PR libstdc++/50834

[pf3gnuchains/gcc-fork.git] / libstdc++-v3 / src / locale_init.cc

diff --git a/libstdc++-v3/src/locale_init.cc b/libstdc++-v3/src/locale_init.cc
index 28ee484..98c228c 100644 (file)
--- a/libstdc++-v3/src/locale_init.cc
+++ b/libstdc++-v3/src/locale_init.cc
@@ -1,10 +1,11 @@
-// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
+// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 
+// 2009, 2010
 // 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 2, or (at your option)
+// 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,
@@ -12,19 +13,14 @@
 // 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 COPYING.  If not, write to the Free
-// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
-// USA.
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
 
-// As a special exception, you may use this file as part of a free software
-// library without restriction.  Specifically, if other files instantiate
-// templates or use macros or inline functions from this file, or you compile
-// this file and link it with other files to produce an executable, this
-// file does not by itself cause the resulting executable to be covered by
-// the GNU General Public License.  This exception does not however
-// invalidate any other reasons why the executable file might be covered by
-// the GNU General Public License.
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
 
 #include <clocale>
 #include <cstring>
@@ -207,14 +203,32 @@ namespace
 #endif
 } // anonymous namespace
 
-_GLIBCXX_BEGIN_NAMESPACE(std)
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   locale::locale() throw() : _M_impl(0)
   { 
     _S_initialize();
-    __gnu_cxx::__scoped_lock sentry(get_locale_mutex());
-    _S_global->_M_add_reference();
+
+    // Checked locking to optimize the common case where _S_global
+    // still points to _S_classic (locale::_S_initialize_once()):
+    // - If they are the same, just increment the reference count and
+    //   we are done.  This effectively constructs a C locale object
+    //   identical to the static c_locale.
+    // - Otherwise, _S_global can and may be destroyed due to
+    //   locale::global() call on another thread, in which case we
+    //   fall back to lock protected access to both _S_global and
+    //   its reference count.
     _M_impl = _S_global;
+    if (_M_impl == _S_classic)
+      _M_impl->_M_add_reference();
+    else
+      {
+        __gnu_cxx::__scoped_lock sentry(get_locale_mutex());
+        _S_global->_M_add_reference();
+        _M_impl = _S_global;
+      }
   }
 
   locale
@@ -242,19 +256,18 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 
   const locale&
   locale::classic()
-  {
+  { 
     _S_initialize();
-    return reinterpret_cast<const locale&>(c_locale);
+    return *(new (&c_locale) locale(_S_classic));
   }
 
   void
-  locale::_S_initialize_once()
+  locale::_S_initialize_once() throw()
   {
     // 2 references.
     // One reference for _S_classic, one for _S_global
     _S_classic = new (&c_locale_impl) _Impl(2);
     _S_global = _S_classic;        
-    new (&c_locale) locale(_S_classic);
   }
 
   void  
@@ -457,4 +470,5 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 #endif
   }
 
-_GLIBCXX_END_NAMESPACE
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace