[m-dev.] diff: fix memory leak in semaphore.m

[Peter Ross]

Hi,

Found the memory leak!
The reason why it only showed up under Windows was because linux
pthreads don't do any allocate any resources for a condvars and mutexs
so they don't need to be explicitly destroyed.

===================================================================


Estimated hours taken: 32

Fix a memory leak in semaphore.m

extras/concurrency/semaphore.m:
	Semaphores use pthread condvars and mutexs for their underlying
	implementation.  These need to be explicitly destroyed when the
	semaphore is garbage collected.  This is done by registering a
	finalization routine for the semaphore.


Index: semaphore.m
===================================================================
RCS file: /home/mercury1/repository/mercury/extras/concurrency/semaphore.m,v
retrieving revision 1.3
diff -u -r1.3 semaphore.m
--- semaphore.m	2000/09/08 09:14:54	1.3
+++ semaphore.m	2000/09/13 13:50:23
@@ -89,9 +89,38 @@
 #ifdef MR_THREAD_SAFE
 	pthread_mutex_init(&(sem->lock), MR_MUTEX_ATTR);
 #endif
+
+	/*
+	** The condvar and the mutex will need to be destroyed
+	** when the semaphore is garbage collected.
+	*/
+#ifdef CONSERVATIVE_GC
+	GC_REGISTER_FINALIZER(sem, finalize_semaphore, NULL, NULL, NULL);
+#endif
+
 	Semaphore = (MR_Word) sem;
 	IO = IO0;
 }").
+
+:- pragma c_code("
+#ifdef CONSERVATIVE_GC
+  void finalize_semaphore(GC_PTR obj, GC_PTR cd)
+  {
+	ME_Semaphore    *sem;
+
+	sem = (ME_Semaphore *) obj;
+
+  #ifdef MR_HIGHLEVEL_CODE
+	pthread_cond_destroy(&(sem->cond));
+  #endif
+  #ifdef MR_THREAD_SAFE
+	pthread_mutex_destroy(&(sem->lock));
+  #endif
+
+	return;
+  }
+#endif
+").
 
 		% because semaphore__signal has a local label, we may get
 		% C compilation errors if inlining leads to multiple copies

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