On 13/09/17 15:09 +0100, Jonathan Wakely wrote:
Howard reported this bug, caused by a missing SFINAE constraint on a
std::chrono::time_point constructor.
I've also done a bit of simplification using alias templates.
Here's the backport for the branches, which just adds the constraint
(and tests) without the new alias templates.
commit 4a6c846f3203dd0ceb13b7130e686833a4150d96
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Sep 13 15:16:31 2017 +0100
PR libstdc++/81468 constrain std::chrono::time_point constructor
PR libstdc++/81468
* include/std/chrono (time_point(const time_point<_Dur2>&)): Add
missing constraint from LWG DR 1177.
* testsuite/20_util/duration/cons/dr1177.cc: New.
* testsuite/20_util/time_point/cons/81468.cc: New.
* testsuite/20_util/duration/literals/range.cc: Update dg-error line.
diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index c3a6ba8f873..cc63d44657b 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -622,7 +622,8 @@ _GLIBCXX_END_NAMESPACE_VERSION
{ }
// conversions
- template<typename _Dur2>
+ template<typename _Dur2,
+ typename = _Require<is_convertible<_Dur2, _Dur>>>
constexpr time_point(const time_point<clock, _Dur2>& __t)
: __d(__t.time_since_epoch())
{ }
diff --git a/libstdc++-v3/testsuite/20_util/duration/cons/dr1177.cc b/libstdc++-v3/testsuite/20_util/duration/cons/dr1177.cc
new file mode 100644
index 00000000000..28c881ccc79
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/duration/cons/dr1177.cc
@@ -0,0 +1,41 @@
+// Copyright (C) 2017 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-do compile { target c++11 } }
+
+#include <chrono>
+#include <type_traits>
+
+using namespace std;
+using namespace std::chrono;
+
+// DR 1177
+static_assert(is_constructible<duration<float>, duration<double>>{},
+ "can convert duration with one floating point rep to another");
+static_assert(is_constructible<duration<float>, duration<int>>{},
+ "can convert duration with integral rep to one with floating point rep");
+static_assert(!is_constructible<duration<int>, duration<float>>{},
+ "cannot convert duration with floating point rep to one with integral rep");
+static_assert(is_constructible<duration<int>, duration<long>>{},
+ "can convert duration with one integral rep to another");
+
+static_assert(!is_constructible<duration<int>, duration<int, ratio<2,3>>>{},
+ "cannot convert duration to one with different period");
+static_assert(is_constructible<duration<float>, duration<int, ratio<2,3>>>{},
+ "unless it has a floating-point representation");
+static_assert(is_constructible<duration<float>, duration<int, ratio<1,3>>>{},
+ "or a period that is an integral multiple of the original");
diff --git a/libstdc++-v3/testsuite/20_util/duration/literals/range.cc b/libstdc++-v3/testsuite/20_util/duration/literals/range.cc
index c0d1a6e5885..531b53c42ec 100644
--- a/libstdc++-v3/testsuite/20_util/duration/literals/range.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/literals/range.cc
@@ -26,6 +26,6 @@ test01()
// std::numeric_limits<int64_t>::max() == 9223372036854775807;
auto h = 9223372036854775808h;
- // { dg-error "cannot be represented" "" { target *-*-* } 892 }
+ // { dg-error "cannot be represented" "" { target *-*-* } 893 }
}
// { dg-prune-output "in constexpr expansion" } // needed for -O0
diff --git a/libstdc++-v3/testsuite/20_util/time_point/cons/81468.cc b/libstdc++-v3/testsuite/20_util/time_point/cons/81468.cc
new file mode 100644
index 00000000000..30d1c4a5ac7
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/time_point/cons/81468.cc
@@ -0,0 +1,34 @@
+// Copyright (C) 2017 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-do compile { target c++11 } }
+
+#include <chrono>
+#include <type_traits>
+
+using namespace std;
+using namespace std::chrono;
+
+template <class Duration>
+ using sys_time = time_point<system_clock, Duration>;
+
+static_assert(is_constructible<sys_time<milliseconds>, sys_time<seconds>>{},
+ "Can construct time_point from one with lower precision duration");
+
+// PR libstdc++/81468 - DR 1177
+static_assert(!is_constructible<sys_time<seconds>, sys_time<milliseconds>>{},
+ "Cannot construct time_point from one with higher precision duration");
