chrono (duration<>::duration(const duration<>&)): Fix per the straightforward resolution of DR 974.

2009-10-26  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/std/chrono (duration<>::duration(const duration<>&)): Fix
	per the straightforward resolution of DR 974.
	* testsuite/20_util/duration/cons/dr974.cc: Add.

From-SVN: r153581

libstdc++-v3/ChangeLog

+2009-10-26  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	* include/std/chrono (duration<>::duration(const duration<>&)): Fix
+	per the straightforward resolution of DR 974.
+	* testsuite/20_util/duration/cons/dr974.cc: Add.
+
 2009-10-26  Jakub Jelinek  <jakub@redhat.com>
 
 	PR libstdc++/38923

libstdc++-v3/include/std/chrono

@@ -225,7 +225,8 @@ namespace std
           : __r(duration_cast<duration>(__d).count())
           {
             static_assert(treat_as_floating_point<rep>::value == true 
-              || ratio_divide<_Period2, period>::type::den == 1, 
+			  || (ratio_divide<_Period2, period>::type::den == 1
+			      && !treat_as_floating_point<_Rep2>::value), 
               "the resulting duration is not exactly representable");
           }
 

libstdc++-v3/testsuite/20_util/duration/cons/dr974.cc

+// { dg-do compile }
+// { dg-options "-std=gnu++0x" }
+// { dg-require-cstdint "" }
+
+// Copyright (C) 2009 Free Software Foundation
+//
+// 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/>.
+
+// 20.8.3.1 duration constructors [time.duration.cons]
+
+#include <chrono>
+
+// DR 974.
+void test01()
+{
+  using namespace std::chrono;
+
+  duration<double> d(3.5);
+  duration<int> i = d;  // implicit truncation, should not compile
+}
+
+// { dg-error "instantiated from here" "" { target *-*-* } 32 }
+// { dg-error "not exactly representable" "" { target *-*-* } 227 }
+// { dg-excess-errors "In instantiation of" }