util: alloc: Introduce VIR_AUTOUNREF macro

Add helper for utilizing __attribute__(cleanup())) for unref-ing
instances of sublasses of virObject.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

src/libvirt_private.syms

@@ -2511,6 +2511,7 @@ virClassForObjectRWLockable;
 virClassIsDerivedFrom;
 virClassName;
 virClassNew;
+virObjectAutoUnref;
 virObjectFreeCallback;
 virObjectFreeHashData;
 virObjectIsClass;

src/util/viralloc.h

@@ -637,4 +637,14 @@ void virAllocTestHook(void (*func)(int, void*), void *data);
 # define VIR_AUTOPTR(type) \
     __attribute__((cleanup(VIR_AUTOPTR_FUNC_NAME(type)))) type *
 
+/**
+ * VIR_AUTOUNREF:
+ * @type: type of an virObject subclass to be unref'd automatically
+ *
+ * Declares a variable of @type which will be automatically unref'd when
+ * control goes out of the scope.
+ */
+# define VIR_AUTOUNREF(type) \
+    __attribute__((cleanup(virObjectAutoUnref))) type
+
 #endif /* LIBVIRT_VIRALLOC_H */

src/util/virobject.c

@@ -362,6 +362,19 @@ virObjectUnref(void *anyobj)
 }
 
 
+/**
+ * virObjectAutoUnref:
+ *
+ * Helper used by VIR_AUTOUNREF
+ */
+void
+virObjectAutoUnref(void *objptr)
+{
+    virObjectPtr *obj = objptr;
+    virObjectUnref(*obj);
+}
+
+
 /**
  * virObjectRef:
  * @anyobj: any instance of virObjectPtr

src/util/virobject.h

@@ -102,6 +102,9 @@ virObjectNew(virClassPtr klass)
 bool
 virObjectUnref(void *obj);
 
+void
+virObjectAutoUnref(void *objptr);
+
 void *
 virObjectRef(void *obj);