c++config (_GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE, [...]): Add.

2010-08-12  Kostya Serebryany <kcc@google.com>
	    Paolo Carlini  <paolo.carlini@oracle.com>

	* include/bits/c++config (_GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE,
	_GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER): Add.
	* src/ios_init.cc (ios_base::Init::~Init): Decorate with the
	latter.
	* include/tr1_impl/boost_sp_counted_base.h: Likewise.
	* include/ext/rc_string_base.h: Likewise.
	* include/bits/locale_classes.h: Likewise.
	* include/bits/basic_string.h: Likewise.
	* include/bits/ios_base.h: Likewise.
	* testsuite/27_io/ios_base/cons/assign_neg.cc: Adjust dg-error
	line number.
	* testsuite/27_io/ios_base/cons/copy_neg.cc: Likewise.
	* testsuite/ext/profile/mutex_extensions.cc: Likewise.

Co-Authored-By: Paolo Carlini <paolo.carlini@oracle.com>

From-SVN: r163210

11 files changed, 101 insertions, 13 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 84d3598..f133c0a 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,20 @@
+2010-08-12  Kostya Serebryany <kcc@google.com>
+	    Paolo Carlini  <paolo.carlini@oracle.com>
+
+	* include/bits/c++config (_GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE,
+	_GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER): Add.
+	* src/ios_init.cc (ios_base::Init::~Init): Decorate with the
+	latter.
+	* include/tr1_impl/boost_sp_counted_base.h: Likewise.
+	* include/ext/rc_string_base.h: Likewise.
+	* include/bits/locale_classes.h: Likewise.
+	* include/bits/basic_string.h: Likewise.
+	* include/bits/ios_base.h: Likewise.
+	* testsuite/27_io/ios_base/cons/assign_neg.cc: Adjust dg-error
+	line number.
+	* testsuite/27_io/ios_base/cons/copy_neg.cc: Likewise.
+	* testsuite/ext/profile/mutex_extensions.cc: Likewise.
+
 2010-08-11  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* include/bits/hashtable.h (_Hashtable<>::erase(const key_type&)):
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index fe9e1a3..74820eb 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -232,9 +232,16 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
 	  if (__builtin_expect(this != &_S_empty_rep(), false))
 #endif
-	    if (__gnu_cxx::__exchange_and_add_dispatch(&this->_M_refcount,
-						       -1) <= 0)
-	      _M_destroy(__a);
+	    {
+	      // Be race-detector-friendly.  For more info see bits/c++config.
+	      _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&this->_M_refcount)
+	      if (__gnu_cxx::__exchange_and_add_dispatch(&this->_M_refcount,
+							 -1) <= 0)
+		{
+		  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&this->_M_refcount)
+		  _M_destroy(__a);
+		}
+	    }
 	}  // XXX MT
 
 	void
diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 9dc9ac2..fef6933 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -60,6 +60,35 @@
 # define _GLIBCXX_DEPRECATED_ATTR
 #endif
 
+// Macros for race detectors.
+// _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(A) and
+// _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(A) should be used to explain
+// atomic (lock-free) synchronization to race detectors:
+// the race detector will infer a happens-before arc from the former to the
+// latter when they share the same argument pointer.
+//
+// The most frequent use case for these macros (and the only case in the
+// current implementation of the library) is atomic reference counting:
+//   void _M_remove_reference()
+//   {
+//     _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&this->_M_refcount)
+//     if (__gnu_cxx::__exchange_and_add_dispatch(&this->_M_refcount, -1) <= 0)
+//       {
+//         _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&this->_M_refcount)
+//         _M_destroy(__a);
+//       }
+//   }
+// The annotations in this example tell the race detector that all memory
+// accesses occurred when the refcount was positive do not race with
+// memory accesses which occurred after the refcount became zero.
+
+#ifndef _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE
+# define  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(A)
+#endif
+#ifndef _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER
+# define  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(A)
+#endif
+
 // Macros for activating various namespace association modes.
 // _GLIBCXX_NAMESPACE_ASSOCIATION_DEBUG
 // _GLIBCXX_NAMESPACE_ASSOCIATION_PARALLEL
diff --git a/libstdc++-v3/include/bits/ios_base.h b/libstdc++-v3/include/bits/ios_base.h
index 6515dd4..6cca991 100644
--- a/libstdc++-v3/include/bits/ios_base.h
+++ b/libstdc++-v3/include/bits/ios_base.h
@@ -474,7 +474,16 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
       // 0 => OK to delete.
       int
       _M_remove_reference() 
-      { return __gnu_cxx::__exchange_and_add_dispatch(&_M_refcount, -1); }
+      {
+        // Be race-detector-friendly.  For more info see bits/c++config.
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_refcount)
+        int __res = __gnu_cxx::__exchange_and_add_dispatch(&_M_refcount, -1);
+        if (__res == 0)
+          {
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_refcount)
+          }
+        return __res;
+      }
     };
 
      _Callback_list*	_M_callbacks;
@@ -962,4 +971,3 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 _GLIBCXX_END_NAMESPACE
 
 #endif /* _IOS_BASE_H */
-
diff --git a/libstdc++-v3/include/bits/locale_classes.h b/libstdc++-v3/include/bits/locale_classes.h
index 347e761..c519f35 100644
--- a/libstdc++-v3/include/bits/locale_classes.h
+++ b/libstdc++-v3/include/bits/locale_classes.h
@@ -402,8 +402,11 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     void
     _M_remove_reference() const throw()
     {
+      // Be race-detector-friendly.  For more info see bits/c++config.
+      _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_refcount)
       if (__gnu_cxx::__exchange_and_add_dispatch(&_M_refcount, -1) == 1)
 	{
+          _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_refcount)
 	  __try
 	    { delete this; }
 	  __catch(...)
@@ -508,8 +511,11 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     void
     _M_remove_reference() throw()
     {
+      // Be race-detector-friendly.  For more info see bits/c++config.
+      _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_refcount)
       if (__gnu_cxx::__exchange_and_add_dispatch(&_M_refcount, -1) == 1)
 	{
+          _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_refcount)
 	  __try
 	    { delete this; }
 	  __catch(...)
diff --git a/libstdc++-v3/include/ext/rc_string_base.h b/libstdc++-v3/include/ext/rc_string_base.h
index dd18738..32c9d38 100644
--- a/libstdc++-v3/include/ext/rc_string_base.h
+++ b/libstdc++-v3/include/ext/rc_string_base.h
@@ -199,9 +199,16 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
       void
       _M_dispose()
       {
+	// Be race-detector-friendly.  For more info see bits/c++config.
+	_GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_rep()->_M_info.
+						_M_refcount)
 	if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount,
 					-1) <= 0)
-	  _M_rep()->_M_destroy(_M_get_allocator());
+	  {
+	    _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_rep()->_M_info.
+						   _M_refcount)
+	    _M_rep()->_M_destroy(_M_get_allocator());
+	  }
       }  // XXX MT
 
       bool
diff --git a/libstdc++-v3/include/tr1_impl/boost_sp_counted_base.h b/libstdc++-v3/include/tr1_impl/boost_sp_counted_base.h
index 5603085..a995df5 100644
--- a/libstdc++-v3/include/tr1_impl/boost_sp_counted_base.h
+++ b/libstdc++-v3/include/tr1_impl/boost_sp_counted_base.h
@@ -1,6 +1,6 @@
 // <tr1_impl/boost_sp_counted_base.h> -*- C++ -*-
 
-// Copyright (C) 2007, 2009 Free Software Foundation, Inc.
+// Copyright (C) 2007, 2008, 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
@@ -139,8 +139,11 @@ _GLIBCXX_BEGIN_NAMESPACE_TR1
       void
       _M_release() // nothrow
       {
+        // Be race-detector-friendly.  For more info see bits/c++config.
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count)
 	if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
 	  {
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count)
 	    _M_dispose();
 	    // There must be a memory barrier between dispose() and destroy()
 	    // to ensure that the effects of dispose() are observed in the
@@ -152,9 +155,14 @@ _GLIBCXX_BEGIN_NAMESPACE_TR1
 	        _GLIBCXX_WRITE_MEM_BARRIER;
 	      }
 
+            // Be race-detector-friendly.  For more info see bits/c++config.
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count)
 	    if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,
 						       -1) == 1)
-	      _M_destroy();
+              {
+                _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count)
+	        _M_destroy();
+              }
 	  }
       }
   
@@ -165,8 +173,11 @@ _GLIBCXX_BEGIN_NAMESPACE_TR1
       void
       _M_weak_release() // nothrow
       {
+        // Be race-detector-friendly. For more info see bits/c++config.
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count)
 	if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1)
 	  {
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count)
 	    if (_Mutex_base<_Lp>::_S_need_barriers)
 	      {
 	        // See _M_release(),
diff --git a/libstdc++-v3/src/ios_init.cc b/libstdc++-v3/src/ios_init.cc
index 1885d82..209a324 100644
--- a/libstdc++-v3/src/ios_init.cc
+++ b/libstdc++-v3/src/ios_init.cc
@@ -1,7 +1,7 @@
 // Iostreams base classes -*- C++ -*-
 
 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
-// 2006, 2007, 2008, 2009
+// 2006, 2007, 2008, 2009, 2010
 // Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
@@ -122,8 +122,11 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 
   ios_base::Init::~Init()
   {
+    // Be race-detector-friendly.  For more info see bits/c++config.
+    _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_S_refcount)
     if (__gnu_cxx::__exchange_and_add_dispatch(&_S_refcount, -1) == 2)
       {
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_S_refcount)
 	// Catch any exceptions thrown by basic_ostream::flush()
 	__try
 	  { 
diff --git a/libstdc++-v3/testsuite/27_io/ios_base/cons/assign_neg.cc b/libstdc++-v3/testsuite/27_io/ios_base/cons/assign_neg.cc
index 9f85ad1..a7adff4 100644
--- a/libstdc++-v3/testsuite/27_io/ios_base/cons/assign_neg.cc
+++ b/libstdc++-v3/testsuite/27_io/ios_base/cons/assign_neg.cc
@@ -34,5 +34,5 @@ void test01()
 }
 // { dg-error "synthesized" "" { target *-*-* } 33 } 
 // { dg-error "within this context" "" { target *-*-* } 26 } 
-// { dg-error "is private" "" { target *-*-* } 779 }
+// { dg-error "is private" "" { target *-*-* } 788 }
 // { dg-error "operator=" "" { target *-*-* } 0 } 
diff --git a/libstdc++-v3/testsuite/27_io/ios_base/cons/copy_neg.cc b/libstdc++-v3/testsuite/27_io/ios_base/cons/copy_neg.cc
index 2a75737..44f7af8 100644
--- a/libstdc++-v3/testsuite/27_io/ios_base/cons/copy_neg.cc
+++ b/libstdc++-v3/testsuite/27_io/ios_base/cons/copy_neg.cc
@@ -34,5 +34,5 @@ void test02()
 }
 // { dg-error "within this context" "" { target *-*-* } 26 }
 // { dg-error "synthesized" "" { target *-*-* } 33 } 
-// { dg-error "is private" "" { target *-*-* } 776 } 
+// { dg-error "is private" "" { target *-*-* } 785 } 
 // { dg-error "copy constructor" "" { target *-*-* } 0 } 
diff --git a/libstdc++-v3/testsuite/ext/profile/mutex_extensions.cc b/libstdc++-v3/testsuite/ext/profile/mutex_extensions.cc
index 4b30661..471c448 100644
--- a/libstdc++-v3/testsuite/ext/profile/mutex_extensions.cc
+++ b/libstdc++-v3/testsuite/ext/profile/mutex_extensions.cc
@@ -3,7 +3,7 @@
 
 // -*- C++ -*-
 
-// Copyright (C) 2006, 2007, 2009 Free Software Foundation, Inc.
+// Copyright (C) 2006, 2007, 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
@@ -22,4 +22,4 @@
 
 #include <vector>
 
-// { dg-error "Cannot use -D_GLIBCXX_PROFILE with " "" { target *-*-* } 167 }
+// { dg-error "Cannot use -D_GLIBCXX_PROFILE with " "" { target *-*-* } 196 }