From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 8 Aug 2018 15:40:41 +0000 (+0100)
Subject: PR libstdc++/68519 use native duration to avoid rounding errors
X-Git-Tag: releases/gcc-6.5.0~122
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62ea33bbef023e14cace6c54487741b249429ed8;p=thirdparty%2Fgcc.git

PR libstdc++/68519 use native duration to avoid rounding errors

Backport from mainline
2017-12-14  Jonathan Wakely  <jwakely@redhat.com>

	PR libstdc++/68519
	* include/std/condition_variable (condition_variable::wait_for):
	Convert duration to native clock's duration before addition.
	* testsuite/30_threads/condition_variable/members/68519.cc: New test.

From-SVN: r263420
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index b278cc5ecc0e..9740f022408c 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,13 @@
 2018-08-08  Jonathan Wakely  <jwakely@redhat.com>
 
+	Backport from mainline
+	2017-12-14  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/68519
+	* include/std/condition_variable (condition_variable::wait_for):
+	Convert duration to native clock's duration before addition.
+	* testsuite/30_threads/condition_variable/members/68519.cc: New test.
+
 	Backport from mainline
 	2018-06-25  Jonathan Wakely  <jwakely@redhat.com>
 
diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index 62a7ee145196..8b3b6bc7aaaa 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -135,14 +135,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       cv_status
       wait_for(unique_lock<mutex>& __lock,
 	       const chrono::duration<_Rep, _Period>& __rtime)
-      { return wait_until(__lock, __clock_t::now() + __rtime); }
+      {
+	using __dur = typename __clock_t::duration;
+	auto __reltime = chrono::duration_cast<__dur>(__rtime);
+	if (__reltime < __rtime)
+	  ++__reltime;
+	return wait_until(__lock, __clock_t::now() + __reltime);
+      }
 
     template<typename _Rep, typename _Period, typename _Predicate>
       bool
       wait_for(unique_lock<mutex>& __lock,
 	       const chrono::duration<_Rep, _Period>& __rtime,
 	       _Predicate __p)
-      { return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
+      {
+	using __dur = typename __clock_t::duration;
+	auto __reltime = chrono::duration_cast<__dur>(__rtime);
+	if (__reltime < __rtime)
+	  ++__reltime;
+	return wait_until(__lock, __clock_t::now() + __reltime, std::move(__p));
+      }
 
     native_handle_type
     native_handle()
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/members/68519.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/members/68519.cc
new file mode 100644
index 000000000000..71c1d29e2312
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/members/68519.cc
@@ -0,0 +1,51 @@
+// 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 run }
+// { dg-options "-pthread"  }
+// { dg-require-effective-target c++11 }
+// { dg-require-effective-target pthread }
+// { dg-require-cstdint "" }
+// { dg-require-gthreads "" }
+
+#include <condition_variable>
+#include <testsuite_hooks.h>
+
+// PR libstdc++/68519
+
+bool val = false;
+std::mutex mx;
+std::condition_variable cv;
+
+void
+test01()
+{
+  for (int i = 0; i < 3; ++i)
+  {
+    std::unique_lock<std::mutex> l(mx);
+    auto start = std::chrono::system_clock::now();
+    cv.wait_for(l, std::chrono::duration<float>(1), [] { return val; });
+    auto t = std::chrono::system_clock::now();
+    VERIFY( (t - start) >= std::chrono::seconds(1) );
+  }
+}
+
+int
+main()
+{
+  test01();
+}