Fix libstdc++/53841

[Jonathan Wakely]

        PR libstdc++/53841
        * include/std/condition_variable (condition_variable::wait_until):
        Handle clocks with higher resolution than __clock_t.
        (condition_variable::__wait_until_impl): Remove unnecessary _Clock
        parameter.
        * testsuite/30_threads/condition_variable/members/53841.cc: New.

Tested x86_64-linux, committed to trunk, 4.7 to follow shortly.
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commit ca23fd9a2b890d0f4e6a197dfb030b811c795f8a
Author: Jonathan Wakely <jwakely.gcc@gmail.com>
Date:   Thu Nov 15 01:21:46 2012 +0000

    	PR libstdc++/53841
    	* include/std/condition_variable (condition_variable::wait_until):
    	Handle clocks with higher resolution than __clock_t.
    	(condition_variable::__wait_until_impl): Remove unnecessary _Clock
    	parameter.
    	* testsuite/30_threads/condition_variable/members/53841.cc: New.

diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index a58d7f5..7d3d622 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -1,6 +1,6 @@
 // <condition_variable> -*- C++ -*-
 
-// Copyright (C) 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
+// Copyright (C) 2008-2012 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
@@ -107,8 +107,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	// DR 887 - Sync unknown clock to known clock.
 	const typename _Clock::time_point __c_entry = _Clock::now();
 	const __clock_t::time_point __s_entry = __clock_t::now();
-	const chrono::nanoseconds __delta = __atime - __c_entry;
-	const __clock_t::time_point __s_atime = __s_entry + __delta;
+	const auto __delta = __atime - __c_entry;
+	const auto __s_atime = __s_entry + __delta;
 
 	return __wait_until_impl(__lock, __s_atime);
       }
@@ -143,16 +143,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return &_M_cond; }
 
   private:
-    template<typename _Clock, typename _Duration>
+    template<typename _Dur>
       cv_status
       __wait_until_impl(unique_lock<mutex>& __lock,
-			const chrono::time_point<_Clock, _Duration>& __atime)
+			const chrono::time_point<__clock_t, _Dur>& __atime)
       {
-	chrono::time_point<__clock_t, chrono::seconds> __s =
-	  chrono::time_point_cast<chrono::seconds>(__atime);
-
-	chrono::nanoseconds __ns =
-	  chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
+	auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
+	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
 
 	__gthread_time_t __ts =
 	  {
@@ -163,7 +160,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	__gthread_cond_timedwait(&_M_cond, __lock.mutex()->native_handle(),
 				 &__ts);
 
-	return (_Clock::now() < __atime
+	return (__clock_t::now() < __atime
 		? cv_status::no_timeout : cv_status::timeout);
       }
   };
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/members/53841.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/members/53841.cc
new file mode 100644
index 0000000..62e44a6
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/members/53841.cc
@@ -0,0 +1,50 @@
+// { dg-do compile }
+// { dg-options " -std=gnu++0x -pthread" { target *-*-freebsd* *-*-netbsd* *-*-linux* powerpc-ibm-aix* } }
+// { dg-options " -std=gnu++0x -pthreads" { target *-*-solaris* } }
+// { dg-options " -std=gnu++0x " { target *-*-cygwin *-*-darwin* } }
+// { dg-require-cstdint "" }
+// { dg-require-gthreads "" }
+
+// Copyright (C) 2012 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/>.
+
+// PR libstdc++/53841
+
+#include <chrono>
+#include <mutex>
+#include <condition_variable>
+
+namespace ch = std::chrono;
+
+struct FPClock : ch::system_clock
+{
+    typedef double rep;
+    typedef std::ratio<1> period;
+    typedef ch::duration<rep, period> duration;
+    typedef ch::time_point<FPClock> time_point;
+
+    static time_point now()
+    { return time_point(duration(system_clock::now().time_since_epoch())); }
+};
+
+void f()
+{
+    std::mutex mx;
+    std::unique_lock<std::mutex> l(mx);
+    std::condition_variable cv;
+    cv.wait_until(l, FPClock::now());
+}