diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index c97e46b96d9..91d2a598ee5 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,22 @@
+2009-10-31  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	* include/std/chrono (struct __common_rep_type): New.
+	(duration_cast(const duration<>&),
+	duration<>::duration(const _Rep2&),
+	duration<>::duration(const duration<>&),
+	operator*(const duration<>&, const _Rep2&),
+	operator*(const _Rep1&, const duration<>&),
+	operator/(const duration<>&, const _Rep2&),
+	time_point_cast(const time_point<>&)): Implement resolution of
+	DR 1177 ([Ready] in Santa Cruz), change to not participate to
+	overload resolution if the constraints are not met. 
+	* testsuite/20_util/duration/cons/1_neg.cc: Adjust dg-errors.
+	* testsuite/20_util/duration/cons/dr974.cc: Likewise.
+	* testsuite/20_util/duration/requirements/typedefs_neg1.cc: Adjust
+	dg-error line numbers.
+	* testsuite/20_util/duration/requirements/typedefs_neg2.cc: Likewise.
+	* testsuite/20_util/duration/requirements/typedefs_neg3.cc: Likewise.
+
 2009-10-31  Gerald Pfeifer  <gerald@pfeifer.com>
 
 	* doc/xml/manual/intro.xml: Refer to our bugs page instead of
diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index 300c13ce97e..e80ec13c093 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -138,9 +138,20 @@ namespace std
           }
       };
 
+    template<typename _Tp>
+      struct __is_duration
+      : std::false_type
+      { };
+
+    template<typename _Rep, typename _Period>
+      struct __is_duration<duration<_Rep, _Period>>
+      : std::true_type
+      { };
+
     /// duration_cast
     template<typename _ToDuration, typename _Rep, typename _Period>
-      inline _ToDuration
+      inline typename enable_if<__is_duration<_ToDuration>::value,
+				_ToDuration>::type
       duration_cast(const duration<_Rep, _Period>& __d)
       {
         typedef typename
@@ -175,16 +186,6 @@ namespace std
         { return numeric_limits<_Rep>::min(); }
       };
 
-    template<typename _Tp>
-      struct __is_duration
-      : std::false_type
-      { };
-
-    template<typename _Rep, typename _Period>
-      struct __is_duration<duration<_Rep, _Period>>
-      : std::true_type
-      { };
-
     template<typename T>
       struct __is_ratio
       : std::false_type
@@ -210,25 +211,19 @@ namespace std
         // 20.8.3.1 construction / copy / destroy
 	duration() = default;
 
-        template<typename _Rep2>
+        template<typename _Rep2, typename = typename
+	       enable_if<is_convertible<_Rep2, rep>::value
+			 && (treat_as_floating_point<rep>::value
+			     || !treat_as_floating_point<_Rep2>::value)>::type>
           explicit duration(const _Rep2& __rep)
-          : __r(static_cast<rep>(__rep))
-          {
-            static_assert(is_convertible<_Rep2,rep>::value 
-			  && (treat_as_floating_point<rep>::value 
-			      || !treat_as_floating_point<_Rep2>::value),
-	      "cannot construct integral duration with floating point type");
-          }
+          : __r(static_cast<rep>(__rep)) { }
 
-        template<typename _Rep2, typename _Period2>
+        template<typename _Rep2, typename _Period2, typename = typename
+	       enable_if<treat_as_floating_point<rep>::value 
+			 || (ratio_divide<_Period2, period>::type::den == 1
+			     && !treat_as_floating_point<_Rep2>::value)>::type>
           duration(const duration<_Rep2, _Period2>& __d)
-          : __r(duration_cast<duration>(__d).count())
-          {
-            static_assert(treat_as_floating_point<rep>::value == true 
-			  || (ratio_divide<_Period2, period>::type::den == 1
-			      && !treat_as_floating_point<_Rep2>::value), 
-              "the resulting duration is not exactly representable");
-          }
+          : __r(duration_cast<duration>(__d).count()) { }
 
 	~duration() = default;
 	duration(const duration&) = default;
@@ -359,8 +354,17 @@ namespace std
         return __ct(__lhs) -= __rhs;
       }
 
+    template<typename _Rep1, typename _Rep2, bool =
+	     is_convertible<_Rep2,
+			    typename common_type<_Rep1, _Rep2>::type>::value>
+      struct __common_rep_type { };
+
+    template<typename _Rep1, typename _Rep2>
+      struct __common_rep_type<_Rep1, _Rep2, true>
+      { typedef typename common_type<_Rep1, _Rep2>::type type; };     
+
     template<typename _Rep1, typename _Period, typename _Rep2>
-      inline duration<typename common_type<_Rep1, _Rep2>::type, _Period>
+      inline duration<typename __common_rep_type<_Rep1, _Rep2>::type, _Period>
       operator*(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
       {
         typedef typename common_type<_Rep1, _Rep2>::type __cr;
@@ -368,12 +372,12 @@ namespace std
       }
 
     template<typename _Rep1, typename _Period, typename _Rep2>
-      inline duration<typename common_type<_Rep1, _Rep2>::type, _Period>
-      operator*(const _Rep2& __s, const duration<_Rep1, _Period>& __d)
+      inline duration<typename __common_rep_type<_Rep2, _Rep1>::type, _Period>
+      operator*(const _Rep1& __s, const duration<_Rep2, _Period>& __d)
       { return __d * __s; }
  
     template<typename _Rep1, typename _Period, typename _Rep2>
-      inline duration<typename common_type<_Rep1, typename
+      inline duration<typename __common_rep_type<_Rep1, typename
 	enable_if<!__is_duration<_Rep2>::value, _Rep2>::type>::type, _Period>
       operator/(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
       {
@@ -394,7 +398,7 @@ namespace std
 
     // DR 934.
     template<typename _Rep1, typename _Period, typename _Rep2>
-      inline duration<typename common_type<_Rep1, typename
+      inline duration<typename __common_rep_type<_Rep1, typename
 	enable_if<!__is_duration<_Rep2>::value, _Rep2>::type>::type, _Period>
       operator%(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
       {
@@ -541,7 +545,8 @@ namespace std
   
     /// time_point_cast
     template<typename _ToDuration, typename _Clock, typename _Duration>
-      inline time_point<_Clock, _ToDuration> 
+      inline typename enable_if<__is_duration<_ToDuration>::value,
+				time_point<_Clock, _ToDuration>>::type
       time_point_cast(const time_point<_Clock, _Duration>& __t)
       {
         return time_point<_Clock, _ToDuration>(
diff --git a/libstdc++-v3/testsuite/20_util/duration/cons/1_neg.cc b/libstdc++-v3/testsuite/20_util/duration/cons/1_neg.cc
index 40d8219093e..56b4e4f413e 100644
--- a/libstdc++-v3/testsuite/20_util/duration/cons/1_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/cons/1_neg.cc
@@ -26,7 +26,7 @@
 void
 test01()
 {
-  std::chrono::duration<int> d1(1.0);
+  std::chrono::duration<int> d1(1.0); // { dg-error "no matching" }
 }
 
 void
@@ -35,11 +35,7 @@ test02()
   using namespace std::chrono;
   
   duration<int, std::micro> d2(8);
-  duration<int, std::milli> d2_copy(d2);
+  duration<int, std::milli> d2_copy(d2); // { dg-error "no matching" }
 }
 
-// { dg-error "instantiated from here" "" { target *-*-* } 29 }
-// { dg-error "instantiated from here" "" { target *-*-* } 38 }
-// { dg-error "not exactly representable" "" { target *-*-* } 227 }
-// { dg-error "integral duration with floating point" "" { target *-*-* } 217 }
-// { dg-excess-errors "In instantiation of" }
+// { dg-excess-errors "candidates are" }
diff --git a/libstdc++-v3/testsuite/20_util/duration/cons/dr974.cc b/libstdc++-v3/testsuite/20_util/duration/cons/dr974.cc
index 43132c9867c..4466d30097a 100644
--- a/libstdc++-v3/testsuite/20_util/duration/cons/dr974.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/cons/dr974.cc
@@ -29,9 +29,5 @@ void test01()
   using namespace std::chrono;
 
   duration<double> d(3.5);
-  duration<int> i = d;  // implicit truncation, should not compile
+  duration<int> i = d;  // { dg-error "conversion" }
 }
-
-// { dg-error "instantiated from here" "" { target *-*-* } 32 }
-// { dg-error "not exactly representable" "" { target *-*-* } 227 }
-// { dg-excess-errors "In instantiation of" }
diff --git a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
index e8b6d33a1ea..297b5cb690d 100644
--- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
@@ -31,6 +31,6 @@ void test01()
   test_type d;
 }
 
-// { dg-error "rep cannot be a duration" "" { target *-*-* } 202 }
+// { dg-error "rep cannot be a duration" "" { target *-*-* } 203 }
 // { dg-error "instantiated from here" "" { target *-*-* } 31 }
 // { dg-excess-errors "In instantiation of" }
diff --git a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
index 91081836779..b83bf494db5 100644
--- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
@@ -32,6 +32,6 @@ void test01()
   test_type d;
 }
 
-// { dg-error "must be a specialization of ratio" "" { target *-*-* } 203 }
+// { dg-error "must be a specialization of ratio" "" { target *-*-* } 204 }
 // { dg-error "instantiated from here" "" { target *-*-* } 32 }
 // { dg-excess-errors "In instantiation of" }
diff --git a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
index 540d72dde46..b4224401d47 100644
--- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
@@ -33,6 +33,6 @@ void test01()
   test_type d;
 }
 
-// { dg-error "period must be positive" "" { target *-*-* } 205 }
+// { dg-error "period must be positive" "" { target *-*-* } 206 }
 // { dg-error "instantiated from here" "" { target *-*-* } 33 }
 // { dg-excess-errors "In instantiation of" }