@@ -754,15 +754,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Destructible and constructible type properties.
- template<typename>
- struct add_rvalue_reference;
-
/**
* @brief Utility to simplify expressions used in unevaluated operands
* @ingroup utilities
*/
+
+ template<typename _Tp, typename _Up = _Tp&&>
+ _Up
+ __declval(int);
+
template<typename _Tp>
- typename add_rvalue_reference<_Tp>::type declval() noexcept;
+ _Tp
+ __declval(long);
+
+ template<typename _Tp>
+ auto declval() noexcept -> decltype(__declval<_Tp>(0));
template<typename, unsigned = 0>
struct extent;
@@ -2079,16 +2085,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct __declval_protector
{
static const bool __stop = false;
- static typename add_rvalue_reference<_Tp>::type __delegate();
};
template<typename _Tp>
- inline typename add_rvalue_reference<_Tp>::type
- declval() noexcept
+ auto declval() noexcept -> decltype(__declval<_Tp>(0))
{
static_assert(__declval_protector<_Tp>::__stop,
"declval() must not be used!");
- return __declval_protector<_Tp>::__delegate();
+ return __declval<_Tp>(0);
}
/// result_of
@@ -18,7 +18,7 @@
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
-// { dg-error "static assertion failed" "" { target *-*-* } 2089 }
+// { dg-error "static assertion failed" "" { target *-*-* } 2093 }
#include <utility>
@@ -47,4 +47,4 @@ void test01()
// { dg-error "required from here" "" { target *-*-* } 39 }
// { dg-error "required from here" "" { target *-*-* } 41 }
-// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1754 }
+// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1760 }
@@ -47,5 +47,5 @@ void test01()
// { dg-error "required from here" "" { target *-*-* } 39 }
// { dg-error "required from here" "" { target *-*-* } 41 }
-// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1650 }
+// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1656 }
This implements Eric Niebler's suggestion of a more lightweight std::declval, which doesn't need to instantiate std::add_rvalue_reference (and its base class and helpers). PR libstdc++/71187 * include/std/type_traits (__declval): New function to deduce return type of declval. (__declval_protector::_delegate): Remove. (declval): Use __declval instead of add_rvalue_reference and __declval_protector::__delegate. * testsuite/20_util/declval/requirements/1_neg.cc: Adjust dg-error lineno. * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Likewise. * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: Likewise. Tested powerpc64le-linux, committed to trunk. commit 05558f97c64247cf421eff8b17570a0844794cbc Author: Jonathan Wakely <jwakely@redhat.com> Date: Fri Sep 15 14:49:08 2017 +0100 PR libstdc++/71187 reimplement declval without add_rvalue_reference PR libstdc++/71187 * include/std/type_traits (__declval): New function to deduce return type of declval. (__declval_protector::_delegate): Remove. (declval): Use __declval instead of add_rvalue_reference and __declval_protector::__delegate. * testsuite/20_util/declval/requirements/1_neg.cc: Adjust dg-error lineno. * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Likewise. * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: Likewise.