PR libstdc++/85494 use rand_s in std::random_device

diff --git a/libstdc++-v3/config/os/mingw32-w64/os_defines.h b/libstdc++-v3/config/os/mingw32-w64/os_defines.h
index 6c19d3953a6..418c6f569df 100644
--- a/libstdc++-v3/config/os/mingw32-w64/os_defines.h
+++ b/libstdc++-v3/config/os/mingw32-w64/os_defines.h
@@ -88,4 +88,6 @@ 
 // See libstdc++/59807
 #define _GTHREAD_USE_MUTEX_INIT_FUNC 1
 
+#define _GLIBCXX_USE_CRT_RAND_S 1
+
 #endif
diff --git a/libstdc++-v3/src/c++11/cow-string-inst.cc b/libstdc++-v3/src/c++11/cow-string-inst.cc
index c36f297438e..a5e4ad29dc3 100644
--- a/libstdc++-v3/src/c++11/cow-string-inst.cc
+++ b/libstdc++-v3/src/c++11/cow-string-inst.cc
@@ -77,8 +77,9 @@  namespace std _GLIBCXX_VISIBILITY(default)
   }
 
   void
-  random_device::_M_init_pretr1(const std::string& token)
+  random_device::_M_init_pretr1(const std::string& token [[gnu::unused]])
   {
+#ifndef _GLIBCXX_USE_CRT_RAND_S
     unsigned long __seed = 5489UL;
     if (token != "mt19937")
       {
@@ -90,6 +91,7 @@  namespace std _GLIBCXX_VISIBILITY(default)
 					 "(const std::string&)"));
       }
     _M_mt.seed(__seed);
+#endif
   }
 } // namespace
 #endif
diff --git a/libstdc++-v3/src/c++11/random.cc b/libstdc++-v3/src/c++11/random.cc
index 1146d21c3f9..0bb6b6bf5b8 100644
--- a/libstdc++-v3/src/c++11/random.cc
+++ b/libstdc++-v3/src/c++11/random.cc
@@ -23,6 +23,8 @@ 
 // <http://www.gnu.org/licenses/>.
 
 #define _GLIBCXX_USE_CXX11_ABI 1
+#define _CRT_RAND_S // define this before including <stdlib.h> to get rand_s
+
 #include <random>
 
 #ifdef  _GLIBCXX_USE_C99_STDINT_TR1
@@ -50,6 +52,10 @@ 
 # include <linux/random.h>
 #endif
 
+#ifdef _GLIBCXX_USE_CRT_RAND_S
+# include <stdlib.h>
+#endif
+
 namespace std _GLIBCXX_VISIBILITY(default)
 {
   namespace
@@ -85,6 +91,18 @@  namespace std _GLIBCXX_VISIBILITY(default)
       return val;
     }
 #endif
+
+#ifdef _GLIBCXX_USE_CRT_RAND_S
+# pragma GCC poison _M_mt
+    unsigned int
+    __winxp_rand_s()
+    {
+      unsigned int val;
+      if (::rand_s(&val) != 0)
+	std::__throw_runtime_error(__N("random_device: rand_s failed"));
+      return val;
+    }
+#endif
   }
 
   void
@@ -122,9 +140,11 @@  namespace std _GLIBCXX_VISIBILITY(default)
   }
 
   void
-  random_device::_M_init_pretr1(const std::string& token)
+  random_device::_M_init_pretr1(const std::string& token [[gnu::unused]])
   {
+#ifndef _GLIBCXX_USE_CRT_RAND_S
     _M_mt.seed(_M_strtoul(token));
+#endif
   }
 
   void
@@ -170,7 +190,11 @@  namespace std _GLIBCXX_VISIBILITY(default)
   random_device::result_type
   random_device::_M_getval_pretr1()
   {
+#ifdef _GLIBCXX_USE_CRT_RAND_S
+    return __winxp_rand_s();
+#else
     return _M_mt();
+#endif
   }
 
   double
diff --git a/libstdc++-v3/testsuite/26_numerics/random/random_device/85494.cc b/libstdc++-v3/testsuite/26_numerics/random/random_device/85494.cc
new file mode 100644
index 00000000000..2670ad7225a
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/random/random_device/85494.cc
@@ -0,0 +1,40 @@ 
+// 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-do run { target c++11 } }
+// { dg-require-effective-target random_device }
+
+#include <random>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  unsigned v1[3], v2[3];
+  std::random_device d1, d2;
+  for (auto& v : v1)
+    v = d1();
+  for (auto& v : v2)
+    v = d2();
+  VERIFY (v1[0] != v2[0] || v1[1] != v2[1] || v1[2] != v2[2] );
+}
+
+int
+main()
+{
+  test01();
+}