/src/glib/gobject/gclosure.c

Source
/* GObject - GLib Type, Object, Parameter and Signal Library
 * Copyright (C) 2000-2001 Red Hat, Inc.
 * Copyright (C) 2005 Imendio AB
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * 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, see <http://www.gnu.org/licenses/>.
 */

/*
 * MT safe with regards to reference counting.
 */

#include "config.h"

#include "../glib/gvalgrind.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"


/**
 * GClosure:
 * @in_marshal: Indicates whether the closure is currently being invoked with
 *   g_closure_invoke()
 * @is_invalid: Indicates whether the closure has been invalidated by
 *   g_closure_invalidate()
 *
 * 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][struct@Value] into
 * a suitable form, perform the callback on the converted arguments,
 * and transform the return value back into a [struct@Value].
 *
 * 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 [struct@Value] and native C types. The GObject
 * library provides the [struct@CClosure] type for this purpose. Bindings for
 * other languages need marshallers which convert between [GValues][struct@Value]
 * and suitable representations in the runtime of the language in
 * order to use functions written in that language as callbacks. Use
 * [method@Closure.set_marshal] to set the marshaller on such a custom
 * closure implementation.
 *
 * Within GObject, closures play an important role in the
 * implementation of signals. When a signal is registered, the
 * @c_marshaller argument to [func@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
 * [func@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 [struct@Closure] 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.
 *
 * - [method@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)    ((size_t) ((cl)->n_guards << 1L))
/* same as G_CLOSURE_N_NOTIFIERS() (keep in sync) */
#define CLOSURE_N_NOTIFIERS(cl)   ((size_t) (CLOSURE_N_MFUNCS (cl) + \
                                         (cl)->n_fnotifiers + \
                                         (cl)->n_inotifiers))

/* A copy of the flags bitfield from the beginning of `struct _GClosure`, which
 * is in union with an int for atomic access to all fields at the same time.
 *
 * This must be kept in sync with `struct _GClosure`, but that’s easy because
 * it’s (unfortunately) a public struct, so can never change for ABI
 * compatibility reasons. */
typedef union {
  struct {
    guint ref_count : 15;  /* (atomic) */
    /* meta_marshal is not used anymore but must be zero for historical reasons
       as it was exposed in the G_CLOSURE_N_NOTIFIERS macro */
    guint meta_marshal_nouse : 1;  /* (atomic) */
    guint n_guards : 1;  /* (atomic) */
    guint n_fnotifiers : 2;  /* finalization notifiers (atomic) */
    guint n_inotifiers : 8;  /* invalidation notifiers (atomic) */
    guint in_inotify : 1;  /* (atomic) */
    guint floating : 1;  /* (atomic) */
    guint derivative_flag : 1;  /* (atomic) */
    guint in_marshal : 1;  /* (atomic) */
    guint is_invalid : 1;  /* (atomic) */
  } flags;
  GClosure closure;
  int atomic_int;
} GClosureFlags;

G_STATIC_ASSERT (sizeof (GClosureFlags) == sizeof (GClosure));
G_STATIC_ASSERT (G_ALIGNOF (GClosureFlags) == G_ALIGNOF (GClosure));

#define ATOMIC_CHANGE_FIELD(_closure, _field, _OP, _value, _SET_OLD, _SET_NEW) \
G_STMT_START {                                                                          \
  GClosureFlags *cunion = (GClosureFlags *) _closure; \
  gint new_int, old_int, success;                                                 \
  old_int = g_atomic_int_get (&cunion->atomic_int); \
  do                                                                        \
    {                                                                       \
      GClosureFlags tmp; \
      tmp.atomic_int = old_int; \
      _SET_OLD tmp.flags._field; \
      tmp.flags._field _OP _value; \
      _SET_NEW tmp.flags._field; \
      new_int = tmp.atomic_int; \
      success = g_atomic_int_compare_and_exchange_full (&cunion->atomic_int, old_int, new_int, \
              &old_int);      \
    }                                                                       \
  while (!success); \
} G_STMT_END

#define ATOMIC_SWAP(_closure, _field, _value, _oldv)   ATOMIC_CHANGE_FIELD (_closure, _field, =, _value, *(_oldv) =,     (void) )
#define ATOMIC_SET(_closure, _field, _value)           ATOMIC_CHANGE_FIELD (_closure, _field, =, _value,     (void),     (void) )
#define ATOMIC_INC(_closure, _field)                   ATOMIC_CHANGE_FIELD (_closure, _field, +=,     1,     (void),     (void) )
#define ATOMIC_INC_ASSIGN(_closure, _field, _newv)     ATOMIC_CHANGE_FIELD (_closure, _field, +=,     1,     (void), *(_newv) = )
#define ATOMIC_DEC(_closure, _field)                   ATOMIC_CHANGE_FIELD (_closure, _field, -=,     1,     (void),     (void) )
#define ATOMIC_DEC_ASSIGN(_closure, _field, _newv)     ATOMIC_CHANGE_FIELD (_closure, _field, -=,     1,     (void), *(_newv) = )

static inline GClosureFlags
closure_atomic_get_flags (GClosure *closure)
{
  GClosureFlags tmp;
  tmp.atomic_int = g_atomic_int_get (&((GClosureFlags *) closure)->atomic_int);
  return tmp;
}

enum {
  FNOTIFY,
  INOTIFY,
  PRE_NOTIFY,
  POST_NOTIFY
};

#if defined(FFI_VERSION_NUMBER) && FFI_VERSION_NUMBER >= 30700

typedef struct
{
  ffi_cif         cif;
  ffi_call_plan  *plan;
  ffi_type      **atypes;
  ffi_type       *rtype;
  ffi_abi         abi;
  guint           n_args;
} GClosureMarshalCallPlan;

typedef struct
{
  GMutex      lock;
  GHashTable *plans;
} GClosureMarshalPlanCache;

/* Like quarks, the cache and its entries live for the lifetime of the process. */
static GClosureMarshalPlanCache marshal_plan_cache;

static void
closure_marshal_call_plan_free (GClosureMarshalCallPlan *call_plan)
{
  g_clear_pointer (&call_plan->plan, ffi_call_plan_free);
  g_clear_pointer (&call_plan->atypes, g_free);
  g_free (call_plan);
}

static GClosureMarshalCallPlan *
closure_marshal_call_plan_new (ffi_abi    abi,
                               guint      n_args,
                               ffi_type  *rtype,
                               ffi_type **atypes)
{
  GClosureMarshalCallPlan *call_plan;

  g_assert (rtype != NULL);
  g_assert (atypes != NULL);

  call_plan = g_new0 (GClosureMarshalCallPlan, 1);
  call_plan->atypes = g_new0 (ffi_type *, n_args);
  memcpy (call_plan->atypes, atypes, sizeof (*atypes) * n_args);
  call_plan->rtype = rtype;
  call_plan->abi = abi;
  call_plan->n_args = n_args;

  if (ffi_prep_cif (&call_plan->cif,
                    call_plan->abi,
                    call_plan->n_args,
                    call_plan->rtype,
                    call_plan->atypes) != FFI_OK)
    {
      closure_marshal_call_plan_free (call_plan);
      return NULL;
    }

  if (!(call_plan->plan = ffi_call_plan_alloc (&call_plan->cif)))
    {
      closure_marshal_call_plan_free (call_plan);
      return NULL;
    }

  return call_plan;
}

static gboolean
closure_marshal_call_plan_matches (const GClosureMarshalCallPlan  *call_plan,
                                   ffi_abi                         abi,
                                   guint                           n_args,
                                   ffi_type                       *rtype,
                                   ffi_type                      **atypes)
{
  g_assert (call_plan != NULL);
  g_assert (rtype != NULL);
  g_assert (atypes != NULL);

  return call_plan->abi == abi &&
         call_plan->n_args == n_args &&
         call_plan->rtype == rtype &&
         memcmp (call_plan->atypes, atypes, sizeof (*atypes) * n_args) == 0;
}

static guint
closure_marshal_call_plan_hash (gconstpointer data)
{
  const GClosureMarshalCallPlan *call_plan = data;
  guint hash;
  guint i;

  hash = (guint) call_plan->abi;
  hash = (hash * 33) ^ call_plan->n_args;
  hash = (hash * 33) ^ g_direct_hash (call_plan->rtype);

  for (i = 0; i < call_plan->n_args; i++)
    hash = (hash * 33) ^ g_direct_hash (call_plan->atypes[i]);

  return hash;
}

static gboolean
closure_marshal_call_plan_equal (gconstpointer data_a,
                                 gconstpointer data_b)
{
  const GClosureMarshalCallPlan *call_plan_a = data_a;
  const GClosureMarshalCallPlan *call_plan_b = data_b;

  return closure_marshal_call_plan_matches (call_plan_a,
                                            call_plan_b->abi,
                                            call_plan_b->n_args,
                                            call_plan_b->rtype,
                                            call_plan_b->atypes);
}

static GClosureMarshalCallPlan *
closure_marshal_plan_cache_lookup_unlocked (GClosureMarshalPlanCache  *cache,
                                            ffi_abi                    abi,
                                            guint                      n_args,
                                            ffi_type                  *rtype,
                                            ffi_type                 **atypes)
{
  GClosureMarshalCallPlan lookup = { 0, };

  if (cache->plans == NULL)
    return NULL;

  lookup.atypes = atypes;
  lookup.rtype = rtype;
  lookup.abi = abi;
  lookup.n_args = n_args;

  return g_hash_table_lookup (cache->plans, &lookup);
}

static GClosureMarshalCallPlan *
closure_marshal_plan_cache_get (ffi_abi    abi,
                                guint      n_args,
                                ffi_type  *rtype,
                                ffi_type **atypes)
{
  GClosureMarshalCallPlan *call_plan;
  GClosureMarshalCallPlan *candidate;

  g_mutex_lock (&marshal_plan_cache.lock);
  call_plan = closure_marshal_plan_cache_lookup_unlocked (&marshal_plan_cache,
                                                          abi,
                                                          n_args,
                                                          rtype,
                                                          atypes);
  g_mutex_unlock (&marshal_plan_cache.lock);

  if (call_plan != NULL)
    return call_plan;

  if (!(candidate = closure_marshal_call_plan_new (abi, n_args, rtype, atypes)))
    return NULL;

  g_mutex_lock (&marshal_plan_cache.lock);

  if (marshal_plan_cache.plans == NULL)
    marshal_plan_cache.plans =
      g_hash_table_new_full (closure_marshal_call_plan_hash,
                             closure_marshal_call_plan_equal,
                             (GDestroyNotify) closure_marshal_call_plan_free,
                             NULL);

  call_plan = closure_marshal_plan_cache_lookup_unlocked (&marshal_plan_cache,
                                                          abi,
                                                          n_args,
                                                          rtype,
                                                          atypes);

  if (call_plan == NULL)
    {
      call_plan = g_steal_pointer (&candidate);
      g_hash_table_add (marshal_plan_cache.plans, call_plan);
    }

  g_mutex_unlock (&marshal_plan_cache.lock);

  g_clear_pointer (&candidate, closure_marshal_call_plan_free);

  return call_plan;
}

static gboolean
closure_marshal_call_plan_invoke (GClosure  *closure,
                                  ffi_abi    abi,
                                  guint      n_args,
                                  ffi_type  *rtype,
                                  ffi_type **atypes,
                                  void     (*callback) (void),
                                  void      *rvalue,
                                  void     **args)
{
  GRealClosure *real_closure;
  GClosureMarshalCallPlan *call_plan;

  g_assert (closure != NULL);
  g_assert (rtype != NULL);
  g_assert (atypes != NULL);
  g_assert (callback != NULL);
  g_assert (args != NULL);

  real_closure = G_REAL_CLOSURE (closure);
  call_plan = g_atomic_pointer_get (&real_closure->marshal_call_plan);

  if (call_plan == NULL ||
      !closure_marshal_call_plan_matches (call_plan, abi, n_args, rtype, atypes))
    {
      if (!(call_plan = closure_marshal_plan_cache_get (abi, n_args, rtype, atypes)))
        return FALSE;

      /* Concurrent invocations may cache different signatures; each uses its
       * own local plan, and the next invocation checks the cached signature. */
      g_atomic_pointer_set (&real_closure->marshal_call_plan, call_plan);
    }

  ffi_call_plan_invoke (call_plan->plan, callback, rvalue, args);

  return TRUE;
}

#endif /* FFI_VERSION_NUMBER >= 30700 */

/* --- 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 floating): a floating reference to a new #GClosure
 */
GClosure*
g_closure_new_simple (guint           sizeof_closure,
          gpointer        data)
{
  GClosure *closure;
  size_t private_size;
  gchar *allocated;

  g_return_val_if_fail (sizeof_closure >= sizeof (GClosure), NULL);

  private_size = sizeof (GRealClosure) - sizeof (GClosure);

#ifdef ENABLE_VALGRIND
  /* See comments in gtype.c about what's going on here... */
  if (RUNNING_ON_VALGRIND)
    {
      private_size += sizeof (gpointer);

      allocated = g_malloc0 (private_size + sizeof_closure + sizeof (gpointer));

      *(gpointer *) (allocated + private_size + sizeof_closure) = allocated + sizeof (gpointer);

      VALGRIND_MALLOCLIKE_BLOCK (allocated + private_size, sizeof_closure + sizeof (gpointer), 0, TRUE);
      VALGRIND_MALLOCLIKE_BLOCK (allocated + sizeof (gpointer), private_size - sizeof (gpointer), 0, TRUE);
    }
  else
#endif
    allocated = g_malloc0 (private_size + sizeof_closure);

  closure = (GClosure *) (allocated + private_size);

  ATOMIC_SET (closure, ref_count, 1);
  ATOMIC_SET (closure, floating, TRUE);
  closure->data = data;

  return closure;
}

static inline void
closure_invoke_notifiers (GClosure *closure,
        guint     notify_type)
{
  /* notifier layout:
   *     n_guards    n_guards     n_fnotif.  n_inotifiers
   * ->[[pre_guards][post_guards][fnotifiers][inotifiers]]
   *
   * 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
   * - 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
   * + none of the callbacks can cause recursion
   * + closure->n_inotifiers is const 0 during FNOTIFY
   */
  switch (notify_type)
    {
      GClosureNotifyData *ndata;
      guint i, offs;
    case FNOTIFY:
      while (closure->n_fnotifiers)
  {
          guint n;
    ATOMIC_DEC_ASSIGN (closure, n_fnotifiers, &n);

    ndata = closure->notifiers + CLOSURE_N_MFUNCS (closure) + n;
    closure->marshal = (GClosureMarshal) ndata->notify;
    closure->data = ndata->data;
    ndata->notify (ndata->data, closure);
  }
      closure->marshal = NULL;
      closure->data = NULL;
      break;
    case INOTIFY:
      ATOMIC_SET (closure, in_inotify, TRUE);
      while (closure->n_inotifiers)
  {
          guint n;
          ATOMIC_DEC_ASSIGN (closure, n_inotifiers, &n);

    ndata = closure->notifiers + CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers + n;
    closure->marshal = (GClosureMarshal) ndata->notify;
    closure->data = ndata->data;
    ndata->notify (ndata->data, closure);
  }
      closure->marshal = NULL;
      closure->data = NULL;
      ATOMIC_SET (closure, in_inotify, FALSE);
      break;
    case PRE_NOTIFY:
      i = closure->n_guards;
      offs = 0;
      while (i--)
  {
    ndata = closure->notifiers + offs + i;
    ndata->notify (ndata->data, closure);
  }
      break;
    case POST_NOTIFY:
      i = closure->n_guards;
      offs = i;
      while (i--)
  {
    ndata = closure->notifiers + offs + i;
    ndata->notify (ndata->data, closure);
  }
      break;
    }
}

static void
g_closure_set_meta_va_marshal (GClosure       *closure,
             GVaClosureMarshal va_meta_marshal)
{
  GClosureFlags old_flags;
  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (va_meta_marshal != NULL);

  old_flags = closure_atomic_get_flags (closure);
  g_return_if_fail (!old_flags.flags.is_invalid);
  g_return_if_fail (!old_flags.flags.in_marshal);

  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: (closure meta_marshal): context-dependent data to pass
 *  to @meta_marshal
 * @meta_marshal: a #GClosureMarshal function
 *
 * Sets the meta marshaller of @closure.
 *
 * A meta marshaller wraps the @closure's 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 the @closure's 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)
{
  GClosureFlags old_flags;
  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (meta_marshal != NULL);

  old_flags = closure_atomic_get_flags (closure);
  g_return_if_fail (!old_flags.flags.is_invalid);
  g_return_if_fail (!old_flags.flags.in_marshal);

  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: (closure pre_marshal_notify): data to pass
 *  to @pre_marshal_notify
 * @pre_marshal_notify: a function to call before the closure callback
 * @post_marshal_data: (closure post_marshal_notify): 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,
            GClosureNotify pre_marshal_notify,
            gpointer       post_marshal_data,
            GClosureNotify post_marshal_notify)
{
  GClosureFlags old_flags;
  guint i;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (pre_marshal_notify != NULL);
  g_return_if_fail (post_marshal_notify != NULL);

  old_flags = closure_atomic_get_flags (closure);
  g_return_if_fail (!old_flags.flags.is_invalid);
  g_return_if_fail (!old_flags.flags.in_marshal);
  g_return_if_fail (old_flags.flags.n_guards < CLOSURE_MAX_N_GUARDS);

  closure->notifiers = g_renew (GClosureNotifyData, closure->notifiers, CLOSURE_N_NOTIFIERS (closure) + 2);
  if (closure->n_inotifiers)
    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
      closure->n_fnotifiers +
      closure->n_inotifiers + 1)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
                    closure->n_fnotifiers + 0)];
  if (closure->n_inotifiers > 1)
    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
      closure->n_fnotifiers +
      closure->n_inotifiers)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
                      closure->n_fnotifiers + 1)];
  if (closure->n_fnotifiers)
    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
      closure->n_fnotifiers + 1)] = closure->notifiers[CLOSURE_N_MFUNCS (closure) + 0];
  if (closure->n_fnotifiers > 1)
    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
      closure->n_fnotifiers)] = closure->notifiers[CLOSURE_N_MFUNCS (closure) + 1];
  if (closure->n_guards)
    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;
  ATOMIC_INC (closure, n_guards);
}

/**
 * g_closure_add_finalize_notifier: (skip)
 * @closure: a #GClosure
 * @notify_data: (closure notify_func): 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_finalize_notifier (GClosure      *closure,
         gpointer       notify_data,
         GClosureNotify notify_func)
{
  size_t i;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (notify_func != NULL);
  g_return_if_fail (closure->n_fnotifiers < CLOSURE_MAX_N_FNOTIFIERS);

  closure->notifiers = g_renew (GClosureNotifyData, closure->notifiers, CLOSURE_N_NOTIFIERS (closure) + 1);
  if (closure->n_inotifiers)
    closure->notifiers[(CLOSURE_N_MFUNCS (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;
  closure->notifiers[i].data = notify_data;
  closure->notifiers[i].notify = notify_func;
  ATOMIC_INC (closure, n_fnotifiers);
}

/**
 * g_closure_add_invalidate_notifier: (skip)
 * @closure: a #GClosure
 * @notify_data: (closure notify_func): 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_invalidate_notifier (GClosure      *closure,
           gpointer       notify_data,
           GClosureNotify notify_func)
{
  GClosureFlags old_flags;
  size_t i;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (notify_func != NULL);

  old_flags = closure_atomic_get_flags (closure);
  g_return_if_fail (!old_flags.flags.is_invalid);
  g_return_if_fail (old_flags.flags.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;
  closure->notifiers[i].data = notify_data;
  closure->notifiers[i].notify = notify_func;
  ATOMIC_INC (closure, n_inotifiers);
}

static inline gboolean
closure_try_remove_inotify (GClosure       *closure,
          gpointer       notify_data,
          GClosureNotify notify_func)
{
  GClosureNotifyData *ndata, *nlast;

  nlast = closure->notifiers + CLOSURE_N_NOTIFIERS (closure) - 1;
  for (ndata = nlast + 1 - closure->n_inotifiers; ndata <= nlast; ndata++)
    if (ndata->notify == notify_func && ndata->data == notify_data)
      {
  ATOMIC_DEC (closure, n_inotifiers);
  if (ndata < nlast)
    *ndata = *nlast;

  return TRUE;
      }
  return FALSE;
}

static inline gboolean
closure_try_remove_fnotify (GClosure       *closure,
          gpointer       notify_data,
          GClosureNotify notify_func)
{
  GClosureNotifyData *ndata, *nlast;

  nlast = closure->notifiers + CLOSURE_N_NOTIFIERS (closure) - closure->n_inotifiers - 1;
  for (ndata = nlast + 1 - closure->n_fnotifiers; ndata <= nlast; ndata++)
    if (ndata->notify == notify_func && ndata->data == notify_data)
      {
  ATOMIC_DEC (closure, n_fnotifiers);
  if (ndata < nlast)
    *ndata = *nlast;
  if (closure->n_inotifiers)
    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
            closure->n_fnotifiers)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +
                      closure->n_fnotifiers +
                      closure->n_inotifiers)];
  return TRUE;
      }
  return FALSE;
}

static GClosureFlags
closure_ref_internal (GClosure *closure)
{
  guint new_ref_count;
  int old_int, success;
  GClosureFlags tmp = { .atomic_int = 0, };

  old_int = g_atomic_int_get (&((GClosureFlags *) closure)->atomic_int);
  do
    {
      tmp.atomic_int = old_int;
      tmp.flags.ref_count += 1;
      success = g_atomic_int_compare_and_exchange_full (&((GClosureFlags *) closure)->atomic_int, old_int, tmp.atomic_int, &old_int);
    }
  while (!success);

  new_ref_count = tmp.flags.ref_count;

  g_return_val_if_fail (new_ref_count > 1, tmp);
  g_return_val_if_fail (new_ref_count < CLOSURE_MAX_REF_COUNT + 1, tmp);

  return tmp;
}

/**
 * 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 full): The @closure passed in, for convenience
 */
GClosure*
g_closure_ref (GClosure *closure)
{
  g_return_val_if_fail (closure != NULL, NULL);

  closure_ref_internal (closure);
  return closure;
}

static void
closure_invalidate_internal (GClosure *closure)
{
  gboolean was_invalid;

  ATOMIC_SWAP (closure, is_invalid, TRUE, &was_invalid);
  /* invalidate only once */
  if (!was_invalid)
    closure_invoke_notifiers (closure, INOTIFY);
}

/**
 * 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)
{
  GClosureFlags old_flags;

  g_return_if_fail (closure != NULL);

  old_flags = closure_atomic_get_flags (closure);
  if (!old_flags.flags.is_invalid)
    {
      g_closure_ref (closure);           /* preserve floating flag */
      closure_invalidate_internal (closure);
      g_closure_unref (closure);
    }
}

/**
 * g_closure_unref:
 * @closure: (transfer full): #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;
  GClosureFlags old_flags;

  g_return_if_fail (closure != NULL);

  old_flags = closure_atomic_get_flags (closure);
  g_return_if_fail (old_flags.flags.ref_count > 0);

  /* last unref, invalidate first */
  if (old_flags.flags.ref_count == 1 && !old_flags.flags.is_invalid)
    closure_invalidate_internal (closure);

  ATOMIC_DEC_ASSIGN (closure, ref_count, &new_ref_count);

  if (new_ref_count == 0)
    {
      closure_invoke_notifiers (closure, FNOTIFY);
      g_free (closure->notifiers);

#ifdef ENABLE_VALGRIND
      /* See comments in gtype.c about what's going on here... */
      if (RUNNING_ON_VALGRIND)
        {
          gchar *allocated;

          allocated = (gchar *) G_REAL_CLOSURE (closure);
          allocated -= sizeof (gpointer);

          g_free (allocated);

          VALGRIND_FREELIKE_BLOCK (allocated + sizeof (gpointer), 0);
          VALGRIND_FREELIKE_BLOCK (closure, 0);
        }
      else
#endif
        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.
 *
 * This function 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(). An 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)
{
  GClosureFlags old_flags;

  g_return_if_fail (closure != NULL);

  old_flags = closure_atomic_get_flags (closure);
  g_return_if_fail (old_flags.flags.ref_count > 0);

  /* floating is basically a kludge to avoid creating closures
   * 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 initial ref_count.
   */
  if (old_flags.flags.floating)
    {
      gboolean was_floating;
      ATOMIC_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_invalidate_notifier (GClosure      *closure,
              gpointer       notify_data,
              GClosureNotify notify_func)
{
  GClosureFlags old_flags;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (notify_func != NULL);

  old_flags = closure_atomic_get_flags (closure);

  if (old_flags.flags.is_invalid && old_flags.flags.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_critical (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_finalize_notifier (GClosure      *closure,
            gpointer       notify_data,
            GClosureNotify notify_func)
{
  GClosureFlags old_flags;

  g_return_if_fail (closure != NULL);
  g_return_if_fail (notify_func != NULL);

  old_flags = closure_atomic_get_flags (closure);

  if (old_flags.flags.is_invalid && !old_flags.flags.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_critical (G_STRLOC ": unable to remove uninstalled finalization notifier: %p (%p)",
                notify_func, notify_data);
}

/**
 * g_closure_invoke:
 * @closure: a #GClosure
 * @return_value: (optional) (out): 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: (nullable): 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,
      guint           n_param_values,
      const GValue   *param_values,
      gpointer        invocation_hint)
{
  GClosureFlags reffed_flags;
  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  real_closure = G_REAL_CLOSURE (closure);

  reffed_flags = closure_ref_internal (closure);  /* preserve floating flag */
  if (!reffed_flags.flags.is_invalid)
    {
      GClosureMarshal marshal;
      gpointer marshal_data;
      gboolean in_marshal = reffed_flags.flags.in_marshal;

      g_return_if_fail (closure->marshal || real_closure->meta_marshal);

      ATOMIC_SET (closure, in_marshal, TRUE);
      if (real_closure->meta_marshal)
  {
    marshal_data = real_closure->meta_marshal_data;
    marshal = real_closure->meta_marshal;
  }
      else
  {
    marshal_data = NULL;
    marshal = closure->marshal;
  }
      if (!in_marshal)
  closure_invoke_notifiers (closure, PRE_NOTIFY);
      marshal (closure,
         return_value,
         n_param_values, param_values,
         invocation_hint,
         marshal_data);
      if (!in_marshal)
  closure_invoke_notifiers (closure, POST_NOTIFY);
      ATOMIC_SET (closure, in_marshal, (guint) 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)
{
  GClosureFlags reffed_flags;
  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  real_closure = G_REAL_CLOSURE (closure);

  reffed_flags = closure_ref_internal (closure);  /* preserve floating flag */
  if (!reffed_flags.flags.is_invalid)
    {
      GVaClosureMarshal marshal;
      gpointer marshal_data;
      gboolean in_marshal = reffed_flags.flags.in_marshal;

      g_return_if_fail (closure->marshal || real_closure->meta_marshal);

      ATOMIC_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);
      ATOMIC_SET (closure, in_marshal, (guint) 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.
 *
 * For GObject's C predefined marshallers (the `g_cclosure_marshal_*()`
 * functions), what it provides is a callback function to use instead of
 * @closure->callback.
 *
 * See also: g_closure_set_meta_marshal()
 */
void
g_closure_set_marshal (GClosure       *closure,
           GClosureMarshal marshal)
{
  g_return_if_fail (closure != NULL);
  g_return_if_fail (marshal != NULL);

  if (closure->marshal && closure->marshal != marshal)
    g_critical ("attempt to override closure->marshal (%p) with new marshal (%p)",
          closure->marshal, marshal);
  else
    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_critical ("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: (closure user_data): 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.
 *
 * @destroy_data will be called as a finalize notifier on the #GClosure.
 *
 * Returns: (transfer floating): a floating reference to a new #GCClosure
 */
GClosure*
g_cclosure_new (GCallback      callback_func,
    gpointer       user_data,
    GClosureNotify destroy_data)
{
  GClosure *closure;
  
  g_return_val_if_fail (callback_func != NULL, NULL);
  
  closure = g_closure_new_simple (sizeof (GCClosure), user_data);
  if (destroy_data)
    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: (closure user_data): 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.
 *
 * @destroy_data will be called as a finalize notifier on the #GClosure.
 *
 * Returns: (transfer floating): a floating reference to a new #GCClosure
 */
GClosure*
g_cclosure_new_swap (GCallback      callback_func,
         gpointer       user_data,
         GClosureNotify destroy_data)
{
  GClosure *closure;
  
  g_return_val_if_fail (callback_func != NULL, NULL);
  
  closure = g_closure_new_simple (sizeof (GCClosure), user_data);
  if (destroy_data)
    g_closure_add_finalize_notifier (closure, user_data, destroy_data);
  ((GCClosure*) closure)->callback = (gpointer) callback_func;
  ATOMIC_SET (closure, derivative_flag, TRUE);
  
  return closure;
}

static void
g_type_class_meta_marshal (GClosure       *closure,
         GValue /*out*/ *return_value,
         guint           n_param_values,
         const GValue   *param_values,
         gpointer        invocation_hint,
         gpointer        marshal_data)
{
  GTypeClass *class;
  gpointer callback;
  /* 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);
  callback = G_STRUCT_MEMBER (gpointer, class, offset);
  if (callback)
    closure->marshal (closure,
          return_value,
          n_param_values, param_values,
          invocation_hint,
          callback);
}

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,
         const GValue   *param_values,
         gpointer        invocation_hint,
         gpointer        marshal_data)
{
  GTypeClass *class;
  gpointer callback;
  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);
  callback = G_STRUCT_MEMBER (gpointer, class, offset);
  if (callback)
    closure->marshal (closure,
          return_value,
          n_param_values, param_values,
          invocation_hint,
          callback);
}

gboolean
_g_closure_is_void (GClosure *closure,
        gpointer instance)
{
  GClosureFlags old_flags;
  GRealClosure *real_closure;
  GTypeClass *class;
  gpointer callback;
  GType itype;
  guint offset;

  old_flags = closure_atomic_get_flags (closure);

  if (old_flags.flags.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: (transfer floating): a floating reference to a new #GCClosure
 */
GClosure*
g_signal_type_cclosure_new (GType    itype,
          guint    struct_offset)
{
  GClosure *closure;
  
  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), GTYPE_TO_POINTER (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_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_va_marshal (closure, g_type_class_meta_marshalv);
    }
  return closure;
}

/*
 * A custom pointer-compatible value type is an instantiatable type whose
 * GTypeValueTable stores the value as a pointer, exposes it with
 * value_peek_pointer(), and collects it from varargs as a gpointer.
 *
 * This covers custom GTypeInstance-derived fundamental types which are not
 * GObjects, such as a library-defined object type registered with
 * g_type_register_fundamental(). It intentionally excludes the built-in
 * pointer-like fundamental types handled by the marshaller's normal cases.
 */
static gboolean
value_type_is_custom_pointer_compatible (GType type)
{
  GTypeValueTable *value_table;

  switch (g_type_fundamental (type))
    {
    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:
      return FALSE;

    default:
      break;
    }

  value_table = g_type_value_table_peek (type);

  return G_TYPE_IS_INSTANTIATABLE (type) &&
         value_table != NULL &&
         value_table->value_peek_pointer != NULL &&
         value_table->collect_format != NULL &&
         strcmp (value_table->collect_format, "p") == 0;
}

static ffi_type *
value_to_ffi_type (const GValue *gvalue,
                   gpointer *value,
                   gint *enum_tmpval,
                   gpointer *pointer_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_FLAGS:
      g_assert (enum_tmpval != NULL);
      rettype = &ffi_type_uint;
      *enum_tmpval = (int) g_value_get_flags (gvalue);
      *value = enum_tmpval;
      *tmpval_used = TRUE;
      break;
    case G_TYPE_UCHAR:
    case G_TYPE_UINT:
      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;
      if (value_type_is_custom_pointer_compatible (G_VALUE_TYPE (gvalue)))
        {
          g_assert (pointer_tmpval != NULL);
          *pointer_tmpval = g_value_peek_pointer (gvalue);
          *value = pointer_tmpval;
          *tmpval_used = TRUE;
        }
      else
        {
          *value = NULL;
          g_critical ("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;
  GType type;

  type = G_VALUE_TYPE (gvalue);

restart:
  switch (g_type_fundamental (type))
    {
    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;
    case G_TYPE_INTERFACE:
      type = g_type_interface_instantiatable_prerequisite (type);
      if (type)
        goto restart;
      G_GNUC_FALLTHROUGH;
    default:
      if (value_type_is_custom_pointer_compatible (G_VALUE_TYPE (gvalue)))
        {
          GTypeValueTable *value_table = g_type_value_table_peek (G_VALUE_TYPE (gvalue));

          if (value_table->value_free != NULL)
            value_table->value_free (gvalue);
          gvalue->data[0].v_pointer = *(gpointer*) value;
        }
      else
        {
          g_critical ("value_from_ffi_type: Unsupported fundamental type %s for type %s",
                      g_type_name (g_type_fundamental (G_VALUE_TYPE (gvalue))),
                      g_type_name (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;
      if (value_type_is_custom_pointer_compatible (gtype))
        storage->_gpointer = va_arg (*va, gpointer);
      else
        {
          storage->_guint64  = 0;
          g_critical ("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;
  size_t n_args;
  ffi_type **atypes;
  void **args;
  size_t i;
  ffi_cif cif;
  GCClosure *cc = (GCClosure*) closure;
  gint *enum_tmpval;
  gpointer *pointer_tmpval;
  gboolean tmpval_used = FALSE;

  enum_tmpval = g_alloca (sizeof (gint));
  pointer_tmpval = g_alloca (sizeof (gpointer));
  if (return_gvalue && G_VALUE_TYPE (return_gvalue))
    {
      rtype = value_to_ffi_type (return_gvalue, &rvalue, enum_tmpval, pointer_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));
      pointer_tmpval = g_alloca (sizeof (gpointer));
    }

  if (G_CCLOSURE_SWAP_DATA (closure))
    {
      atypes[n_args-1] = value_to_ffi_type (param_values + 0,
                                            &args[n_args-1],
                                            enum_tmpval,
                                            pointer_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,
                                     pointer_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));
          pointer_tmpval = g_alloca (sizeof (gpointer));
        }

      atypes[i] = value_to_ffi_type (param_values + i,
                                     &args[i],
                                     enum_tmpval,
                                     pointer_tmpval,
                                     &tmpval_used);
    }

  g_assert (n_args <= UINT_MAX);

#if defined(FFI_VERSION_NUMBER) && FFI_VERSION_NUMBER >= 30700
  if (!closure_marshal_call_plan_invoke (closure,
                                         FFI_DEFAULT_ABI,
                                         (guint) n_args,
                                         rtype,
                                         atypes,
                                         FFI_FN (marshal_data ? marshal_data : cc->callback),
                                         rvalue,
                                         args))
    {
      if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, (unsigned int) n_args, rtype, atypes) != FFI_OK)
        return;

      ffi_call (&cif,
                FFI_FN (marshal_data ? marshal_data : cc->callback),
                rvalue,
                args);
    }
#else
  if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, (unsigned int) n_args, rtype, atypes) != FFI_OK)
    return;

  ffi_call (&cif, FFI_FN (marshal_data ? marshal_data : cc->callback), rvalue, args);
#endif

  if (return_gvalue && G_VALUE_TYPE (return_gvalue))
    value_from_ffi_type (return_gvalue, rvalue);
}

/**
 * g_cclosure_marshal_generic_va:
 * @closure: the #GClosure to which the marshaller belongs
 * @return_value: (nullable): a #GValue to store the return
 *  value. May be %NULL if the callback of @closure doesn't return a
 *  value.
 * @instance: (type GObject.TypeInstance): the instance on which the closure is
 *  invoked.
 * @args_list: va_list of arguments to be passed to the closure.
 * @marshal_data: (nullable): additional data specified when
 *  registering the marshaller, see g_closure_set_marshal() and
 *  g_closure_set_meta_marshal()
 * @n_params: the length of the @param_types array
 * @param_types: (array length=n_params): the #GType of each argument from
 *  @args_list.
 *
 * A generic #GVaClosureMarshal function implemented via
 * [libffi](http://sourceware.org/libffi/).
 *
 * Since: 2.30
 */
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;
  size_t n_args;
  size_t unsigned_n_params;
  ffi_type **atypes;
  void **args;
  va_arg_storage *storage;
  size_t i;
  ffi_cif cif;
  GCClosure *cc = (GCClosure*) closure;
  gint *enum_tmpval;
  gpointer *pointer_tmpval;
  gboolean tmpval_used = FALSE;
  gboolean call_succeeded = FALSE;
  va_list args_copy;
  GValue *value_storage;

  g_return_if_fail (n_params >= 0);

  unsigned_n_params = (size_t) n_params;

  enum_tmpval = g_alloca (sizeof (gint));
  pointer_tmpval = g_alloca (sizeof (gpointer));
  if (return_value && G_VALUE_TYPE (return_value))
    {
      rtype = value_to_ffi_type (return_value, &rvalue, enum_tmpval, pointer_tmpval, &tmpval_used);
    }
  else
    {
      rtype = &ffi_type_void;
    }

  rvalue = g_alloca (MAX (rtype->size, sizeof (ffi_arg)));

  n_args = unsigned_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) * unsigned_n_params);
  value_storage = g_alloca (sizeof (GValue) * unsigned_n_params);
  memset (value_storage, 0, sizeof (GValue) * unsigned_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;
    }

  va_copy (args_copy, args_list);

  /* Box non-primitive arguments */
  for (i = 0; i < unsigned_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);
    else if (value_type_is_custom_pointer_compatible (type))
      {
        g_value_init (&value_storage[i], type);
        g_value_set_instance (&value_storage[i], storage[i]._gpointer);
        storage[i]._gpointer = g_value_peek_pointer (&value_storage[i]);
      }
  }
      if (fundamental == G_TYPE_OBJECT && storage[i]._gpointer != NULL)
  storage[i]._gpointer = g_object_ref (storage[i]._gpointer);
    }

  va_end (args_copy);

  g_assert (n_args <= UINT_MAX);

#if defined(FFI_VERSION_NUMBER) && FFI_VERSION_NUMBER >= 30700
  if (closure_marshal_call_plan_invoke (closure,
                                        FFI_DEFAULT_ABI,
                                        (guint) n_args,
                                        rtype,
                                        atypes,
                                        FFI_FN (marshal_data ? marshal_data : cc->callback),
                                        rvalue,
                                        args))
    {
      call_succeeded = TRUE;
    }
  else if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, (unsigned int) n_args, rtype, atypes) == FFI_OK)
    {
      ffi_call (&cif,
                FFI_FN (marshal_data ? marshal_data : cc->callback),
                rvalue,
                args);
      call_succeeded = TRUE;
    }
#else
  if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, (unsigned int) n_args, rtype, atypes) == FFI_OK)
    {
      ffi_call (&cif, FFI_FN (marshal_data ? marshal_data : cc->callback), rvalue, args);
      call_succeeded = TRUE;
    }
#endif

  /* Unbox non-primitive arguments */
  for (i = 0; i < unsigned_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);
    else if (G_VALUE_TYPE (&value_storage[i]) != 0)
      g_value_unset (&value_storage[i]);
  }
      if (fundamental == G_TYPE_OBJECT && storage[i]._gpointer != NULL)
  g_object_unref (storage[i]._gpointer);
    }

  if (call_succeeded && return_value && G_VALUE_TYPE (return_value))
    value_from_ffi_type (return_value, rvalue);
}

Coverage Report

Created: 2026-10-28 06:22