Ensure std::thread helpers have internal linkage

	PR libstdc++/70503
	* src/c++11/thread.cc (execute_native_thread_routine,
	execute_native_thread_routine_compat): Give internal linkage.
	* testsuite/30_threads/thread/70503.cc: New test.

From-SVN: r234746

libstdc++-v3/ChangeLog

+2016-04-05  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/70503
+	* src/c++11/thread.cc (execute_native_thread_routine,
+	execute_native_thread_routine_compat): Give internal linkage.
+	* testsuite/30_threads/thread/70503.cc: New test.
+
 2016-04-05  Ville Voutilainen  <ville.voutilainen@gmail.com>
 
 	PR libstdc++/70437

libstdc++-v3/src/c++11/thread.cc

@@ -71,9 +71,9 @@ static inline int get_nprocs()
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
-  namespace
+  extern "C"
   {
-    extern "C" void*
+    static void*
     execute_native_thread_routine(void* __p)
     {
       thread::_State_ptr __t{ static_cast<thread::_State*>(__p) };
@@ -95,7 +95,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
     }
 
 #if _GLIBCXX_THREAD_ABI_COMPAT
-    extern "C" void*
+    static void*
     execute_native_thread_routine_compat(void* __p)
     {
       thread::_Impl_base* __t = static_cast<thread::_Impl_base*>(__p);
@@ -121,7 +121,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
       return nullptr;
     }
 #endif
-  }
+  } // extern "C"
 
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 

libstdc++-v3/testsuite/30_threads/thread/70503.cc

+// Copyright (C) 2016 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 link }
+// { dg-options " -std=gnu++11 -static" { target *-*-*gnu* } }
+// { dg-require-cstdint "" }
+// { dg-require-gthreads "" }
+
+extern "C" {
+  void execute_native_thread_routine(void);
+  void execute_native_thread_routine_compat(void);
+}
+
+int main()
+{
+  execute_native_thread_routine(); // { dg-error "undefined reference" }
+  execute_native_thread_routine_compat(); // { dg-error "undefined reference" }
+}
+// { dg-prune-output "collect2: error: ld returned" }