PPC64.
2016-05-08 Ville Voutilainen <ville.voutilainen@gmail.com>
Avoid endless run-time recursion for copying single-element
tuples where the element type is by-value constructible
from any type.
* include/std/tuple (_TC<>::_NotSameTuple): New.
* include/std/tuple (tuple(_UElements&&...): Use it.
* testsuite/20_util/tuple/cons/element_accepts_anything_byval.cc: New.
-------------- next part --------------
diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 53f3184..7522e43 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -500,6 +500,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__not_<is_constructible<_Elements..., _SrcTuple>>
>::value;
}
+ template<typename... _UElements>
+ static constexpr bool _NotSameTuple()
+ {
+ return __not_<is_same<tuple<_Elements...>,
+ typename remove_const<
+ typename remove_reference<_UElements...>::type
+ >::type>>::value;
+ }
};
template<typename... _Elements>
@@ -534,6 +542,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
return true;
}
+ template<typename... _UElements>
+ static constexpr bool _NotSameTuple()
+ {
+ return true;
+ }
};
/// Primary class template, tuple
@@ -611,7 +624,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Elements...>;
template<typename... _UElements, typename
- enable_if<_TMC<_UElements...>::template
+ enable_if<
+ _TC<sizeof...(_UElements) == 1, _Elements...>::template
+ _NotSameTuple<_UElements...>()
+ && _TMC<_UElements...>::template
_MoveConstructibleTuple<_UElements...>()
&& _TMC<_UElements...>::template
_ImplicitlyMoveConvertibleTuple<_UElements...>()
@@ -621,7 +637,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: _Inherited(std::forward<_UElements>(__elements)...) { }
template<typename... _UElements, typename
- enable_if<_TMC<_UElements...>::template
+ enable_if<
+ _TC<sizeof...(_UElements) == 1, _Elements...>::template
+ _NotSameTuple<_UElements...>()
+ && _TMC<_UElements...>::template
_MoveConstructibleTuple<_UElements...>()
&& !_TMC<_UElements...>::template
_ImplicitlyMoveConvertibleTuple<_UElements...>()
diff --git a/libstdc++-v3/testsuite/20_util/tuple/cons/element_accepts_anything_byval.cc b/libstdc++-v3/testsuite/20_util/tuple/cons/element_accepts_anything_byval.cc
new file mode 100644
index 0000000..fe9bea6
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/tuple/cons/element_accepts_anything_byval.cc
@@ -0,0 +1,30 @@
+// Copyright (C) 2016 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/>.
+
+#include <tuple>
+using namespace std;
+
+struct Something {
+ Something() { }
+ template <typename T> Something(T) { }
+};
+
+int main() {
+ tuple<Something> t1;
+ tuple<Something> t2 = t1;
+}
+
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