re PR libstdc++/66327 (-fsanitize=nonnull-attribute errors in stl_algobase.h)

	PR libstdc++/66327
	* include/bits/stl_algobase.h (__equal<true>::equal): Do not call
	memcmp with null pointers.
	(__lexicographical_compare<true>::__lc): Do not call memcmp for empty
	ranges.

From-SVN: r223865

libstdc++-v3/ChangeLog

+2015-05-29  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/66327
+	* include/bits/stl_algobase.h (__equal<true>::equal): Do not call
+	memcmp with null pointers.
+	(__lexicographical_compare<true>::__lc): Do not call memcmp for empty
+	ranges.
+
 2015-05-28  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/65352

libstdc++-v3/include/bits/stl_algobase.h

@@ -812,6 +812,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
         static bool
         equal(const _Tp* __first1, const _Tp* __last1, const _Tp* __first2)
         {
+	  if (__first1 == 0 || __first2 == 0)
+	    return __first1 == __last1;
+
 	  return !__builtin_memcmp(__first1, __first2, sizeof(_Tp)
 				   * (__last1 - __first1));
 	}
@@ -917,9 +920,15 @@ _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 (__len1 && __len2)
+	    {
+	      if (int __result = __builtin_memcmp(__first1, __first2,
+						  std::min(__len1, __len2)))
+		{
+		  return __result < 0;
+		}
+	    }
+	  return __len1 < __len2;
 	}
     };