patch: _Atomic_swap implementation for g++-v3/bits/stl_threads.h

[Dimitris Vyzovitis <vyzo at media dot mit dot edu>]

Hi,

here is a patch for g++-v3/bits/stl_threads.h which provides _Atomic_swap 
with gthreads. 
It's a simple patch (direct conversion of the pthread code), but it 
nevertheless makes ropes usable again in a threaded environment.

-- dimitris
   mailto:vyzo@media.mit.edu
--- stl_threads.h.old	Wed Sep 19 19:05:26 2001
+++ stl_threads.h	Wed Sep 19 20:44:50 2001
@@ -202,6 +202,28 @@
 // later, if required.  You can start by cloning the __STL_PTHREADS
 // path while making the obvious changes.  Later it could be optimized
 // to use the atomicity.h abstraction layer from libstdc++-v3.
+// vyzo: simple _Atomic_swap implementation following the guidelines above
+	// We use a template here only to get a unique initialized instance.
+    template<int __dummy>
+    struct _Swap_lock_struct {
+        static __gthread_mutex_t _S_swap_lock;
+    };
+
+    template<int __dummy>
+    __gthread_mutex_t
+    _Swap_lock_struct<__dummy>::_S_swap_lock = __GTHREAD_MUTEX_INIT;
+
+    // This should be portable, but performance is expected
+    // to be quite awful.  This really needs platform specific
+    // code.
+    inline unsigned long _Atomic_swap(unsigned long * __p, unsigned long __q) {
+        __gthread_mutex_lock(&_Swap_lock_struct<0>::_S_swap_lock);
+        unsigned long __result = *__p;
+        *__p = __q;
+        __gthread_mutex_unlock(&_Swap_lock_struct<0>::_S_swap_lock);
+        return __result;
+    }
+
 #else
 // GCC extension end
 # ifdef __STL_SGI_THREADS