diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index b6a69e3e6ea4..b675f5ffab50 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,14 @@
 2015-06-08  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/66354
+	* include/bits/stl_algobase.h (__fill_a): Check length before calling
+	memset.
+
+	PR libstdc++/66327
+	* include/bits/stl_algobase.h (__equal<true>::equal): Do not call
+	memcmp for empty ranges.
+	(__lexicographical_compare<true>::__lc): Likewise.
+
 	Backported from mainline
 	2015-06-02  Jonathan Wakely  <jwakely@redhat.com>
 
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index 90401350d949..2b69e6189545 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -715,8 +715,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     __fill_a(_Tp* __first, _Tp* __last, const _Tp& __c)
     {
       const _Tp __tmp = __c;
-      __builtin_memset(__first, static_cast<unsigned char>(__tmp),
-		       __last - __first);
+      if (const size_t __len = __last - __first)
+	__builtin_memset(__first, static_cast<unsigned char>(__tmp), __len);
     }
 
   /**
@@ -822,8 +822,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
         static bool
         equal(const _Tp* __first1, const _Tp* __last1, const _Tp* __first2)
         {
-	  return !__builtin_memcmp(__first1, __first2, sizeof(_Tp)
-				   * (__last1 - __first1));
+	  if (const size_t __len = (__last1 - __first1))
+	    return !__builtin_memcmp(__first1, __first2, sizeof(_Tp) * __len);
+	  return true;
 	}
     };
 
@@ -927,9 +928,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{
 	  const size_t __len1 = __last1 - __first1;
 	  const size_t __len2 = __last2 - __first2;
-	  const int __result = __builtin_memcmp(__first1, __first2,
-						std::min(__len1, __len2));
-	  return __result != 0 ? __result < 0 : __len1 < __len2;
+	  if (const size_t __len = std::min(__len1, __len2))
+	    if (int __result = __builtin_memcmp(__first1, __first2, __len))
+	      return __result < 0;
+	  return __len1 < __len2;
 	}
     };