gtype.c

/* GObject - GLib Type, Object, Parameter and Signal Library
 * Copyright (C) 1998-1999, 2000-2001 Tim Janik and Red Hat, Inc.
 *
 * 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
 */

#include "config.h"

#include "../glib/gvalgrind.h"
#include <string.h>

#include "gtype.h"
#include "gtype-private.h"
#include "gtypeplugin.h"
#include "gvaluecollector.h"
#include "gatomicarray.h"
#include "gobject_trace.h"

#include "glib-private.h"
#include "gconstructor.h"

#ifdef G_OS_WIN32
#include <windows.h>
#endif

#ifdef	G_ENABLE_DEBUG
#define	IF_DEBUG(debug_type)	if (_g_type_debug_flags & G_TYPE_DEBUG_ ## debug_type)
#endif

/**
 * SECTION:gtype
 * @short_description: The GLib Runtime type identification and
 *     management system
 * @title:Type Information
 *
 * The GType API is the foundation of the GObject system. It provides the
 * facilities for registering and managing all fundamental data types,
 * user-defined object and interface types.
 *
 * For type creation and registration purposes, all types fall into one of
 * two categories: static or dynamic.  Static types are never loaded or
 * unloaded at run-time as dynamic types may be.  Static types are created
 * with g_type_register_static() that gets type specific information passed
 * in via a #GTypeInfo structure.
 *
 * Dynamic types are created with g_type_register_dynamic() which takes a
 * #GTypePlugin structure instead. The remaining type information (the
 * #GTypeInfo structure) is retrieved during runtime through #GTypePlugin
 * and the g_type_plugin_*() API.
 *
 * These registration functions are usually called only once from a
 * function whose only purpose is to return the type identifier for a
 * specific class.  Once the type (or class or interface) is registered,
 * it may be instantiated, inherited, or implemented depending on exactly
 * what sort of type it is.
 *
 * There is also a third registration function for registering fundamental
 * types called g_type_register_fundamental() which requires both a #GTypeInfo
 * structure and a #GTypeFundamentalInfo structure but it is seldom used
 * since most fundamental types are predefined rather than user-defined.
 *
 * Type instance and class structs are limited to a total of 64 KiB,
 * including all parent types. Similarly, type instances' private data
 * (as created by G_ADD_PRIVATE()) are limited to a total of
 * 64 KiB. If a type instance needs a large static buffer, allocate it
 * separately (typically by using #GArray or #GPtrArray) and put a pointer
 * to the buffer in the structure.
 *
 * As mentioned in the [GType conventions][gtype-conventions], type names must
 * be at least three characters long. There is no upper length limit. The first
 * character must be a letter (a–z or A–Z) or an underscore (‘_’). Subsequent
 * characters can be letters, numbers or any of ‘-_+’.
 */


/* NOTE: some functions (some internal variants and exported ones)
 * invalidate data portions of the TypeNodes. if external functions/callbacks
 * are called, pointers to memory maintained by TypeNodes have to be looked up
 * again. this affects most of the struct TypeNode fields, e.g. ->children or
 * CLASSED_NODE_IFACES_ENTRIES() respectively IFACE_NODE_PREREQUISITES() (but
 * not ->supers[]), as all those memory portions can get realloc()ed during
 * callback invocation.
 *
 * LOCKING:
 * lock handling issues when calling static functions are indicated by
 * uppercase letter postfixes, all static functions have to have
 * one of the below postfixes:
 * - _I:	[Indifferent about locking]
 *   function doesn't care about locks at all
 * - _U:	[Unlocked invocation]
 *   no read or write lock has to be held across function invocation
 *   (locks may be acquired and released during invocation though)
 * - _L:	[Locked invocation]
 *   a write lock or more than 0 read locks have to be held across
 *   function invocation
 * - _W:	[Write-locked invocation]
 *   a write lock has to be held across function invocation
 * - _Wm:	[Write-locked invocation, mutatable]
 *   like _W, but the write lock might be released and reacquired
 *   during invocation, watch your pointers
 * - _WmREC:    [Write-locked invocation, mutatable, recursive]
 *   like _Wm, but also acquires recursive mutex class_init_rec_mutex
 */

#ifdef LOCK_DEBUG
#define G_READ_LOCK(rw_lock)    do { g_printerr (G_STRLOC ": readL++\n"); g_rw_lock_reader_lock (rw_lock); } while (0)
#define G_READ_UNLOCK(rw_lock)  do { g_printerr (G_STRLOC ": readL--\n"); g_rw_lock_reader_unlock (rw_lock); } while (0)
#define G_WRITE_LOCK(rw_lock)   do { g_printerr (G_STRLOC ": writeL++\n"); g_rw_lock_writer_lock (rw_lock); } while (0)
#define G_WRITE_UNLOCK(rw_lock) do { g_printerr (G_STRLOC ": writeL--\n"); g_rw_lock_writer_unlock (rw_lock); } while (0)
#else
#define G_READ_LOCK(rw_lock)    g_rw_lock_reader_lock (rw_lock)
#define G_READ_UNLOCK(rw_lock)  g_rw_lock_reader_unlock (rw_lock)
#define G_WRITE_LOCK(rw_lock)   g_rw_lock_writer_lock (rw_lock)
#define G_WRITE_UNLOCK(rw_lock) g_rw_lock_writer_unlock (rw_lock)
#endif
#define	INVALID_RECURSION(func, arg, type_name) G_STMT_START{ \
    static const gchar _action[] = " invalidly modified type ";  \
    gpointer _arg = (gpointer) (arg); const gchar *_tname = (type_name), *_fname = (func); \
    if (_arg) \
      g_error ("%s(%p)%s'%s'", _fname, _arg, _action, _tname); \
    else \
      g_error ("%s()%s'%s'", _fname, _action, _tname); \
}G_STMT_END
#define g_assert_type_system_initialized() \
  g_assert (static_quark_type_flags)

#define TYPE_FUNDAMENTAL_FLAG_MASK (G_TYPE_FLAG_CLASSED | \
				    G_TYPE_FLAG_INSTANTIATABLE | \
				    G_TYPE_FLAG_DERIVABLE | \
				    G_TYPE_FLAG_DEEP_DERIVABLE)
#define	TYPE_FLAG_MASK		   (G_TYPE_FLAG_ABSTRACT | G_TYPE_FLAG_VALUE_ABSTRACT | G_TYPE_FLAG_FINAL)
#define	SIZEOF_FUNDAMENTAL_INFO	   ((gssize) MAX (MAX (sizeof (GTypeFundamentalInfo), \
						       sizeof (gpointer)), \
                                                  sizeof (glong)))

/* The 2*sizeof(size_t) alignment here is borrowed from
 * GNU libc, so it should be good most everywhere.
 * It is more conservative than is needed on some 64-bit
 * platforms, but ia64 does require a 16-byte alignment.
 * The SIMD extensions for x86 and ppc32 would want a
 * larger alignment than this, but we don't need to
 * do better than malloc.
 */
#define STRUCT_ALIGNMENT (2 * sizeof (gsize))
#define ALIGN_STRUCT(offset) \
      ((offset + (STRUCT_ALIGNMENT - 1)) & -STRUCT_ALIGNMENT)


/* --- typedefs --- */
typedef struct _TypeNode        TypeNode;
typedef struct _CommonData      CommonData;
typedef struct _BoxedData       BoxedData;
typedef struct _IFaceData       IFaceData;
typedef struct _ClassData       ClassData;
typedef struct _InstanceData    InstanceData;
typedef union  _TypeData        TypeData;
typedef struct _IFaceEntries    IFaceEntries;
typedef struct _IFaceEntry      IFaceEntry;
typedef struct _IFaceHolder	IFaceHolder;


/* --- prototypes --- */
static inline GTypeFundamentalInfo*	type_node_fundamental_info_I	(TypeNode		*node);
static	      void			type_add_flags_W		(TypeNode		*node,
									 GTypeFlags		 flags);
static	      void			type_data_make_W		(TypeNode		*node,
									 const GTypeInfo	*info,
									 const GTypeValueTable	*value_table);
static inline void			type_data_ref_Wm		(TypeNode		*node);
static inline void			type_data_unref_U               (TypeNode		*node,
									 gboolean		 uncached);
static void				type_data_last_unref_Wm		(TypeNode *              node,
									 gboolean		 uncached);
static inline gpointer			type_get_qdata_L		(TypeNode		*node,
									 GQuark			 quark);
static inline void			type_set_qdata_W		(TypeNode		*node,
									 GQuark			 quark,
									 gpointer		 data);
static IFaceHolder*			type_iface_peek_holder_L	(TypeNode		*iface,
									 GType			 instance_type);
static gboolean                         type_iface_vtable_base_init_Wm  (TypeNode               *iface,
                                                                         TypeNode               *node);
static void                             type_iface_vtable_iface_init_Wm (TypeNode               *iface,
                                                                         TypeNode               *node);
static gboolean				type_node_is_a_L		(TypeNode		*node,
									 TypeNode		*iface_node);


/* --- enumeration --- */

/* The InitState enumeration is used to track the progress of initializing
 * both classes and interface vtables. Keeping the state of initialization
 * is necessary to handle new interfaces being added while we are initializing
 * the class or other interfaces.
 */
typedef enum
{
  UNINITIALIZED,
  BASE_CLASS_INIT,
  BASE_IFACE_INIT,
  CLASS_INIT,
  IFACE_INIT,
  INITIALIZED
} InitState;

/* --- structures --- */
struct _TypeNode
{
  guint        ref_count;  /* (atomic) */
#ifdef G_ENABLE_DEBUG
  guint        instance_count;  /* (atomic) */
#endif
  GTypePlugin *plugin;
  guint        n_children; /* writable with lock */
  guint        n_supers : 8;
  guint        n_prerequisites : 9;
  guint        is_classed : 1;
  guint        is_instantiatable : 1;
  guint        mutatable_check_cache : 1;	/* combines some common path checks */
  GType       *children; /* writable with lock */
  TypeData    *data;
  GQuark       qname;
  GData       *global_gdata;
  union {
    GAtomicArray iface_entries;		/* for !iface types */
    GAtomicArray offsets;
  } _prot;
  GType       *prerequisites;
  GType        supers[1]; /* flexible array */
};

#define SIZEOF_BASE_TYPE_NODE()			(G_STRUCT_OFFSET (TypeNode, supers))
#define MAX_N_SUPERS				(255)
#define MAX_N_CHILDREN				(G_MAXUINT)
#define	MAX_N_INTERFACES			(255) /* Limited by offsets being 8 bits */
#define	MAX_N_PREREQUISITES			(511)
#define NODE_TYPE(node)				(node->supers[0])
#define NODE_PARENT_TYPE(node)			(node->supers[1])
#define NODE_FUNDAMENTAL_TYPE(node)		(node->supers[node->n_supers])
#define NODE_NAME(node)				(g_quark_to_string (node->qname))
#define NODE_REFCOUNT(node)                     ((guint) g_atomic_int_get ((int *) &(node)->ref_count))
#define	NODE_IS_BOXED(node)			(NODE_FUNDAMENTAL_TYPE (node) == G_TYPE_BOXED)
#define	NODE_IS_IFACE(node)			(NODE_FUNDAMENTAL_TYPE (node) == G_TYPE_INTERFACE)
#define	CLASSED_NODE_IFACES_ENTRIES(node)	(&(node)->_prot.iface_entries)
#define	CLASSED_NODE_IFACES_ENTRIES_LOCKED(node)(G_ATOMIC_ARRAY_GET_LOCKED(CLASSED_NODE_IFACES_ENTRIES((node)), IFaceEntries))
#define	IFACE_NODE_N_PREREQUISITES(node)	((node)->n_prerequisites)
#define	IFACE_NODE_PREREQUISITES(node)		((node)->prerequisites)
#define	iface_node_get_holders_L(node)		((IFaceHolder*) type_get_qdata_L ((node), static_quark_iface_holder))
#define	iface_node_set_holders_W(node, holders)	(type_set_qdata_W ((node), static_quark_iface_holder, (holders)))
#define	iface_node_get_dependants_array_L(n)	((GType*) type_get_qdata_L ((n), static_quark_dependants_array))
#define	iface_node_set_dependants_array_W(n,d)	(type_set_qdata_W ((n), static_quark_dependants_array, (d)))
#define	TYPE_ID_MASK				((GType) ((1 << G_TYPE_FUNDAMENTAL_SHIFT) - 1))

#define NODE_IS_ANCESTOR(ancestor, node)                                                    \
        ((ancestor)->n_supers <= (node)->n_supers &&                                        \
	 (node)->supers[(node)->n_supers - (ancestor)->n_supers] == NODE_TYPE (ancestor))

struct _IFaceHolder
{
  GType           instance_type;
  GInterfaceInfo *info;
  GTypePlugin    *plugin;
  IFaceHolder    *next;
};

struct _IFaceEntry
{
  GType           iface_type;
  GTypeInterface *vtable;
  InitState       init_state;
};

struct _IFaceEntries {
  gsize offset_index;
  IFaceEntry entry[1];
};

#define IFACE_ENTRIES_HEADER_SIZE (sizeof(IFaceEntries) - sizeof(IFaceEntry))
#define IFACE_ENTRIES_N_ENTRIES(_entries) ( (G_ATOMIC_ARRAY_DATA_SIZE((_entries)) - IFACE_ENTRIES_HEADER_SIZE) / sizeof(IFaceEntry) )

struct _CommonData
{
  GTypeValueTable  *value_table;
};

struct _BoxedData
{
  CommonData         data;
  GBoxedCopyFunc     copy_func;
  GBoxedFreeFunc     free_func;
};

struct _IFaceData
{
  CommonData         common;
  guint16            vtable_size;
  GBaseInitFunc      vtable_init_base;
  GBaseFinalizeFunc  vtable_finalize_base;
  GClassInitFunc     dflt_init;
  GClassFinalizeFunc dflt_finalize;
  gconstpointer      dflt_data;
  gpointer           dflt_vtable;
};

struct _ClassData
{
  CommonData         common;
  guint16            class_size;
  guint16            class_private_size;
  int                init_state;  /* (atomic) - g_type_class_ref reads it unlocked */
  GBaseInitFunc      class_init_base;
  GBaseFinalizeFunc  class_finalize_base;
  GClassInitFunc     class_init;
  GClassFinalizeFunc class_finalize;
  gconstpointer      class_data;
  gpointer           class;
};

struct _InstanceData
{
  CommonData         common;
  guint16            class_size;
  guint16            class_private_size;
  int                init_state;  /* (atomic) - g_type_class_ref reads it unlocked */
  GBaseInitFunc      class_init_base;
  GBaseFinalizeFunc  class_finalize_base;
  GClassInitFunc     class_init;
  GClassFinalizeFunc class_finalize;
  gconstpointer      class_data;
  gpointer           class;
  guint16            instance_size;
  guint16            private_size;
  guint16            n_preallocs;
  GInstanceInitFunc  instance_init;
};

union _TypeData
{
  CommonData         common;
  BoxedData          boxed;
  IFaceData          iface;
  ClassData          class;
  InstanceData       instance;
};

typedef struct {
  gpointer            cache_data;
  GTypeClassCacheFunc cache_func;
} ClassCacheFunc;

typedef struct {
  gpointer                check_data;
  GTypeInterfaceCheckFunc check_func;
} IFaceCheckFunc;


/* --- variables --- */
static GRWLock         type_rw_lock;
static GRecMutex       class_init_rec_mutex;
static guint           static_n_class_cache_funcs = 0;
static ClassCacheFunc *static_class_cache_funcs = NULL;
static guint           static_n_iface_check_funcs = 0;
static IFaceCheckFunc *static_iface_check_funcs = NULL;
static GQuark          static_quark_type_flags = 0;
static GQuark          static_quark_iface_holder = 0;
static GQuark          static_quark_dependants_array = 0;
static guint           type_registration_serial = 0;

G_GNUC_BEGIN_IGNORE_DEPRECATIONS
GTypeDebugFlags	       _g_type_debug_flags = 0;
G_GNUC_END_IGNORE_DEPRECATIONS

/* --- type nodes --- */
static GHashTable       *static_type_nodes_ht = NULL;
static TypeNode		*static_fundamental_type_nodes[(G_TYPE_FUNDAMENTAL_MAX >> G_TYPE_FUNDAMENTAL_SHIFT) + 1] = { NULL, };
static GType		 static_fundamental_next = G_TYPE_RESERVED_USER_FIRST;

static inline TypeNode*
lookup_type_node_I (GType utype)
{
  if (utype > G_TYPE_FUNDAMENTAL_MAX)
    return (TypeNode*) (utype & ~TYPE_ID_MASK);
  else
    return static_fundamental_type_nodes[utype >> G_TYPE_FUNDAMENTAL_SHIFT];
}

/**
 * g_type_get_type_registration_serial:
 *
 * Returns an opaque serial number that represents the state of the set
 * of registered types. Any time a type is registered this serial changes,
 * which means you can cache information based on type lookups (such as
 * g_type_from_name()) and know if the cache is still valid at a later
 * time by comparing the current serial with the one at the type lookup.
 *
 * Since: 2.36
 *
 * Returns: An unsigned int, representing the state of type registrations
 */
guint
g_type_get_type_registration_serial (void)
{
  return (guint)g_atomic_int_get ((gint *)&type_registration_serial);
}

static TypeNode*
type_node_any_new_W (TypeNode             *pnode,
		     GType                 ftype,
		     const gchar          *name,
		     GTypePlugin          *plugin,
		     GTypeFundamentalFlags type_flags)
{
  guint n_supers;
  GType type;
  TypeNode *node;
  guint i, node_size = 0;

  n_supers = pnode ? pnode->n_supers + 1 : 0;
  
  if (!pnode)
    node_size += SIZEOF_FUNDAMENTAL_INFO;	      /* fundamental type info */
  node_size += SIZEOF_BASE_TYPE_NODE ();	      /* TypeNode structure */
  node_size += (sizeof (GType) * (1 + n_supers + 1)); /* self + ancestors + (0) for ->supers[] */
  node = g_malloc0 (node_size);
  if (!pnode)					      /* offset fundamental types */
    {
      node = G_STRUCT_MEMBER_P (node, SIZEOF_FUNDAMENTAL_INFO);
      static_fundamental_type_nodes[ftype >> G_TYPE_FUNDAMENTAL_SHIFT] = node;
      type = ftype;

#if ENABLE_VALGRIND
      VALGRIND_MALLOCLIKE_BLOCK (node, node_size - SIZEOF_FUNDAMENTAL_INFO, FALSE, TRUE);
#endif
    }
  else
    type = (GType) node;
  
  g_assert ((type & TYPE_ID_MASK) == 0);
  
  node->n_supers = n_supers;
  if (!pnode)
    {
      node->supers[0] = type;
      node->supers[1] = 0;
      
      node->is_classed = (type_flags & G_TYPE_FLAG_CLASSED) != 0;
      node->is_instantiatable = (type_flags & G_TYPE_FLAG_INSTANTIATABLE) != 0;
      
      if (NODE_IS_IFACE (node))
	{
          IFACE_NODE_N_PREREQUISITES (node) = 0;
	  IFACE_NODE_PREREQUISITES (node) = NULL;
	}
      else
	_g_atomic_array_init (CLASSED_NODE_IFACES_ENTRIES (node));
    }
  else
    {
      node->supers[0] = type;
      memcpy (node->supers + 1, pnode->supers, sizeof (GType) * (1 + pnode->n_supers + 1));
      
      node->is_classed = pnode->is_classed;
      node->is_instantiatable = pnode->is_instantiatable;
      
      if (NODE_IS_IFACE (node))
	{
	  IFACE_NODE_N_PREREQUISITES (node) = 0;
	  IFACE_NODE_PREREQUISITES (node) = NULL;
	}
      else
	{
	  guint j;
	  IFaceEntries *entries;

	  entries = _g_atomic_array_copy (CLASSED_NODE_IFACES_ENTRIES (pnode),
					  IFACE_ENTRIES_HEADER_SIZE,
					  0);
	  if (entries)
	    {
	      for (j = 0; j < IFACE_ENTRIES_N_ENTRIES (entries); j++)
		{
		  entries->entry[j].vtable = NULL;
		  entries->entry[j].init_state = UNINITIALIZED;
		}
	      _g_atomic_array_update (CLASSED_NODE_IFACES_ENTRIES (node),
				      entries);
	    }
	}

      i = pnode->n_children++;
      pnode->children = g_renew (GType, pnode->children, pnode->n_children);
      pnode->children[i] = type;
    }

  TRACE(GOBJECT_TYPE_NEW(name, node->supers[1], type));

  node->plugin = plugin;
  node->n_children = 0;
  node->children = NULL;
  node->data = NULL;
  node->qname = g_quark_from_string (name);
  node->global_gdata = NULL;
  g_hash_table_insert (static_type_nodes_ht,
		       (gpointer) g_quark_to_string (node->qname),
		       (gpointer) type);

  g_atomic_int_inc ((gint *)&type_registration_serial);

  return node;
}

static inline GTypeFundamentalInfo*
type_node_fundamental_info_I (TypeNode *node)
{
  GType ftype = NODE_FUNDAMENTAL_TYPE (node);
  
  if (ftype != NODE_TYPE (node))
    node = lookup_type_node_I (ftype);
  
  return node ? G_STRUCT_MEMBER_P (node, -SIZEOF_FUNDAMENTAL_INFO) : NULL;
}

static TypeNode*
type_node_fundamental_new_W (GType                 ftype,
			     const gchar          *name,
			     GTypeFundamentalFlags type_flags)
{
  GTypeFundamentalInfo *finfo;
  TypeNode *node;
  
  g_assert ((ftype & TYPE_ID_MASK) == 0);
  g_assert (ftype <= G_TYPE_FUNDAMENTAL_MAX);
  
  if (ftype >> G_TYPE_FUNDAMENTAL_SHIFT == static_fundamental_next)
    static_fundamental_next++;
  
  type_flags &= TYPE_FUNDAMENTAL_FLAG_MASK;
  
  node = type_node_any_new_W (NULL, ftype, name, NULL, type_flags);
  
  finfo = type_node_fundamental_info_I (node);
  finfo->type_flags = type_flags;
  
  return node;
}

static TypeNode*
type_node_new_W (TypeNode    *pnode,
		 const gchar *name,
		 GTypePlugin *plugin)
     
{
  g_assert (pnode);
  g_assert (pnode->n_supers < MAX_N_SUPERS);
  g_assert (pnode->n_children < MAX_N_CHILDREN);
  
  return type_node_any_new_W (pnode, NODE_FUNDAMENTAL_TYPE (pnode), name, plugin, 0);
}

static inline IFaceEntry*
lookup_iface_entry_I (IFaceEntries *entries,
                      TypeNode     *iface_node)
{
  guint8 *offsets;
  gsize offset_index;
  IFaceEntry *check;
  gsize index;
  IFaceEntry *entry;

  if (entries == NULL)
    return NULL;

  G_ATOMIC_ARRAY_DO_TRANSACTION
    (&iface_node->_prot.offsets, guint8,

     entry = NULL;
     offsets = transaction_data;
     offset_index = entries->offset_index;
     if (offsets != NULL &&
	 offset_index < G_ATOMIC_ARRAY_DATA_SIZE(offsets))
       {
	 index = offsets[offset_index];
	 if (index > 0)
	   {
	     /* zero means unset, subtract one to get real index */
	     index -= 1;

	     if (index < IFACE_ENTRIES_N_ENTRIES (entries))
	       {
		 check = (IFaceEntry *)&entries->entry[index];
		 if (check->iface_type == NODE_TYPE (iface_node))
		   entry = check;
	       }
	   }
       }
     );

 return entry;
}

static inline IFaceEntry*
type_lookup_iface_entry_L (TypeNode *node,
			   TypeNode *iface_node)
{
  if (!NODE_IS_IFACE (iface_node))
    return NULL;

  return lookup_iface_entry_I (CLASSED_NODE_IFACES_ENTRIES_LOCKED (node),
			       iface_node);
}


static inline gboolean
type_lookup_iface_vtable_I (TypeNode *node,
			    TypeNode *iface_node,
			    gpointer *vtable_ptr)
{
  IFaceEntry *entry;
  gboolean res;

  if (!NODE_IS_IFACE (iface_node))
    {
      if (vtable_ptr)
	*vtable_ptr = NULL;
      return FALSE;
    }

  G_ATOMIC_ARRAY_DO_TRANSACTION
    (CLASSED_NODE_IFACES_ENTRIES (node), IFaceEntries,

     entry = lookup_iface_entry_I (transaction_data, iface_node);
     res = entry != NULL;
     if (vtable_ptr)
       {
	 if (entry)
	   *vtable_ptr = entry->vtable;
	 else
	   *vtable_ptr = NULL;
       }
     );

  return res;
}

static inline gboolean
type_lookup_prerequisite_L (TypeNode *iface,
			    GType     prerequisite_type)
{
  if (NODE_IS_IFACE (iface) && IFACE_NODE_N_PREREQUISITES (iface))
    {
      GType *prerequisites = IFACE_NODE_PREREQUISITES (iface) - 1;
      guint n_prerequisites = IFACE_NODE_N_PREREQUISITES (iface);
      
      do
	{
	  guint i;
	  GType *check;
	  
	  i = (n_prerequisites + 1) >> 1;
	  check = prerequisites + i;
	  if (prerequisite_type == *check)
	    return TRUE;
	  else if (prerequisite_type > *check)
	    {
	      n_prerequisites -= i;
	      prerequisites = check;
	    }
	  else /* if (prerequisite_type < *check) */
	    n_prerequisites = i - 1;
	}
      while (n_prerequisites);
    }
  return FALSE;
}

static const gchar*
type_descriptive_name_I (GType type)
{
  if (type)
    {
      TypeNode *node = lookup_type_node_I (type);
      
      return node ? NODE_NAME (node) : "<unknown>";
    }
  else
    return "<invalid>";
}


/* --- type consistency checks --- */
static gboolean
check_plugin_U (GTypePlugin *plugin,
		gboolean     need_complete_type_info,
		gboolean     need_complete_interface_info,
		const gchar *type_name)
{
  /* G_IS_TYPE_PLUGIN() and G_TYPE_PLUGIN_GET_CLASS() are external calls: _U 
   */
  if (!plugin)
    {
      g_warning ("plugin handle for type '%s' is NULL",
		 type_name);
      return FALSE;
    }
  if (!G_IS_TYPE_PLUGIN (plugin))
    {
      g_warning ("plugin pointer (%p) for type '%s' is invalid",
		 plugin, type_name);
      return FALSE;
    }
  if (need_complete_type_info && !G_TYPE_PLUGIN_GET_CLASS (plugin)->complete_type_info)
    {
      g_warning ("plugin for type '%s' has no complete_type_info() implementation",
		 type_name);
      return FALSE;
    }
  if (need_complete_interface_info && !G_TYPE_PLUGIN_GET_CLASS (plugin)->complete_interface_info)
    {
      g_warning ("plugin for type '%s' has no complete_interface_info() implementation",
		 type_name);
      return FALSE;
    }
  return TRUE;
}

static gboolean
check_type_name_I (const gchar *type_name)
{
  static const gchar extra_chars[] = "-_+";
  const gchar *p = type_name;
  gboolean name_valid;
  
  if (!type_name[0] || !type_name[1] || !type_name[2])
    {
      g_warning ("type name '%s' is too short", type_name);
      return FALSE;
    }
  /* check the first letter */
  name_valid = (p[0] >= 'A' && p[0] <= 'Z') || (p[0] >= 'a' && p[0] <= 'z') || p[0] == '_';
  for (p = type_name + 1; *p; p++)
    name_valid &= ((p[0] >= 'A' && p[0] <= 'Z') ||
		   (p[0] >= 'a' && p[0] <= 'z') ||
		   (p[0] >= '0' && p[0] <= '9') ||
		   strchr (extra_chars, p[0]));
  if (!name_valid)
    {
      g_warning ("type name '%s' contains invalid characters", type_name);
      return FALSE;
    }
  if (g_type_from_name (type_name))
    {
      g_warning ("cannot register existing type '%s'", type_name);
      return FALSE;
    }
  
  return TRUE;
}

static gboolean
check_derivation_I (GType        parent_type,
		    const gchar *type_name)
{
  TypeNode *pnode;
  GTypeFundamentalInfo* finfo;
  
  pnode = lookup_type_node_I (parent_type);
  if (!pnode)
    {
      g_warning ("cannot derive type '%s' from invalid parent type '%s'",
		 type_name,
		 type_descriptive_name_I (parent_type));
      return FALSE;
    }
  finfo = type_node_fundamental_info_I (pnode);
  /* ensure flat derivability */
  if (!(finfo->type_flags & G_TYPE_FLAG_DERIVABLE))
    {
      g_warning ("cannot derive '%s' from non-derivable parent type '%s'",
		 type_name,
		 NODE_NAME (pnode));
      return FALSE;
    }
  /* ensure deep derivability */
  if (parent_type != NODE_FUNDAMENTAL_TYPE (pnode) &&
      !(finfo->type_flags & G_TYPE_FLAG_DEEP_DERIVABLE))
    {
      g_warning ("cannot derive '%s' from non-fundamental parent type '%s'",
		 type_name,
		 NODE_NAME (pnode));
      return FALSE;
    }
  if ((G_TYPE_FLAG_FINAL & GPOINTER_TO_UINT (type_get_qdata_L (pnode, static_quark_type_flags))) == G_TYPE_FLAG_FINAL)
    {
      g_warning ("cannot derive '%s' from final parent type '%s'",
                 type_name,
                 NODE_NAME (pnode));
      return FALSE;
    }
  
  return TRUE;
}

static gboolean
check_collect_format_I (const gchar *collect_format)
{
  const gchar *p = collect_format;
  gchar valid_format[] = { G_VALUE_COLLECT_INT, G_VALUE_COLLECT_LONG,
			   G_VALUE_COLLECT_INT64, G_VALUE_COLLECT_DOUBLE,
			   G_VALUE_COLLECT_POINTER, 0 };
  
  while (*p)
    if (!strchr (valid_format, *p++))
      return FALSE;
  return p - collect_format <= G_VALUE_COLLECT_FORMAT_MAX_LENGTH;
}

static gboolean
check_value_table_I (const gchar           *type_name,
		     const GTypeValueTable *value_table)
{
  if (!value_table)
    return FALSE;
  else if (value_table->value_init == NULL)
    {
      if (value_table->value_free || value_table->value_copy ||
	  value_table->value_peek_pointer ||
	  value_table->collect_format || value_table->collect_value ||
	  value_table->lcopy_format || value_table->lcopy_value)
	g_warning ("cannot handle uninitializable values of type '%s'",
		   type_name);
      return FALSE;
    }
  else /* value_table->value_init != NULL */
    {
      if (!value_table->value_free)
	{
	  /* +++ optional +++
	   * g_warning ("missing 'value_free()' for type '%s'", type_name);
	   * return FALSE;
	   */
	}
      if (!value_table->value_copy)
	{
	  g_warning ("missing 'value_copy()' for type '%s'", type_name);
	  return FALSE;
	}
      if ((value_table->collect_format || value_table->collect_value) &&
	  (!value_table->collect_format || !value_table->collect_value))
	{
	  g_warning ("one of 'collect_format' and 'collect_value()' is unspecified for type '%s'",
		     type_name);
	  return FALSE;
	}
      if (value_table->collect_format && !check_collect_format_I (value_table->collect_format))
	{
	  g_warning ("the '%s' specification for type '%s' is too long or invalid",
		     "collect_format",
		     type_name);
	  return FALSE;
	}
      if ((value_table->lcopy_format || value_table->lcopy_value) &&
	  (!value_table->lcopy_format || !value_table->lcopy_value))
	{
	  g_warning ("one of 'lcopy_format' and 'lcopy_value()' is unspecified for type '%s'",
		     type_name);
	  return FALSE;
	}
      if (value_table->lcopy_format && !check_collect_format_I (value_table->lcopy_format))
	{
	  g_warning ("the '%s' specification for type '%s' is too long or invalid",
		     "lcopy_format",
		     type_name);
	  return FALSE;
	}
    }
  return TRUE;
}

static gboolean
check_type_info_I (TypeNode        *pnode,
		   GType            ftype,
		   const gchar     *type_name,
		   const GTypeInfo *info)
{
  GTypeFundamentalInfo *finfo = type_node_fundamental_info_I (lookup_type_node_I (ftype));
  gboolean is_interface = ftype == G_TYPE_INTERFACE;
  
  g_assert (ftype <= G_TYPE_FUNDAMENTAL_MAX && !(ftype & TYPE_ID_MASK));
  
  /* check instance members */
  if (!(finfo->type_flags & G_TYPE_FLAG_INSTANTIATABLE) &&
      (info->instance_size || info->n_preallocs || info->instance_init))
    {
      if (pnode)
	g_warning ("cannot instantiate '%s', derived from non-instantiatable parent type '%s'",
		   type_name,
		   NODE_NAME (pnode));
      else
	g_warning ("cannot instantiate '%s' as non-instantiatable fundamental",
		   type_name);
      return FALSE;
    }
  /* check class & interface members */
  if (!((finfo->type_flags & G_TYPE_FLAG_CLASSED) || is_interface) &&
      (info->class_init || info->class_finalize || info->class_data ||
       info->class_size || info->base_init || info->base_finalize))
    {
      if (pnode)
	g_warning ("cannot create class for '%s', derived from non-classed parent type '%s'",
		   type_name,
                   NODE_NAME (pnode));
      else
	g_warning ("cannot create class for '%s' as non-classed fundamental",
		   type_name);
      return FALSE;
    }
  /* check interface size */
  if (is_interface && info->class_size < sizeof (GTypeInterface))
    {
      g_warning ("specified interface size for type '%s' is smaller than 'GTypeInterface' size",
		 type_name);
      return FALSE;
    }
  /* check class size */
  if (finfo->type_flags & G_TYPE_FLAG_CLASSED)
    {
      if (info->class_size < sizeof (GTypeClass))
	{
	  g_warning ("specified class size for type '%s' is smaller than 'GTypeClass' size",
		     type_name);
	  return FALSE;
	}
      if (pnode && info->class_size < pnode->data->class.class_size)
	{
	  g_warning ("specified class size for type '%s' is smaller "
		     "than the parent type's '%s' class size",
		     type_name,
		     NODE_NAME (pnode));
	  return FALSE;
	}
    }
  /* check instance size */
  if (finfo->type_flags & G_TYPE_FLAG_INSTANTIATABLE)
    {
      if (info->instance_size < sizeof (GTypeInstance))
	{
	  g_warning ("specified instance size for type '%s' is smaller than 'GTypeInstance' size",
		     type_name);
	  return FALSE;
	}
      if (pnode && info->instance_size < pnode->data->instance.instance_size)
	{
	  g_warning ("specified instance size for type '%s' is smaller "
		     "than the parent type's '%s' instance size",
		     type_name,
		     NODE_NAME (pnode));
	  return FALSE;
	}
    }
  
  return TRUE;
}

static TypeNode*
find_conforming_child_type_L (TypeNode *pnode,
			      TypeNode *iface)
{
  TypeNode *node = NULL;
  guint i;
  
  if (type_lookup_iface_entry_L (pnode, iface))
    return pnode;
  
  for (i = 0; i < pnode->n_children && !node; i++)
    node = find_conforming_child_type_L (lookup_type_node_I (pnode->children[i]), iface);
  
  return node;
}

static gboolean
check_add_interface_L (GType instance_type,
		       GType iface_type)
{