commit b639a9cac6e2532eb852b03df6ac40d34f1dd28c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Feb 22 20:33:16 2019 +0000

    PR libstdc++/89446 fix null pointer dereference in char_traits
    
            PR libstdc++/89446
            * include/bits/char_traits.h (__constant_char_array): Check index is
            in range before dereferencing.
            * testsuite/21_strings/basic_string_view/operators/char/89446.cc:
            New test.

diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h
index 1945494d7e2..a2a883f3565 100644
--- a/libstdc++-v3/include/bits/char_traits.h
+++ b/libstdc++-v3/include/bits/char_traits.h
@@ -248,7 +248,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     __constant_char_array_p(const _CharT* __a, size_t __n)
     {
       size_t __i = 0;
-      while (__builtin_constant_p(__a[__i]) && __i < __n)
+      while (__i < __n && __builtin_constant_p(__a[__i]))
 	__i++;
       return __i == __n;
     }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operators/char/89446.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operators/char/89446.cc
new file mode 100644
index 00000000000..768ba63ddfe
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operators/char/89446.cc
@@ -0,0 +1,28 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17 -fexceptions -fnon-call-exceptions -O1" }
+// { dg-do run { target { powerpc*-*-linux* i?86-*-linux* x86_64-*-linux* } } }
+// { dg-require-effective-target c++17 }
+
+#include <string_view>
+
+int main()
+{
+  std::string_view s1, s2;
+  return s1 != s2;
+}