re PR libstdc++/12855 (Thread safety problems in ios_base::Init)

2003-12-15  Benjamin Kosnik  <bkoz@redhat.com>

	PR libstdc++/12855
	* include/bits/ios_base.h (Init::_S_ios_base_init): Change to
	_S_refcount, make atomic.
	* src/ios.cc: Adjust definition.
	* src/ios_init.cc (ios_base::Init::Init): Use __exchange_and_add,
	and __atomic_add.
	(ios_base::Init::~Init): Same.
	* testsuite/27_io/ios_base/cons/assign_neg.cc: Adjust line numbers.
	* testsuite/27_io/ios_base/cons/copy_neg.cc: Same.

From-SVN: r74642

6 files changed, 27 insertions, 13 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index e0f17c3..c64b3aa 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,15 @@
+2003-12-15  Benjamin Kosnik  <bkoz@redhat.com>
+
+	PR libstdc++/12855	
+	* include/bits/ios_base.h (Init::_S_ios_base_init): Change to
+	_S_refcount, make atomic.
+	* src/ios.cc: Adjust definition.	
+	* src/ios_init.cc (ios_base::Init::Init): Use __exchange_and_add,
+	and __atomic_add.
+	(ios_base::Init::~Init): Same.
+	* testsuite/27_io/ios_base/cons/assign_neg.cc: Adjust line numbers.
+	* testsuite/27_io/ios_base/cons/copy_neg.cc: Same.
+	
 2003-12-15  Paolo Carlini  <pcarlini@suse.de>
 
 	* include/bits/locale_facets.tcc (num_get::do_get(bool&)):
diff --git a/libstdc++-v3/include/bits/ios_base.h b/libstdc++-v3/include/bits/ios_base.h
index 5455dd2..e2d3fba 100644
--- a/libstdc++-v3/include/bits/ios_base.h
+++ b/libstdc++-v3/include/bits/ios_base.h
@@ -493,14 +493,13 @@ namespace std
       ~Init();
       
       // NB: Allows debugger applications use of the standard streams
-      // from operator new. _S_ios_base_init must be incremented in
-      // _S_ios_create _after_ initialization is completed.
+      // from operator new. 
       static bool
-      _S_initialized() { return _S_ios_base_init; }
+      _S_initialized() { return _S_refcount > 0; }
 
     private:
-      static int 	_S_ios_base_init;
-      static bool	_S_synced_with_stdio;
+      static _Atomic_word	_S_refcount;
+      static bool		_S_synced_with_stdio;
     };
 
     // [27.4.2.2] fmtflags state functions
diff --git a/libstdc++-v3/src/ios.cc b/libstdc++-v3/src/ios.cc
index fdc1f06..b36165e 100644
--- a/libstdc++-v3/src/ios.cc
+++ b/libstdc++-v3/src/ios.cc
@@ -107,7 +107,7 @@ namespace std
 
   const int ios_base::_S_local_word_size;
 
-  int ios_base::Init::_S_ios_base_init = 0;
+  _Atomic_word ios_base::Init::_S_refcount;
 
   bool ios_base::Init::_S_synced_with_stdio = true;
 
diff --git a/libstdc++-v3/src/ios_init.cc b/libstdc++-v3/src/ios_init.cc
index 1645ea7..b402025 100644
--- a/libstdc++-v3/src/ios_init.cc
+++ b/libstdc++-v3/src/ios_init.cc
@@ -80,7 +80,7 @@ namespace std
 
   ios_base::Init::Init()
   {
-    if (_S_ios_base_init == 0)
+    if (__exchange_and_add(&_S_refcount, 1) == 0)
       {
 	// Standard streams default to synced with "C" operations.
 	_S_synced_with_stdio = true;
@@ -110,15 +110,18 @@ namespace std
 	wcin.tie(&wcout);
 	wcerr.flags(ios_base::unitbuf);
 #endif
-
-	_S_ios_base_init = 1;
+	
+	// NB: Have to set refcount above one, so that standard
+	// streams are not re-initialized with uses of ios_base::Init
+	// besides <iostream> static object, ie just using <ios> with
+	// ios_base::Init objects.
+	__atomic_add(&_S_refcount, 1);
       }
-    ++_S_ios_base_init;
   }
 
   ios_base::Init::~Init()
   {
-    if (--_S_ios_base_init == 1)
+    if (__exchange_and_add(&_S_refcount, -1) == 2)
       {
 	// 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 ae7ba3c..3261c07 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
@@ -41,5 +41,5 @@ void test01()
   io1 = io2;
 }
 // { dg-error "within this context" "" { target *-*-* } 41 } 
-// { dg-error "is private" "" { target *-*-* } 746 } 
+// { dg-error "is private" "" { target *-*-* } 745 } 
 // { 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 9dfde27..5f8871f 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
@@ -41,5 +41,5 @@ void test02()
   test_base io2 = io1; 
 }
 // { dg-error "within this context" "" { target *-*-* } 41 } 
-// { dg-error "is private" "" { target *-*-* } 743 } 
+// { dg-error "is private" "" { target *-*-* } 742 } 
 // { dg-error "copy constructor" "" { target *-*-* } 0 }