PR libstdc++/67554 Do not pass null pointers to memcpy

	PR libstdc++/67554
	* include/bits/valarray_array.h (_Array_copy_ctor<_Tp, true>)
	(_Array_copier<_Tp, true>): Do not pass null pointers to memcpy.

From-SVN: r260229

libstdc++-v3/ChangeLog

 2018-05-14  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/67554
+	* include/bits/valarray_array.h (_Array_copy_ctor<_Tp, true>)
+	(_Array_copier<_Tp, true>): Do not pass null pointers to memcpy.
+
 	PR libstdc++/82966
 	* include/bits/node_handle.h (_Node_handle_common::_M_swap): Use value
 	instead of type.

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

@@ -152,7 +152,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       inline static void
       _S_do_it(const _Tp* __b, const _Tp* __e, _Tp* __restrict__ __o)
-      { __builtin_memcpy(__o, __b, (__e - __b) * sizeof(_Tp)); }
+      {
+	if (__b)
+	  __builtin_memcpy(__o, __b, (__e - __b) * sizeof(_Tp));
+      }
     };
 
   template<typename _Tp>
@@ -258,7 +261,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       inline static void
       _S_do_it(const _Tp* __restrict__ __a, size_t __n, _Tp* __restrict__ __b)
-      { __builtin_memcpy(__b, __a, __n * sizeof (_Tp)); }
+      {
+	if (__n != 0)
+	  __builtin_memcpy(__b, __a, __n * sizeof (_Tp));
+      }
     };
 
   // Copy a plain array __a[<__n>] into a play array __b[<>]