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

[Jonathan Wakely]

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

Tested powerpc64le-linux, committed to trunk.

Backports to follow.

There's no new test for this, as we're not able to use sanitizers in
the testsuite (something I still hope to fix one day).

-------------- next part --------------
commit cd61c4ce0bfd69065018417dfe6f3e03b2010af3
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon May 14 15:50:16 2018 +0100

    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.

diff --git a/libstdc++-v3/include/bits/valarray_array.h b/libstdc++-v3/include/bits/valarray_array.h
index f1d2c43044f..07f38ed03ed 100644
--- a/libstdc++-v3/include/bits/valarray_array.h
+++ b/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[<>]