[kdbus] Do not set body message if signature field is empty
[platform/upstream/glib.git] / gobject / gclosure.c
index 3fc3387..8d0d656 100644 (file)
@@ -1,5 +1,6 @@
 /* GObject - GLib Type, Object, Parameter and Signal Library
  * Copyright (C) 2000-2001 Red Hat, Inc.
+ * Copyright (C) 2005 Imendio AB
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General
- * Public License along with this library; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
- * Boston, MA 02111-1307, USA.
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 
-#include       "gclosure.h"
+/*
+ * MT safe with regards to reference counting.
+ */
+
+#include "config.h"
+
+#include <string.h>
 
-#include       "gvalue.h"
-#include       <string.h>
+#include <ffi.h>
 
+#include "gclosure.h"
+#include "gboxed.h"
+#include "gobject.h"
+#include "genums.h"
+#include "gvalue.h"
+#include "gvaluetypes.h"
+#include "gtype-private.h"
 
-/* FIXME: need caching allocators
+
+/**
+ * SECTION:gclosure
+ * @short_description: Functions as first-class objects
+ * @title: Closures
+ *
+ * A #GClosure represents a callback supplied by the programmer. It
+ * will generally comprise a function of some kind and a marshaller
+ * used to call it. It is the responsibility of the marshaller to
+ * convert the arguments for the invocation from #GValues into
+ * a suitable form, perform the callback on the converted arguments,
+ * and transform the return value back into a #GValue.
+ *
+ * In the case of C programs, a closure usually just holds a pointer
+ * to a function and maybe a data argument, and the marshaller
+ * converts between #GValue and native C types. The GObject
+ * library provides the #GCClosure type for this purpose. Bindings for
+ * other languages need marshallers which convert between #GValue<!--
+ * -->s and suitable representations in the runtime of the language in
+ * order to use functions written in that languages as callbacks.
+ *
+ * Within GObject, closures play an important role in the
+ * implementation of signals. When a signal is registered, the
+ * @c_marshaller argument to g_signal_new() specifies the default C
+ * marshaller for any closure which is connected to this
+ * signal. GObject provides a number of C marshallers for this
+ * purpose, see the g_cclosure_marshal_*() functions. Additional C
+ * marshallers can be generated with the [glib-genmarshal][glib-genmarshal]
+ * utility.  Closures can be explicitly connected to signals with
+ * g_signal_connect_closure(), but it usually more convenient to let
+ * GObject create a closure automatically by using one of the
+ * g_signal_connect_*() functions which take a callback function/user
+ * data pair.
+ *
+ * Using closures has a number of important advantages over a simple
+ * callback function/data pointer combination:
+ * 
+ * - Closures allow the callee to get the types of the callback parameters,
+ *   which means that language bindings don't have to write individual glue
+ *   for each callback type.
+ *
+ * - The reference counting of #GClosure makes it easy to handle reentrancy
+ *   right; if a callback is removed while it is being invoked, the closure
+ *   and its parameters won't be freed until the invocation finishes.
+ *
+ * - g_closure_invalidate() and invalidation notifiers allow callbacks to be
+ *   automatically removed when the objects they point to go away.
  */
 
 #define        CLOSURE_MAX_REF_COUNT           ((1 << 15) - 1)
 #define        CLOSURE_MAX_N_GUARDS            ((1 << 1) - 1)
 #define        CLOSURE_MAX_N_FNOTIFIERS        ((1 << 2) - 1)
 #define        CLOSURE_MAX_N_INOTIFIERS        ((1 << 8) - 1)
-#define        CLOSURE_N_MFUNCS(cl)            ((cl)->meta_marshal + \
-                                         ((cl)->n_guards << 1L))
+#define        CLOSURE_N_MFUNCS(cl)            (((cl)->n_guards << 1L))
+/* same as G_CLOSURE_N_NOTIFIERS() (keep in sync) */
 #define        CLOSURE_N_NOTIFIERS(cl)         (CLOSURE_N_MFUNCS (cl) + \
                                          (cl)->n_fnotifiers + \
                                          (cl)->n_inotifiers)
+
+typedef union {
+  GClosure closure;
+  volatile gint vint;
+} ClosureInt;
+
+#define CHANGE_FIELD(_closure, _field, _OP, _value, _must_set, _SET_OLD, _SET_NEW)      \
+G_STMT_START {                                                                          \
+  ClosureInt *cunion = (ClosureInt*) _closure;                                                 \
+  gint new_int, old_int, success;                                                              \
+  do                                                                                   \
+    {                                                                                  \
+      ClosureInt tmp;                                                                  \
+      tmp.vint = old_int = cunion->vint;                                               \
+      _SET_OLD tmp.closure._field;                                                      \
+      tmp.closure._field _OP _value;                                                   \
+      _SET_NEW tmp.closure._field;                                                      \
+      new_int = tmp.vint;                                                              \
+      success = g_atomic_int_compare_and_exchange (&cunion->vint, old_int, new_int);    \
+    }                                                                                  \
+  while (!success && _must_set);                                                        \
+} G_STMT_END
+
+#define SWAP(_closure, _field, _value, _oldv)   CHANGE_FIELD (_closure, _field, =, _value, TRUE, *(_oldv) =,     (void) )
+#define SET(_closure, _field, _value)           CHANGE_FIELD (_closure, _field, =, _value, TRUE,     (void),     (void) )
+#define INC(_closure, _field)                   CHANGE_FIELD (_closure, _field, +=,     1, TRUE,     (void),     (void) )
+#define INC_ASSIGN(_closure, _field, _newv)     CHANGE_FIELD (_closure, _field, +=,     1, TRUE,     (void), *(_newv) = )
+#define DEC(_closure, _field)                   CHANGE_FIELD (_closure, _field, -=,     1, TRUE,     (void),     (void) )
+#define DEC_ASSIGN(_closure, _field, _newv)     CHANGE_FIELD (_closure, _field, -=,     1, TRUE,     (void), *(_newv) = )
+
+#if 0   /* for non-thread-safe closures */
+#define SWAP(cl,f,v,o)     (void) (*(o) = cl->f, cl->f = v)
+#define SET(cl,f,v)        (void) (cl->f = v)
+#define INC(cl,f)          (void) (cl->f += 1)
+#define INC_ASSIGN(cl,f,n) (void) (cl->f += 1, *(n) = cl->f)
+#define DEC(cl,f)          (void) (cl->f -= 1)
+#define DEC_ASSIGN(cl,f,n) (void) (cl->f -= 1, *(n) = cl->f)
+#endif
+
 enum {
   FNOTIFY,
   INOTIFY,
@@ -44,29 +140,66 @@ enum {
 
 
 /* --- functions --- */
+/**
+ * g_closure_new_simple:
+ * @sizeof_closure: the size of the structure to allocate, must be at least
+ *                  `sizeof (GClosure)`
+ * @data: data to store in the @data field of the newly allocated #GClosure
+ *
+ * Allocates a struct of the given size and initializes the initial
+ * part as a #GClosure. This function is mainly useful when
+ * implementing new types of closures.
+ *
+ * |[<!-- language="C" --> 
+ * typedef struct _MyClosure MyClosure;
+ * struct _MyClosure
+ * {
+ *   GClosure closure;
+ *   // extra data goes here
+ * };
+ *
+ * static void
+ * my_closure_finalize (gpointer  notify_data,
+ *                      GClosure *closure)
+ * {
+ *   MyClosure *my_closure = (MyClosure *)closure;
+ *
+ *   // free extra data here
+ * }
+ *
+ * MyClosure *my_closure_new (gpointer data)
+ * {
+ *   GClosure *closure;
+ *   MyClosure *my_closure;
+ *
+ *   closure = g_closure_new_simple (sizeof (MyClosure), data);
+ *   my_closure = (MyClosure *) closure;
+ *
+ *   // initialize extra data here
+ *
+ *   g_closure_add_finalize_notifier (closure, notify_data,
+ *                                    my_closure_finalize);
+ *   return my_closure;
+ * }
+ * ]|
+ *
+ * Returns: (transfer full): a newly allocated #GClosure
+ */
 GClosure*
 g_closure_new_simple (guint           sizeof_closure,
                      gpointer        data)
 {
+  GRealClosure *real_closure;
   GClosure *closure;
 
   g_return_val_if_fail (sizeof_closure >= sizeof (GClosure), NULL);
+  sizeof_closure = sizeof_closure + sizeof (GRealClosure) - sizeof (GClosure);
 
-  closure = g_malloc (sizeof_closure);
-  closure->ref_count = 1;
-  closure->meta_marshal = 0;
-  closure->n_guards = 0;
-  closure->n_fnotifiers = 0;
-  closure->n_inotifiers = 0;
-  closure->in_inotify = FALSE;
-  closure->floating = TRUE;
-  closure->derivative_flag = 0;
-  closure->in_marshal = FALSE;
-  closure->is_invalid = FALSE;
-  closure->marshal = NULL;
+  real_closure = g_malloc0 (sizeof_closure);
+  closure = &real_closure->closure;
+  SET (closure, ref_count, 1);
+  SET (closure, floating, TRUE);
   closure->data = data;
-  closure->notifiers = NULL;
-  memset (G_STRUCT_MEMBER_P (closure, sizeof (*closure)), 0, sizeof_closure - sizeof (*closure));
 
   return closure;
 }
@@ -76,20 +209,19 @@ closure_invoke_notifiers (GClosure *closure,
                          guint     notify_type)
 {
   /* notifier layout:
-   *     meta_marshal  n_guards    n_guards     n_fnotif.  n_inotifiers
-   * ->[[meta_marshal][pre_guards][post_guards][fnotifers][inotifiers]]
+   *     n_guards    n_guards     n_fnotif.  n_inotifiers
+   * ->[[pre_guards][post_guards][fnotifiers][inotifiers]]
    *
-   * CLOSURE_N_MFUNCS(cl)    = meta_marshal + n_guards + n_guards;
+   * CLOSURE_N_MFUNCS(cl)    = n_guards + n_guards;
    * CLOSURE_N_NOTIFIERS(cl) = CLOSURE_N_MFUNCS(cl) + n_fnotifiers + n_inotifiers
    *
    * constrains/catches:
    * - closure->notifiers may be reloacted during callback
    * - closure->n_fnotifiers and closure->n_inotifiers may change during callback
    * - i.e. callbacks can be removed/added during invocation
-   * - have to prepare for callback removal during invocation (->marshal & ->data)
-   * - have to distinguish (->marshal & ->data) for INOTIFY/FNOTIFY (->in_inotify)
+   * - must prepare for callback removal during FNOTIFY and INOTIFY (done via ->marshal= & ->data=)
+   * - must distinguish (->marshal= & ->data=) for INOTIFY vs. FNOTIFY (via ->in_inotify)
    * + closure->n_guards is const during PRE_NOTIFY & POST_NOTIFY
-   * + closure->meta_marshal is const for all cases
    * + none of the callbacks can cause recursion
    * + closure->n_inotifiers is const 0 during FNOTIFY
    */
@@ -100,10 +232,11 @@ closure_invoke_notifiers (GClosure *closure,
     case FNOTIFY:
       while (closure->n_fnotifiers)
        {
-         register guint n = --closure->n_fnotifiers;
+          guint n;
+         DEC_ASSIGN (closure, n_fnotifiers, &n);
 
          ndata = closure->notifiers + CLOSURE_N_MFUNCS (closure) + n;
-         closure->marshal = (gpointer) ndata->notify;
+         closure->marshal = (GClosureMarshal) ndata->notify;
          closure->data = ndata->data;
          ndata->notify (ndata->data, closure);
        }
@@ -111,23 +244,24 @@ closure_invoke_notifiers (GClosure *closure,
       closure->data = NULL;
       break;
     case INOTIFY:
-      closure->in_inotify = TRUE;
+      SET (closure, in_inotify, TRUE);
       while (closure->n_inotifiers)
        {
-          register guint n = --closure->n_inotifiers;
+          guint n;
+          DEC_ASSIGN (closure, n_inotifiers, &n);
 
          ndata = closure->notifiers + CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers + n;
-         closure->marshal = (gpointer) ndata->notify;
+         closure->marshal = (GClosureMarshal) ndata->notify;
          closure->data = ndata->data;
          ndata->notify (ndata->data, closure);
        }
       closure->marshal = NULL;
       closure->data = NULL;
-      closure->in_inotify = FALSE;
+      SET (closure, in_inotify, FALSE);
       break;
     case PRE_NOTIFY:
       i = closure->n_guards;
-      offs = closure->meta_marshal;
+      offs = 0;
       while (i--)
        {
          ndata = closure->notifiers + offs + i;
@@ -136,7 +270,7 @@ closure_invoke_notifiers (GClosure *closure,
       break;
     case POST_NOTIFY:
       i = closure->n_guards;
-      offs = closure->meta_marshal + i;
+      offs = i;
       while (i--)
        {
          ndata = closure->notifiers + offs + i;
@@ -146,36 +280,78 @@ closure_invoke_notifiers (GClosure *closure,
     }
 }
 
+static void
+g_closure_set_meta_va_marshal (GClosure       *closure,
+                              GVaClosureMarshal va_meta_marshal)
+{
+  GRealClosure *real_closure;
+
+  g_return_if_fail (closure != NULL);
+  g_return_if_fail (va_meta_marshal != NULL);
+  g_return_if_fail (closure->is_invalid == FALSE);
+  g_return_if_fail (closure->in_marshal == FALSE);
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  g_return_if_fail (real_closure->meta_marshal != NULL);
+
+  real_closure->va_meta_marshal = va_meta_marshal;
+}
+
+/**
+ * g_closure_set_meta_marshal: (skip)
+ * @closure: a #GClosure
+ * @marshal_data: context-dependent data to pass to @meta_marshal
+ * @meta_marshal: a #GClosureMarshal function
+ *
+ * Sets the meta marshaller of @closure.  A meta marshaller wraps
+ * @closure->marshal and modifies the way it is called in some
+ * fashion. The most common use of this facility is for C callbacks.
+ * The same marshallers (generated by [glib-genmarshal][glib-genmarshal]),
+ * are used everywhere, but the way that we get the callback function
+ * differs. In most cases we want to use @closure->callback, but in
+ * other cases we want to use some different technique to retrieve the
+ * callback function.
+ *
+ * For example, class closures for signals (see
+ * g_signal_type_cclosure_new()) retrieve the callback function from a
+ * fixed offset in the class structure.  The meta marshaller retrieves
+ * the right callback and passes it to the marshaller as the
+ * @marshal_data argument.
+ */
 void
 g_closure_set_meta_marshal (GClosure       *closure,
                            gpointer        marshal_data,
                            GClosureMarshal meta_marshal)
 {
-  GClosureNotifyData *notifiers;
-  guint n;
+  GRealClosure *real_closure;
 
   g_return_if_fail (closure != NULL);
   g_return_if_fail (meta_marshal != NULL);
   g_return_if_fail (closure->is_invalid == FALSE);
   g_return_if_fail (closure->in_marshal == FALSE);
-  g_return_if_fail (closure->meta_marshal == 0);
 
-  n = CLOSURE_N_NOTIFIERS (closure);
-  notifiers = closure->notifiers;
-  closure->notifiers = g_renew (GClosureNotifyData, NULL, CLOSURE_N_NOTIFIERS (closure) + 1);
-  if (notifiers)
-    {
-      /* usually the meta marshal will be setup right after creation, so the
-       * g_memmove() should be rare-case scenario
-       */
-      g_memmove (closure->notifiers + 1, notifiers, CLOSURE_N_NOTIFIERS (closure) * sizeof (notifiers[0]));
-      g_free (notifiers);
-    }
-  closure->notifiers[0].data = marshal_data;
-  closure->notifiers[0].notify = (GClosureNotify) meta_marshal;
-  closure->meta_marshal = 1;
+  real_closure = G_REAL_CLOSURE (closure);
+
+  g_return_if_fail (real_closure->meta_marshal == NULL);
+
+  real_closure->meta_marshal = meta_marshal;
+  real_closure->meta_marshal_data = marshal_data;
 }
 
+/**
+ * g_closure_add_marshal_guards: (skip)
+ * @closure: a #GClosure
+ * @pre_marshal_data: data to pass to @pre_marshal_notify
+ * @pre_marshal_notify: a function to call before the closure callback
+ * @post_marshal_data: data to pass to @post_marshal_notify
+ * @post_marshal_notify: a function to call after the closure callback
+ *
+ * Adds a pair of notifiers which get invoked before and after the
+ * closure callback, respectively. This is typically used to protect
+ * the extra arguments for the duration of the callback. See
+ * g_object_watch_closure() for an example of marshal guards.
+ */
 void
 g_closure_add_marshal_guards (GClosure      *closure,
                              gpointer       pre_marshal_data,
@@ -210,20 +386,33 @@ g_closure_add_marshal_guards (GClosure      *closure,
     closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
                        closure->n_fnotifiers)] = closure->notifiers[CLOSURE_N_MFUNCS (closure) + 1];
   if (closure->n_guards)
-    closure->notifiers[(closure->meta_marshal +
-                       closure->n_guards +
-                       closure->n_guards + 1)] = closure->notifiers[closure->meta_marshal + closure->n_guards];
-  i = closure->n_guards++;
-  closure->notifiers[closure->meta_marshal + i].data = pre_marshal_data;
-  closure->notifiers[closure->meta_marshal + i].notify = pre_marshal_notify;
-  closure->notifiers[closure->meta_marshal + i + 1].data = post_marshal_data;
-  closure->notifiers[closure->meta_marshal + i + 1].notify = post_marshal_notify;
+    closure->notifiers[(closure->n_guards +
+                       closure->n_guards + 1)] = closure->notifiers[closure->n_guards];
+  i = closure->n_guards;
+  closure->notifiers[i].data = pre_marshal_data;
+  closure->notifiers[i].notify = pre_marshal_notify;
+  closure->notifiers[i + 1].data = post_marshal_data;
+  closure->notifiers[i + 1].notify = post_marshal_notify;
+  INC (closure, n_guards);
 }
 
+/**
+ * g_closure_add_finalize_notifier: (skip)
+ * @closure: a #GClosure
+ * @notify_data: data to pass to @notify_func
+ * @notify_func: the callback function to register
+ *
+ * Registers a finalization notifier which will be called when the
+ * reference count of @closure goes down to 0. Multiple finalization
+ * notifiers on a single closure are invoked in unspecified order. If
+ * a single call to g_closure_unref() results in the closure being
+ * both invalidated and finalized, then the invalidate notifiers will
+ * be run before the finalize notifiers.
+ */
 void
-g_closure_add_fnotify (GClosure      *closure,
-                      gpointer       notify_data,
-                      GClosureNotify notify_func)
+g_closure_add_finalize_notifier (GClosure      *closure,
+                                gpointer       notify_data,
+                                GClosureNotify notify_func)
 {
   guint i;
 
@@ -237,15 +426,27 @@ g_closure_add_fnotify (GClosure      *closure,
                        closure->n_fnotifiers +
                        closure->n_inotifiers)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
                                                                      closure->n_fnotifiers + 0)];
-  i = CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers++;
+  i = CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers;
   closure->notifiers[i].data = notify_data;
   closure->notifiers[i].notify = notify_func;
+  INC (closure, n_fnotifiers);
 }
 
+/**
+ * g_closure_add_invalidate_notifier: (skip)
+ * @closure: a #GClosure
+ * @notify_data: data to pass to @notify_func
+ * @notify_func: the callback function to register
+ *
+ * Registers an invalidation notifier which will be called when the
+ * @closure is invalidated with g_closure_invalidate(). Invalidation
+ * notifiers are invoked before finalization notifiers, in an
+ * unspecified order.
+ */
 void
-g_closure_add_inotify (GClosure      *closure,
-                      gpointer       notify_data,
-                      GClosureNotify notify_func)
+g_closure_add_invalidate_notifier (GClosure      *closure,
+                                  gpointer       notify_data,
+                                  GClosureNotify notify_func)
 {
   guint i;
 
@@ -255,9 +456,10 @@ g_closure_add_inotify (GClosure      *closure,
   g_return_if_fail (closure->n_inotifiers < CLOSURE_MAX_N_INOTIFIERS);
 
   closure->notifiers = g_renew (GClosureNotifyData, closure->notifiers, CLOSURE_N_NOTIFIERS (closure) + 1);
-  i = CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers + closure->n_inotifiers++;
+  i = CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers + closure->n_inotifiers;
   closure->notifiers[i].data = notify_data;
   closure->notifiers[i].notify = notify_func;
+  INC (closure, n_inotifiers);
 }
 
 static inline gboolean
@@ -271,7 +473,7 @@ closure_try_remove_inotify (GClosure       *closure,
   for (ndata = nlast + 1 - closure->n_inotifiers; ndata <= nlast; ndata++)
     if (ndata->notify == notify_func && ndata->data == notify_data)
       {
-       closure->n_inotifiers -= 1;
+       DEC (closure, n_inotifiers);
        if (ndata < nlast)
          *ndata = *nlast;
 
@@ -291,7 +493,7 @@ closure_try_remove_fnotify (GClosure       *closure,
   for (ndata = nlast + 1 - closure->n_fnotifiers; ndata <= nlast; ndata++)
     if (ndata->notify == notify_func && ndata->data == notify_data)
       {
-       closure->n_fnotifiers -= 1;
+       DEC (closure, n_fnotifiers);
        if (ndata < nlast)
          *ndata = *nlast;
        if (closure->n_inotifiers)
@@ -304,18 +506,47 @@ closure_try_remove_fnotify (GClosure       *closure,
   return FALSE;
 }
 
+/**
+ * g_closure_ref:
+ * @closure: #GClosure to increment the reference count on
+ *
+ * Increments the reference count on a closure to force it staying
+ * alive while the caller holds a pointer to it.
+ *
+ * Returns: (transfer none): The @closure passed in, for convenience
+ */
 GClosure*
 g_closure_ref (GClosure *closure)
 {
+  guint new_ref_count;
   g_return_val_if_fail (closure != NULL, NULL);
   g_return_val_if_fail (closure->ref_count > 0, NULL);
   g_return_val_if_fail (closure->ref_count < CLOSURE_MAX_REF_COUNT, NULL);
 
-  closure->ref_count += 1;
+  INC_ASSIGN (closure, ref_count, &new_ref_count);
+  g_return_val_if_fail (new_ref_count > 1, NULL);
 
   return closure;
 }
 
+/**
+ * g_closure_invalidate:
+ * @closure: GClosure to invalidate
+ *
+ * Sets a flag on the closure to indicate that its calling
+ * environment has become invalid, and thus causes any future
+ * invocations of g_closure_invoke() on this @closure to be
+ * ignored. Also, invalidation notifiers installed on the closure will
+ * be called at this point. Note that unless you are holding a
+ * reference to the closure yourself, the invalidation notifiers may
+ * unref the closure and cause it to be destroyed, so if you need to
+ * access the closure after calling g_closure_invalidate(), make sure
+ * that you've previously called g_closure_ref().
+ *
+ * Note that g_closure_invalidate() will also be called when the
+ * reference count of a closure drops to zero (unless it has already
+ * been invalidated before).
+ */
 void
 g_closure_invalidate (GClosure *closure)
 {
@@ -323,32 +554,91 @@ g_closure_invalidate (GClosure *closure)
 
   if (!closure->is_invalid)
     {
-      closure->ref_count += 1; /* preserve floating flag */
-      closure->is_invalid = TRUE;
-      closure_invoke_notifiers (closure, INOTIFY);
+      gboolean was_invalid;
+      g_closure_ref (closure);           /* preserve floating flag */
+      SWAP (closure, is_invalid, TRUE, &was_invalid);
+      /* invalidate only once */
+      if (!was_invalid)
+        closure_invoke_notifiers (closure, INOTIFY);
       g_closure_unref (closure);
     }
 }
 
+/**
+ * g_closure_unref:
+ * @closure: #GClosure to decrement the reference count on
+ *
+ * Decrements the reference count of a closure after it was previously
+ * incremented by the same caller. If no other callers are using the
+ * closure, then the closure will be destroyed and freed.
+ */
 void
 g_closure_unref (GClosure *closure)
 {
+  guint new_ref_count;
+
   g_return_if_fail (closure != NULL);
   g_return_if_fail (closure->ref_count > 0);
 
   if (closure->ref_count == 1) /* last unref, invalidate first */
     g_closure_invalidate (closure);
 
-  closure->ref_count -= 1;
+  DEC_ASSIGN (closure, ref_count, &new_ref_count);
 
-  if (closure->ref_count == 0)
+  if (new_ref_count == 0)
     {
       closure_invoke_notifiers (closure, FNOTIFY);
       g_free (closure->notifiers);
-      g_free (closure);
+      g_free (G_REAL_CLOSURE (closure));
     }
 }
 
+/**
+ * g_closure_sink:
+ * @closure: #GClosure to decrement the initial reference count on, if it's
+ *           still being held
+ *
+ * Takes over the initial ownership of a closure.  Each closure is
+ * initially created in a "floating" state, which means that the initial
+ * reference count is not owned by any caller. g_closure_sink() checks
+ * to see if the object is still floating, and if so, unsets the
+ * floating state and decreases the reference count. If the closure
+ * is not floating, g_closure_sink() does nothing. The reason for the
+ * existence of the floating state is to prevent cumbersome code
+ * sequences like:
+ * |[<!-- language="C" --> 
+ * closure = g_cclosure_new (cb_func, cb_data);
+ * g_source_set_closure (source, closure);
+ * g_closure_unref (closure); // GObject doesn't really need this
+ * ]|
+ * Because g_source_set_closure() (and similar functions) take ownership of the
+ * initial reference count, if it is unowned, we instead can write:
+ * |[<!-- language="C" --> 
+ * g_source_set_closure (source, g_cclosure_new (cb_func, cb_data));
+ * ]|
+ *
+ * Generally, this function is used together with g_closure_ref(). Ane example
+ * of storing a closure for later notification looks like:
+ * |[<!-- language="C" --> 
+ * static GClosure *notify_closure = NULL;
+ * void
+ * foo_notify_set_closure (GClosure *closure)
+ * {
+ *   if (notify_closure)
+ *     g_closure_unref (notify_closure);
+ *   notify_closure = closure;
+ *   if (notify_closure)
+ *     {
+ *       g_closure_ref (notify_closure);
+ *       g_closure_sink (notify_closure);
+ *     }
+ * }
+ * ]|
+ *
+ * Because g_closure_sink() may decrement the reference count of a closure
+ * (if it hasn't been called on @closure yet) just like g_closure_unref(),
+ * g_closure_ref() should be called prior to this function.
+ */
 void
 g_closure_sink (GClosure *closure)
 {
@@ -356,52 +646,90 @@ g_closure_sink (GClosure *closure)
   g_return_if_fail (closure->ref_count > 0);
 
   /* floating is basically a kludge to avoid creating closures
-   * with a ref_count of 0. so the intial ref_count a closure has
+   * with a ref_count of 0. so the initial ref_count a closure has
    * is unowned. with invoking g_closure_sink() code may
    * indicate that it takes over that intiial ref_count.
    */
   if (closure->floating)
     {
-      closure->floating = FALSE;
-      if (closure->ref_count > 1)
-       closure->ref_count -= 1;
-      else
-       g_closure_unref (closure);
+      gboolean was_floating;
+      SWAP (closure, floating, FALSE, &was_floating);
+      /* unref floating flag only once */
+      if (was_floating)
+        g_closure_unref (closure);
     }
 }
 
+/**
+ * g_closure_remove_invalidate_notifier: (skip)
+ * @closure: a #GClosure
+ * @notify_data: data which was passed to g_closure_add_invalidate_notifier()
+ *               when registering @notify_func
+ * @notify_func: the callback function to remove
+ *
+ * Removes an invalidation notifier.
+ *
+ * Notice that notifiers are automatically removed after they are run.
+ */
 void
-g_closure_remove_inotify (GClosure      *closure,
-                         gpointer       notify_data,
-                         GClosureNotify notify_func)
+g_closure_remove_invalidate_notifier (GClosure      *closure,
+                                     gpointer       notify_data,
+                                     GClosureNotify notify_func)
 {
   g_return_if_fail (closure != NULL);
   g_return_if_fail (notify_func != NULL);
 
-  if (closure->is_invalid && closure->in_inotify && /* account removal of notify_func() while its called */
-      ((gpointer) closure->marshal) == ((gpointer) notify_func) && closure->data == notify_data)
+  if (closure->is_invalid && closure->in_inotify && /* account removal of notify_func() while it's called */
+      ((gpointer) closure->marshal) == ((gpointer) notify_func) &&
+      closure->data == notify_data)
     closure->marshal = NULL;
   else if (!closure_try_remove_inotify (closure, notify_data, notify_func))
     g_warning (G_STRLOC ": unable to remove uninstalled invalidation notifier: %p (%p)",
               notify_func, notify_data);
 }
 
+/**
+ * g_closure_remove_finalize_notifier: (skip)
+ * @closure: a #GClosure
+ * @notify_data: data which was passed to g_closure_add_finalize_notifier()
+ *  when registering @notify_func
+ * @notify_func: the callback function to remove
+ *
+ * Removes a finalization notifier.
+ *
+ * Notice that notifiers are automatically removed after they are run.
+ */
 void
-g_closure_remove_fnotify (GClosure      *closure,
-                          gpointer       notify_data,
-                         GClosureNotify notify_func)
+g_closure_remove_finalize_notifier (GClosure      *closure,
+                                   gpointer       notify_data,
+                                   GClosureNotify notify_func)
 {
   g_return_if_fail (closure != NULL);
   g_return_if_fail (notify_func != NULL);
 
-  if (closure->is_invalid && !closure->in_inotify && /* account removal of notify_func() while its called */
-      ((gpointer) closure->marshal) == ((gpointer) notify_func) && closure->data == notify_data)
+  if (closure->is_invalid && !closure->in_inotify && /* account removal of notify_func() while it's called */
+      ((gpointer) closure->marshal) == ((gpointer) notify_func) &&
+      closure->data == notify_data)
     closure->marshal = NULL;
   else if (!closure_try_remove_fnotify (closure, notify_data, notify_func))
     g_warning (G_STRLOC ": unable to remove uninstalled finalization notifier: %p (%p)",
                notify_func, notify_data);
 }
 
+/**
+ * g_closure_invoke:
+ * @closure: a #GClosure
+ * @return_value: (allow-none): a #GValue to store the return
+ *                value. May be %NULL if the callback of @closure
+ *                doesn't return a value.
+ * @n_param_values: the length of the @param_values array
+ * @param_values: (array length=n_param_values): an array of
+ *                #GValues holding the arguments on which to
+ *                invoke the callback of @closure
+ * @invocation_hint: (allow-none): a context-dependent invocation hint
+ *
+ * Invokes the closure, i.e. executes the callback represented by the @closure.
+ */
 void
 g_closure_invoke (GClosure       *closure,
                  GValue /*out*/ *return_value,
@@ -409,21 +737,26 @@ g_closure_invoke (GClosure       *closure,
                  const GValue   *param_values,
                  gpointer        invocation_hint)
 {
+  GRealClosure *real_closure;
+
   g_return_if_fail (closure != NULL);
-  g_return_if_fail (closure->marshal || closure->meta_marshal);
 
+  real_closure = G_REAL_CLOSURE (closure);
+
+  g_closure_ref (closure);      /* preserve floating flag */
   if (!closure->is_invalid)
     {
       GClosureMarshal marshal;
       gpointer marshal_data;
       gboolean in_marshal = closure->in_marshal;
 
-      closure->ref_count += 1; /* preserve floating flag */
-      closure->in_marshal = TRUE;
-      if (closure->meta_marshal)
+      g_return_if_fail (closure->marshal || real_closure->meta_marshal);
+
+      SET (closure, in_marshal, TRUE);
+      if (real_closure->meta_marshal)
        {
-         marshal_data = closure->notifiers[0].data;
-         marshal = (GClosureMarshal) closure->notifiers[0].notify;
+         marshal_data = real_closure->meta_marshal_data;
+         marshal = real_closure->meta_marshal;
        }
       else
        {
@@ -439,12 +772,88 @@ g_closure_invoke (GClosure       *closure,
               marshal_data);
       if (!in_marshal)
        closure_invoke_notifiers (closure, POST_NOTIFY);
-      closure->in_marshal = in_marshal;
-      g_closure_unref (closure);
+      SET (closure, in_marshal, in_marshal);
     }
+  g_closure_unref (closure);
+}
+
+gboolean
+_g_closure_supports_invoke_va (GClosure       *closure)
+{
+  GRealClosure *real_closure;
+
+  g_return_val_if_fail (closure != NULL, FALSE);
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  return
+    real_closure->va_marshal != NULL &&
+    (real_closure->meta_marshal == NULL ||
+     real_closure->va_meta_marshal != NULL);
 }
 
 void
+_g_closure_invoke_va (GClosure       *closure,
+                     GValue /*out*/ *return_value,
+                     gpointer        instance,
+                     va_list         args,
+                     int             n_params,
+                     GType          *param_types)
+{
+  GRealClosure *real_closure;
+
+  g_return_if_fail (closure != NULL);
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  g_closure_ref (closure);      /* preserve floating flag */
+  if (!closure->is_invalid)
+    {
+      GVaClosureMarshal marshal;
+      gpointer marshal_data;
+      gboolean in_marshal = closure->in_marshal;
+
+      g_return_if_fail (closure->marshal || real_closure->meta_marshal);
+
+      SET (closure, in_marshal, TRUE);
+      if (real_closure->va_meta_marshal)
+       {
+         marshal_data = real_closure->meta_marshal_data;
+         marshal = real_closure->va_meta_marshal;
+       }
+      else
+       {
+         marshal_data = NULL;
+         marshal = real_closure->va_marshal;
+       }
+      if (!in_marshal)
+       closure_invoke_notifiers (closure, PRE_NOTIFY);
+      marshal (closure,
+              return_value,
+              instance, args,
+              marshal_data,
+              n_params, param_types);
+      if (!in_marshal)
+       closure_invoke_notifiers (closure, POST_NOTIFY);
+      SET (closure, in_marshal, in_marshal);
+    }
+  g_closure_unref (closure);
+}
+
+
+/**
+ * g_closure_set_marshal: (skip)
+ * @closure: a #GClosure
+ * @marshal: a #GClosureMarshal function
+ *
+ * Sets the marshaller of @closure. The `marshal_data`
+ * of @marshal provides a way for a meta marshaller to provide additional
+ * information to the marshaller. (See g_closure_set_meta_marshal().) For
+ * GObject's C predefined marshallers (the g_cclosure_marshal_*()
+ * functions), what it provides is a callback function to use instead of
+ * @closure->callback.
+ */
+void
 g_closure_set_marshal (GClosure       *closure,
                       GClosureMarshal marshal)
 {
@@ -458,6 +867,35 @@ g_closure_set_marshal (GClosure       *closure,
     closure->marshal = marshal;
 }
 
+void
+_g_closure_set_va_marshal (GClosure       *closure,
+                          GVaClosureMarshal marshal)
+{
+  GRealClosure *real_closure;
+
+  g_return_if_fail (closure != NULL);
+  g_return_if_fail (marshal != NULL);
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  if (real_closure->va_marshal && real_closure->va_marshal != marshal)
+    g_warning ("attempt to override closure->va_marshal (%p) with new marshal (%p)",
+              real_closure->va_marshal, marshal);
+  else
+    real_closure->va_marshal = marshal;
+}
+
+/**
+ * g_cclosure_new: (skip)
+ * @callback_func: the function to invoke
+ * @user_data: user data to pass to @callback_func
+ * @destroy_data: destroy notify to be called when @user_data is no longer used
+ *
+ * Creates a new closure which invokes @callback_func with @user_data as
+ * the last parameter.
+ *
+ * Returns: a new #GCClosure
+ */
 GClosure*
 g_cclosure_new (GCallback      callback_func,
                gpointer       user_data,
@@ -469,12 +907,23 @@ g_cclosure_new (GCallback      callback_func,
   
   closure = g_closure_new_simple (sizeof (GCClosure), user_data);
   if (destroy_data)
-    g_closure_add_fnotify (closure, user_data, destroy_data);
-  ((GCClosure*) closure)->callback = callback_func;
+    g_closure_add_finalize_notifier (closure, user_data, destroy_data);
+  ((GCClosure*) closure)->callback = (gpointer) callback_func;
   
   return closure;
 }
 
+/**
+ * g_cclosure_new_swap: (skip)
+ * @callback_func: the function to invoke
+ * @user_data: user data to pass to @callback_func
+ * @destroy_data: destroy notify to be called when @user_data is no longer used
+ *
+ * Creates a new closure which invokes @callback_func with @user_data as
+ * the first parameter.
+ *
+ * Returns: (transfer full): a new #GCClosure
+ */
 GClosure*
 g_cclosure_new_swap (GCallback      callback_func,
                     gpointer       user_data,
@@ -486,9 +935,9 @@ g_cclosure_new_swap (GCallback      callback_func,
   
   closure = g_closure_new_simple (sizeof (GCClosure), user_data);
   if (destroy_data)
-    g_closure_add_fnotify (closure, user_data, destroy_data);
-  ((GCClosure*) closure)->callback = callback_func;
-  closure->derivative_flag = TRUE;
+    g_closure_add_finalize_notifier (closure, user_data, destroy_data);
+  ((GCClosure*) closure)->callback = (gpointer) callback_func;
+  SET (closure, derivative_flag, TRUE);
   
   return closure;
 }
@@ -503,7 +952,7 @@ g_type_class_meta_marshal (GClosure       *closure,
 {
   GTypeClass *class;
   gpointer callback;
-  /* GType itype = GPOINTER_TO_UINT (closure->data); */
+  /* GType itype = (GType) closure->data; */
   guint offset = GPOINTER_TO_UINT (marshal_data);
   
   class = G_TYPE_INSTANCE_GET_CLASS (g_value_peek_pointer (param_values + 0), itype, GTypeClass);
@@ -517,6 +966,34 @@ g_type_class_meta_marshal (GClosure       *closure,
 }
 
 static void
+g_type_class_meta_marshalv (GClosure *closure,
+                           GValue   *return_value,
+                           gpointer  instance,
+                           va_list   args,
+                           gpointer  marshal_data,
+                           int       n_params,
+                           GType    *param_types)
+{
+  GRealClosure *real_closure;
+  GTypeClass *class;
+  gpointer callback;
+  /* GType itype = (GType) closure->data; */
+  guint offset = GPOINTER_TO_UINT (marshal_data);
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  class = G_TYPE_INSTANCE_GET_CLASS (instance, itype, GTypeClass);
+  callback = G_STRUCT_MEMBER (gpointer, class, offset);
+  if (callback)
+    real_closure->va_marshal (closure,
+                             return_value,
+                             instance, args,
+                             callback,
+                             n_params,
+                             param_types);
+}
+
+static void
 g_type_iface_meta_marshal (GClosure       *closure,
                           GValue /*out*/ *return_value,
                           guint           n_param_values,
@@ -526,7 +1003,7 @@ g_type_iface_meta_marshal (GClosure       *closure,
 {
   GTypeClass *class;
   gpointer callback;
-  GType itype = GPOINTER_TO_UINT (closure->data);
+  GType itype = (GType) closure->data;
   guint offset = GPOINTER_TO_UINT (marshal_data);
   
   class = G_TYPE_INSTANCE_GET_INTERFACE (g_value_peek_pointer (param_values + 0), itype, GTypeClass);
@@ -539,6 +1016,82 @@ g_type_iface_meta_marshal (GClosure       *closure,
                      callback);
 }
 
+gboolean
+_g_closure_is_void (GClosure *closure,
+                   gpointer instance)
+{
+  GRealClosure *real_closure;
+  GTypeClass *class;
+  gpointer callback;
+  GType itype;
+  guint offset;
+
+  if (closure->is_invalid)
+    return TRUE;
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  if (real_closure->meta_marshal == g_type_iface_meta_marshal)
+    {
+      itype = (GType) closure->data;
+      offset = GPOINTER_TO_UINT (real_closure->meta_marshal_data);
+
+      class = G_TYPE_INSTANCE_GET_INTERFACE (instance, itype, GTypeClass);
+      callback = G_STRUCT_MEMBER (gpointer, class, offset);
+      return callback == NULL;
+    }
+  else if (real_closure->meta_marshal == g_type_class_meta_marshal)
+    {
+      offset = GPOINTER_TO_UINT (real_closure->meta_marshal_data);
+
+      class = G_TYPE_INSTANCE_GET_CLASS (instance, itype, GTypeClass);
+      callback = G_STRUCT_MEMBER (gpointer, class, offset);
+      return callback == NULL;
+    }
+
+  return FALSE;
+}
+
+static void
+g_type_iface_meta_marshalv (GClosure *closure,
+                           GValue   *return_value,
+                           gpointer  instance,
+                           va_list   args,
+                           gpointer  marshal_data,
+                           int       n_params,
+                           GType    *param_types)
+{
+  GRealClosure *real_closure;
+  GTypeClass *class;
+  gpointer callback;
+  GType itype = (GType) closure->data;
+  guint offset = GPOINTER_TO_UINT (marshal_data);
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  class = G_TYPE_INSTANCE_GET_INTERFACE (instance, itype, GTypeClass);
+  callback = G_STRUCT_MEMBER (gpointer, class, offset);
+  if (callback)
+    real_closure->va_marshal (closure,
+                             return_value,
+                             instance, args,
+                             callback,
+                             n_params,
+                             param_types);
+}
+
+/**
+ * g_signal_type_cclosure_new:
+ * @itype: the #GType identifier of an interface or classed type
+ * @struct_offset: the offset of the member function of @itype's class
+ *  structure which is to be invoked by the new closure
+ *
+ * Creates a new closure which invokes the function found at the offset
+ * @struct_offset in the class structure of the interface or classed type
+ * identified by @itype.
+ *
+ * Returns: a new #GCClosure
+ */
 GClosure*
 g_signal_type_cclosure_new (GType    itype,
                            guint    struct_offset)
@@ -548,11 +1101,783 @@ g_signal_type_cclosure_new (GType    itype,
   g_return_val_if_fail (G_TYPE_IS_CLASSED (itype) || G_TYPE_IS_INTERFACE (itype), NULL);
   g_return_val_if_fail (struct_offset >= sizeof (GTypeClass), NULL);
   
-  closure = g_closure_new_simple (sizeof (GClosure), GUINT_TO_POINTER (itype));
+  closure = g_closure_new_simple (sizeof (GClosure), (gpointer) itype);
   if (G_TYPE_IS_INTERFACE (itype))
-    g_closure_set_meta_marshal (closure, GUINT_TO_POINTER (struct_offset), g_type_iface_meta_marshal);
+    {
+      g_closure_set_meta_marshal (closure, GUINT_TO_POINTER (struct_offset), g_type_iface_meta_marshal);
+      g_closure_set_meta_va_marshal (closure, g_type_iface_meta_marshalv);
+    }
   else
-    g_closure_set_meta_marshal (closure, GUINT_TO_POINTER (struct_offset), g_type_class_meta_marshal);
-  
+    {
+      g_closure_set_meta_marshal (closure, GUINT_TO_POINTER (struct_offset), g_type_class_meta_marshal);
+      g_closure_set_meta_va_marshal (closure, g_type_class_meta_marshalv);
+    }
   return closure;
 }
+
+#include <ffi.h>
+static ffi_type *
+value_to_ffi_type (const GValue *gvalue,
+                   gpointer *value,
+                   gint *enum_tmpval,
+                   gboolean *tmpval_used)
+{
+  ffi_type *rettype = NULL;
+  GType type = g_type_fundamental (G_VALUE_TYPE (gvalue));
+  g_assert (type != G_TYPE_INVALID);
+
+  if (enum_tmpval)
+    {
+      g_assert (tmpval_used != NULL);
+      *tmpval_used = FALSE;
+    }
+
+  switch (type)
+    {
+    case G_TYPE_BOOLEAN:
+    case G_TYPE_CHAR:
+    case G_TYPE_INT:
+      rettype = &ffi_type_sint;
+      *value = (gpointer)&(gvalue->data[0].v_int);
+      break;
+    case G_TYPE_ENUM:
+      /* enums are stored in v_long even though they are integers, which makes
+       * marshalling through libffi somewhat complicated.  They need to be
+       * marshalled as signed ints, but we need to use a temporary int sized
+       * value to pass to libffi otherwise it'll pull the wrong value on
+       * BE machines with 32-bit integers when treating v_long as 32-bit int.
+       */
+      g_assert (enum_tmpval != NULL);
+      rettype = &ffi_type_sint;
+      *enum_tmpval = g_value_get_enum (gvalue);
+      *value = enum_tmpval;
+      *tmpval_used = TRUE;
+      break;
+    case G_TYPE_UCHAR:
+    case G_TYPE_UINT:
+    case G_TYPE_FLAGS:
+      rettype = &ffi_type_uint;
+      *value = (gpointer)&(gvalue->data[0].v_uint);
+      break;
+    case G_TYPE_STRING:
+    case G_TYPE_OBJECT:
+    case G_TYPE_BOXED:
+    case G_TYPE_PARAM:
+    case G_TYPE_POINTER:
+    case G_TYPE_INTERFACE:
+    case G_TYPE_VARIANT:
+      rettype = &ffi_type_pointer;
+      *value = (gpointer)&(gvalue->data[0].v_pointer);
+      break;
+    case G_TYPE_FLOAT:
+      rettype = &ffi_type_float;
+      *value = (gpointer)&(gvalue->data[0].v_float);
+      break;
+    case G_TYPE_DOUBLE:
+      rettype = &ffi_type_double;
+      *value = (gpointer)&(gvalue->data[0].v_double);
+      break;
+    case G_TYPE_LONG:
+      rettype = &ffi_type_slong;
+      *value = (gpointer)&(gvalue->data[0].v_long);
+      break;
+    case G_TYPE_ULONG:
+      rettype = &ffi_type_ulong;
+      *value = (gpointer)&(gvalue->data[0].v_ulong);
+      break;
+    case G_TYPE_INT64:
+      rettype = &ffi_type_sint64;
+      *value = (gpointer)&(gvalue->data[0].v_int64);
+      break;
+    case G_TYPE_UINT64:
+      rettype = &ffi_type_uint64;
+      *value = (gpointer)&(gvalue->data[0].v_uint64);
+      break;
+    default:
+      rettype = &ffi_type_pointer;
+      *value = NULL;
+      g_warning ("value_to_ffi_type: Unsupported fundamental type: %s", g_type_name (type));
+      break;
+    }
+  return rettype;
+}
+
+static void
+value_from_ffi_type (GValue *gvalue, gpointer *value)
+{
+  ffi_arg *int_val = (ffi_arg*) value;
+
+  switch (g_type_fundamental (G_VALUE_TYPE (gvalue)))
+    {
+    case G_TYPE_INT:
+      g_value_set_int (gvalue, (gint) *int_val);
+      break;
+    case G_TYPE_FLOAT:
+      g_value_set_float (gvalue, *(gfloat*)value);
+      break;
+    case G_TYPE_DOUBLE:
+      g_value_set_double (gvalue, *(gdouble*)value);
+      break;
+    case G_TYPE_BOOLEAN:
+      g_value_set_boolean (gvalue, (gboolean) *int_val);
+      break;
+    case G_TYPE_STRING:
+      g_value_take_string (gvalue, *(gchar**)value);
+      break;
+    case G_TYPE_CHAR:
+      g_value_set_schar (gvalue, (gint8) *int_val);
+      break;
+    case G_TYPE_UCHAR:
+      g_value_set_uchar (gvalue, (guchar) *int_val);
+      break;
+    case G_TYPE_UINT:
+      g_value_set_uint (gvalue, (guint) *int_val);
+      break;
+    case G_TYPE_POINTER:
+      g_value_set_pointer (gvalue, *(gpointer*)value);
+      break;
+    case G_TYPE_LONG:
+      g_value_set_long (gvalue, (glong) *int_val);
+      break;
+    case G_TYPE_ULONG:
+      g_value_set_ulong (gvalue, (gulong) *int_val);
+      break;
+    case G_TYPE_INT64:
+      g_value_set_int64 (gvalue, (gint64) *int_val);
+      break;
+    case G_TYPE_UINT64:
+      g_value_set_uint64 (gvalue, (guint64) *int_val);
+      break;
+    case G_TYPE_BOXED:
+      g_value_take_boxed (gvalue, *(gpointer*)value);
+      break;
+    case G_TYPE_ENUM:
+      g_value_set_enum (gvalue, (gint) *int_val);
+      break;
+    case G_TYPE_FLAGS:
+      g_value_set_flags (gvalue, (guint) *int_val);
+      break;
+    case G_TYPE_PARAM:
+      g_value_take_param (gvalue, *(gpointer*)value);
+      break;
+    case G_TYPE_OBJECT:
+      g_value_take_object (gvalue, *(gpointer*)value);
+      break;
+    case G_TYPE_VARIANT:
+      g_value_take_variant (gvalue, *(gpointer*)value);
+      break;
+    default:
+      g_warning ("value_from_ffi_type: Unsupported fundamental type: %s",
+                g_type_name (g_type_fundamental (G_VALUE_TYPE (gvalue))));
+    }
+}
+
+typedef union {
+  gpointer _gpointer;
+  float _float;
+  double _double;
+  gint _gint;
+  guint _guint;
+  glong _glong;
+  gulong _gulong;
+  gint64 _gint64;
+  guint64 _guint64;
+} va_arg_storage;
+
+static ffi_type *
+va_to_ffi_type (GType gtype,
+               va_list *va,
+               va_arg_storage *storage)
+{
+  ffi_type *rettype = NULL;
+  GType type = g_type_fundamental (gtype);
+  g_assert (type != G_TYPE_INVALID);
+
+  switch (type)
+    {
+    case G_TYPE_BOOLEAN:
+    case G_TYPE_CHAR:
+    case G_TYPE_INT:
+    case G_TYPE_ENUM:
+      rettype = &ffi_type_sint;
+      storage->_gint = va_arg (*va, gint);
+      break;
+    case G_TYPE_UCHAR:
+    case G_TYPE_UINT:
+    case G_TYPE_FLAGS:
+      rettype = &ffi_type_uint;
+      storage->_guint = va_arg (*va, guint);
+      break;
+    case G_TYPE_STRING:
+    case G_TYPE_OBJECT:
+    case G_TYPE_BOXED:
+    case G_TYPE_PARAM:
+    case G_TYPE_POINTER:
+    case G_TYPE_INTERFACE:
+    case G_TYPE_VARIANT:
+      rettype = &ffi_type_pointer;
+      storage->_gpointer = va_arg (*va, gpointer);
+      break;
+    case G_TYPE_FLOAT:
+      /* Float args are passed as doubles in varargs */
+      rettype = &ffi_type_float;
+      storage->_float = (float)va_arg (*va, double);
+      break;
+    case G_TYPE_DOUBLE:
+      rettype = &ffi_type_double;
+      storage->_double = va_arg (*va, double);
+      break;
+    case G_TYPE_LONG:
+      rettype = &ffi_type_slong;
+      storage->_glong = va_arg (*va, glong);
+      break;
+    case G_TYPE_ULONG:
+      rettype = &ffi_type_ulong;
+      storage->_gulong = va_arg (*va, gulong);
+      break;
+    case G_TYPE_INT64:
+      rettype = &ffi_type_sint64;
+      storage->_gint64 = va_arg (*va, gint64);
+      break;
+    case G_TYPE_UINT64:
+      rettype = &ffi_type_uint64;
+      storage->_guint64 = va_arg (*va, guint64);
+      break;
+    default:
+      rettype = &ffi_type_pointer;
+      storage->_guint64  = 0;
+      g_warning ("va_to_ffi_type: Unsupported fundamental type: %s", g_type_name (type));
+      break;
+    }
+  return rettype;
+}
+
+/**
+ * g_cclosure_marshal_generic:
+ * @closure: A #GClosure.
+ * @return_gvalue: A #GValue to store the return value. May be %NULL
+ *   if the callback of closure doesn't return a value.
+ * @n_param_values: The length of the @param_values array.
+ * @param_values: An array of #GValues holding the arguments
+ *   on which to invoke the callback of closure.
+ * @invocation_hint: The invocation hint given as the last argument to
+ *   g_closure_invoke().
+ * @marshal_data: Additional data specified when registering the
+ *   marshaller, see g_closure_set_marshal() and
+ *   g_closure_set_meta_marshal()
+ *
+ * A generic marshaller function implemented via
+ * [libffi](http://sourceware.org/libffi/).
+ *
+ * Normally this function is not passed explicitly to g_signal_new(),
+ * but used automatically by GLib when specifying a %NULL marshaller.
+ *
+ * Since: 2.30
+ */
+void
+g_cclosure_marshal_generic (GClosure     *closure,
+                            GValue       *return_gvalue,
+                            guint         n_param_values,
+                            const GValue *param_values,
+                            gpointer      invocation_hint,
+                            gpointer      marshal_data)
+{
+  ffi_type *rtype;
+  void *rvalue;
+  int n_args;
+  ffi_type **atypes;
+  void **args;
+  int i;
+  ffi_cif cif;
+  GCClosure *cc = (GCClosure*) closure;
+  gint *enum_tmpval;
+  gboolean tmpval_used = FALSE;
+
+  enum_tmpval = g_alloca (sizeof (gint));
+  if (return_gvalue && G_VALUE_TYPE (return_gvalue))
+    {
+      rtype = value_to_ffi_type (return_gvalue, &rvalue, enum_tmpval, &tmpval_used);
+    }
+  else
+    {
+      rtype = &ffi_type_void;
+    }
+
+  rvalue = g_alloca (MAX (rtype->size, sizeof (ffi_arg)));
+
+  n_args = n_param_values + 1;
+  atypes = g_alloca (sizeof (ffi_type *) * n_args);
+  args =  g_alloca (sizeof (gpointer) * n_args);
+
+  if (tmpval_used)
+    enum_tmpval = g_alloca (sizeof (gint));
+
+  if (G_CCLOSURE_SWAP_DATA (closure))
+    {
+      atypes[n_args-1] = value_to_ffi_type (param_values + 0,
+                                            &args[n_args-1],
+                                            enum_tmpval,
+                                            &tmpval_used);
+      atypes[0] = &ffi_type_pointer;
+      args[0] = &closure->data;
+    }
+  else
+    {
+      atypes[0] = value_to_ffi_type (param_values + 0,
+                                     &args[0],
+                                     enum_tmpval,
+                                     &tmpval_used);
+      atypes[n_args-1] = &ffi_type_pointer;
+      args[n_args-1] = &closure->data;
+    }
+
+  for (i = 1; i < n_args - 1; i++)
+    {
+      if (tmpval_used)
+        enum_tmpval = g_alloca (sizeof (gint));
+
+      atypes[i] = value_to_ffi_type (param_values + i,
+                                     &args[i],
+                                     enum_tmpval,
+                                     &tmpval_used);
+    }
+
+  if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, n_args, rtype, atypes) != FFI_OK)
+    return;
+
+  ffi_call (&cif, marshal_data ? marshal_data : cc->callback, rvalue, args);
+
+  if (return_gvalue && G_VALUE_TYPE (return_gvalue))
+    value_from_ffi_type (return_gvalue, rvalue);
+}
+
+void
+g_cclosure_marshal_generic_va (GClosure *closure,
+                              GValue   *return_value,
+                              gpointer  instance,
+                              va_list   args_list,
+                              gpointer  marshal_data,
+                              int       n_params,
+                              GType    *param_types)
+{
+  ffi_type *rtype;
+  void *rvalue;
+  int n_args;
+  ffi_type **atypes;
+  void **args;
+  va_arg_storage *storage;
+  int i;
+  ffi_cif cif;
+  GCClosure *cc = (GCClosure*) closure;
+  gint *enum_tmpval;
+  gboolean tmpval_used = FALSE;
+  va_list args_copy;
+
+  enum_tmpval = g_alloca (sizeof (gint));
+  if (return_value && G_VALUE_TYPE (return_value))
+    {
+      rtype = value_to_ffi_type (return_value, &rvalue, enum_tmpval, &tmpval_used);
+    }
+  else
+    {
+      rtype = &ffi_type_void;
+    }
+
+  rvalue = g_alloca (MAX (rtype->size, sizeof (ffi_arg)));
+
+  n_args = n_params + 2;
+  atypes = g_alloca (sizeof (ffi_type *) * n_args);
+  args =  g_alloca (sizeof (gpointer) * n_args);
+  storage = g_alloca (sizeof (va_arg_storage) * n_params);
+
+  if (G_CCLOSURE_SWAP_DATA (closure))
+    {
+      atypes[n_args-1] = &ffi_type_pointer;
+      args[n_args-1] = &instance;
+      atypes[0] = &ffi_type_pointer;
+      args[0] = &closure->data;
+    }
+  else
+    {
+      atypes[0] = &ffi_type_pointer;
+      args[0] = &instance;
+      atypes[n_args-1] = &ffi_type_pointer;
+      args[n_args-1] = &closure->data;
+    }
+
+  G_VA_COPY (args_copy, args_list);
+
+  /* Box non-primitive arguments */
+  for (i = 0; i < n_params; i++)
+    {
+      GType type = param_types[i]  & ~G_SIGNAL_TYPE_STATIC_SCOPE;
+      GType fundamental = G_TYPE_FUNDAMENTAL (type);
+
+      atypes[i+1] = va_to_ffi_type (type,
+                                   &args_copy,
+                                   &storage[i]);
+      args[i+1] = &storage[i];
+
+      if ((param_types[i]  & G_SIGNAL_TYPE_STATIC_SCOPE) == 0)
+       {
+         if (fundamental == G_TYPE_STRING && storage[i]._gpointer != NULL)
+           storage[i]._gpointer = g_strdup (storage[i]._gpointer);
+         else if (fundamental == G_TYPE_PARAM && storage[i]._gpointer != NULL)
+           storage[i]._gpointer = g_param_spec_ref (storage[i]._gpointer);
+         else if (fundamental == G_TYPE_BOXED && storage[i]._gpointer != NULL)
+           storage[i]._gpointer = g_boxed_copy (type, storage[i]._gpointer);
+         else if (fundamental == G_TYPE_VARIANT && storage[i]._gpointer != NULL)
+           storage[i]._gpointer = g_variant_ref_sink (storage[i]._gpointer);
+       }
+      if (fundamental == G_TYPE_OBJECT && storage[i]._gpointer != NULL)
+       storage[i]._gpointer = g_object_ref (storage[i]._gpointer);
+    }
+
+  va_end (args_copy);
+  
+  if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, n_args, rtype, atypes) != FFI_OK)
+    return;
+
+  ffi_call (&cif, marshal_data ? marshal_data : cc->callback, rvalue, args);
+
+  /* Unbox non-primitive arguments */
+  for (i = 0; i < n_params; i++)
+    {
+      GType type = param_types[i]  & ~G_SIGNAL_TYPE_STATIC_SCOPE;
+      GType fundamental = G_TYPE_FUNDAMENTAL (type);
+
+      if ((param_types[i]  & G_SIGNAL_TYPE_STATIC_SCOPE) == 0)
+       {
+         if (fundamental == G_TYPE_STRING && storage[i]._gpointer != NULL)
+           g_free (storage[i]._gpointer);
+         else if (fundamental == G_TYPE_PARAM && storage[i]._gpointer != NULL)
+           g_param_spec_unref (storage[i]._gpointer);
+         else if (fundamental == G_TYPE_BOXED && storage[i]._gpointer != NULL)
+           g_boxed_free (type, storage[i]._gpointer);
+         else if (fundamental == G_TYPE_VARIANT && storage[i]._gpointer != NULL)
+           g_variant_unref (storage[i]._gpointer);
+       }
+      if (fundamental == G_TYPE_OBJECT && storage[i]._gpointer != NULL)
+       g_object_unref (storage[i]._gpointer);
+    }
+  
+  if (return_value && G_VALUE_TYPE (return_value))
+    value_from_ffi_type (return_value, rvalue);
+}
+
+/**
+ * g_cclosure_marshal_VOID__VOID:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 1
+ * @param_values: a #GValue array holding only the instance
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__BOOLEAN:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gboolean parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gboolean arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__CHAR:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gchar parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gchar arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__UCHAR:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #guchar parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, guchar arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__INT:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gint parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gint arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__UINT:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #guint parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, guint arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__LONG:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #glong parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, glong arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__ULONG:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gulong parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gulong arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__ENUM:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the enumeration parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gint arg1, gpointer user_data)` where the #gint parameter denotes an enumeration type..
+ */
+
+/**
+ * g_cclosure_marshal_VOID__FLAGS:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the flags parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gint arg1, gpointer user_data)` where the #gint parameter denotes a flags type.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__FLOAT:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gfloat parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gfloat arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__DOUBLE:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gdouble parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gdouble arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__STRING:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gchar* parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, const gchar *arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__PARAM:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #GParamSpec* parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, GParamSpec *arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__BOXED:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #GBoxed* parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, GBoxed *arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__POINTER:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #gpointer parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, gpointer arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__OBJECT:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #GObject* parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, GObject *arg1, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_VOID__VARIANT:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding the instance and the #GVariant* parameter
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, GVariant *arg1, gpointer user_data)`.
+ *
+ * Since: 2.26
+ */
+
+/**
+ * g_cclosure_marshal_VOID__UINT_POINTER:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: ignored
+ * @n_param_values: 3
+ * @param_values: a #GValue array holding instance, arg1 and arg2
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `void (*callback) (gpointer instance, guint arg1, gpointer arg2, gpointer user_data)`.
+ */
+
+/**
+ * g_cclosure_marshal_BOOLEAN__FLAGS:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: a #GValue which can store the returned #gboolean
+ * @n_param_values: 2
+ * @param_values: a #GValue array holding instance and arg1
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `gboolean (*callback) (gpointer instance, gint arg1, gpointer user_data)` where the #gint parameter
+ * denotes a flags type.
+ */
+
+/**
+ * g_cclosure_marshal_BOOL__FLAGS:
+ *
+ * Another name for g_cclosure_marshal_BOOLEAN__FLAGS().
+ */
+/**
+ * g_cclosure_marshal_STRING__OBJECT_POINTER:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: a #GValue, which can store the returned string
+ * @n_param_values: 3
+ * @param_values: a #GValue array holding instance, arg1 and arg2
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `gchar* (*callback) (gpointer instance, GObject *arg1, gpointer arg2, gpointer user_data)`.
+ */
+/**
+ * g_cclosure_marshal_BOOLEAN__OBJECT_BOXED_BOXED:
+ * @closure: the #GClosure to which the marshaller belongs
+ * @return_value: a #GValue, which can store the returned string
+ * @n_param_values: 3
+ * @param_values: a #GValue array holding instance, arg1 and arg2
+ * @invocation_hint: the invocation hint given as the last argument
+ *  to g_closure_invoke()
+ * @marshal_data: additional data specified when registering the marshaller
+ *
+ * A marshaller for a #GCClosure with a callback of type
+ * `gboolean (*callback) (gpointer instance, GBoxed *arg1, GBoxed *arg2, gpointer user_data)`.
+ *
+ * Since: 2.26
+ */