New function: g_clear_object()

By analogy to g_clear_error, takes a pass-by-reference GObject reference
and, if non-%NULL, unrefs it and sets it equal to %NULL.

Bug #620263.
This commit is contained in:
Ryan Lortie 2010-11-08 16:42:32 -05:00
parent 78bc8bec4f
commit 1a1fc130ec
7 changed files with 93 additions and 1 deletions

View File

@ -257,6 +257,7 @@ GParameter
g_object_ref
g_object_unref
g_object_ref_sink
g_clear_object
GInitiallyUnowned
GInitiallyUnownedClass
G_TYPE_INITIALLY_UNOWNED

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@ -2728,6 +2728,44 @@ g_object_unref (gpointer _object)
}
}
/**
* g_clear_object:
* @object_ptr: a pointer to a #GObject reference
*
* Clears a reference to a #GObject.
*
* @object_ptr must not be %NULL.
*
* If the reference is %NULL then this function does nothing.
* Otherwise, the reference count of the object is decreased and the
* pointer is set to %NULL.
*
* This function is threadsafe and modifies the pointer atomically,
* using memory barriers where needed.
*
* A macro is also included that allows this function to be used without
* pointer casts.
*
* Since: 2.28
**/
#undef g_clear_object
void
g_clear_object (volatile GObject **object_ptr)
{
gpointer *ptr = (gpointer) object_ptr;
gpointer old;
/* This is a little frustrating.
* Would be nice to have an atomic exchange (with no compare).
*/
do
old = g_atomic_pointer_get (ptr);
while G_UNLIKELY (!g_atomic_pointer_compare_and_exchange (ptr, old, NULL));
if (old)
g_object_unref (old);
}
/**
* g_object_get_qdata:
* @object: The GObject to get a stored user data pointer from

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@ -562,6 +562,21 @@ G_STMT_START { \
#define G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, pspec) \
G_OBJECT_WARN_INVALID_PSPEC ((object), "property", (property_id), (pspec))
void g_clear_object (volatile GObject **object_ptr);
#define g_clear_object(object_ptr) \
G_STMT_START { \
/* Only one access, please */ \
gpointer *_p = (gpointer) (object_ptr); \
gpointer _o; \
\
do \
_o = g_atomic_pointer_get (_p); \
while G_UNLIKELY (!g_atomic_pointer_compare_and_exchange (_p, _o, NULL));\
\
if (_o) \
g_object_unref (_o); \
} G_STMT_END
G_END_DECLS
#endif /* __G_OBJECT_H__ */

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@ -186,6 +186,7 @@ g_value_get_object
g_value_set_object
g_value_dup_object
g_value_take_object
g_clear_object
#ifndef G_DISABLE_DEPRECATED
g_value_set_object_take_ownership
g_object_compat_control

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@ -1,4 +1,5 @@
binding
dynamictests
properties
reference
threadtests

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@ -5,7 +5,7 @@ INCLUDES = -g $(gobject_INCLUDES) $(GLIB_DEBUG_FLAGS)
noinst_PROGRAMS = $(TEST_PROGS)
libgobject_LDADD = ../libgobject-2.0.la $(top_builddir)/gthread/libgthread-2.0.la $(top_builddir)/glib/libglib-2.0.la
TEST_PROGS += threadtests dynamictests binding properties
TEST_PROGS += threadtests dynamictests binding properties reference
threadtests_SOURCES = threadtests.c
threadtests_LDADD = $(libgobject_LDADD)
dynamictests_SOURCES = dynamictests.c
@ -14,3 +14,4 @@ binding_SOURCES = binding.c
binding_LDADD = $(libgobject_LDADD)
properties_SOURCES = properties.c
properties_LDADD = $(libgobject_LDADD)
reference_LDADD = $(libgobject_LDADD)

35
gobject/tests/reference.c Normal file
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@ -0,0 +1,35 @@
#include <glib-object.h>
static void
test_clear (void)
{
GObject *o = NULL;
GObject *tmp;
g_clear_object (&o);
g_assert (o == NULL);
tmp = g_object_new (G_TYPE_OBJECT, NULL);
g_assert_cmpint (tmp->ref_count, ==, 1);
o = g_object_ref (tmp);
g_assert (o != NULL);
g_assert_cmpint (tmp->ref_count, ==, 2);
g_clear_object (&o);
g_assert_cmpint (tmp->ref_count, ==, 1);
g_assert (o == NULL);
g_object_unref (tmp);
}
int
main (int argc, char **argv)
{
g_test_init (&argc, &argv, NULL);
g_type_init ();
g_test_add_func ("/object/clear", test_clear);
return g_test_run ();
}