/**********************************************************************

  objspace.c - ObjectSpace extender for MRI.

  $Author$
  created at: Wed Jun 17 07:39:17 2009

  NOTE: This extension library is only expected to exist with C Ruby.

  All the files in this distribution are covered under the Ruby's
  license (see the file COPYING).

**********************************************************************/

#include "internal.h"
#include "internal/class.h"
#include "internal/compilers.h"
#include "internal/gc.h"
#include "internal/hash.h"
#include "internal/imemo.h"
#include "internal/sanitizers.h"
#include "ruby/io.h"
#include "ruby/re.h"
#include "ruby/st.h"
#include "symbol.h"

#undef rb_funcall

#include "ruby/ruby.h"

/*
 *  call-seq:
 *    ObjectSpace.memsize_of(obj) -> Integer
 *
 *  Return consuming memory size of obj in bytes.
 *
 *  Note that the return size is incomplete.  You need to deal with this
 *  information as only a *HINT*. Especially, the size of +T_DATA+ may not be
 *  correct.
 *
 *  This method is only expected to work with CRuby.
 *
 *  From Ruby 3.2 with Variable Width Allocation, it returns the actual slot
 *  size used plus any additional memory allocated outside the slot (such
 *  as external strings, arrays, or hash tables).
 */

static VALUE
memsize_of_m(VALUE self, VALUE obj)
{
    return SIZET2NUM(rb_obj_memsize_of(obj));
}

struct total_data {
    size_t total;
    VALUE klass;
};

static void
total_i(VALUE v, void *ptr)
{
    struct total_data *data = (struct total_data *)ptr;

    if (!rb_objspace_internal_object_p(v)) {
        if (data->klass == 0 || rb_obj_is_kind_of(v, data->klass)) {
            data->total += rb_obj_memsize_of(v);
        }
    }
}

typedef void (*each_obj_with_flags)(VALUE, void*);

struct obj_itr {
    each_obj_with_flags cb;
    void *data;
};

static int
heap_iter(void *vstart, void *vend, size_t stride, void *ptr)
{
    struct obj_itr * ctx = (struct obj_itr *)ptr;
    VALUE v;

    for (v = (VALUE)vstart; v != (VALUE)vend; v += stride) {
        void *poisoned = rb_asan_poisoned_object_p(v);
        rb_asan_unpoison_object(v, false);

        if (RBASIC(v)->flags) {
            (*ctx->cb)(v, ctx->data);
        }

        if (poisoned) {
            rb_asan_poison_object(v);
        }
    }

    return 0;
}

static void
each_object_with_flags(each_obj_with_flags cb, void *ctx)
{
    struct obj_itr data;
    data.cb = cb;
    data.data = ctx;
    rb_objspace_each_objects(heap_iter, &data);
}

/*
 *  call-seq:
 *    ObjectSpace.memsize_of_all(klass = nil) -> integer
 *
 *  Returns the total memory size of all living objects in bytes.
 *
 *    ObjectSpace.memsize_of_all # => 12502001
 *
 *  If +klass+ is given (which must be a Class or Module), returns the total
 *  memory size of objects whose class is, or is a subclass, of +klass+.
 *
 *    class MyClass; end
 *    ObjectSpace.memsize_of_all(MyClass) # => 0
 *    o = MyClass.new
 *    ObjectSpace.memsize_of_all(MyClass) # => 40
 *
 *  Note that the value returned may be an underestimate of the actual amount
 *  of memory used. Therefore, the value returned should only be used as a hint,
 *  rather than a source of truth. In particular, the size of +T_DATA+ objects may
 *  not be correct.
 *
 *  This method is only expected to work with C Ruby.
 */

static VALUE
memsize_of_all_m(int argc, VALUE *argv, VALUE self)
{
    struct total_data data = {0, 0};

    if (argc > 0) {
        rb_scan_args(argc, argv, "01", &data.klass);
        if (!NIL_P(data.klass)) rb_obj_is_kind_of(Qnil, data.klass);
    }

    each_object_with_flags(total_i, &data);
    return SIZET2NUM(data.total);
}

static int
set_zero_i(st_data_t key, st_data_t val, st_data_t arg)
{
    VALUE k = (VALUE)key;
    VALUE hash = (VALUE)arg;
    rb_hash_aset(hash, k, INT2FIX(0));
    return ST_CONTINUE;
}

static VALUE
setup_hash(int argc, VALUE *argv)
{
    VALUE hash;

    if (rb_scan_args(argc, argv, "01", &hash) == 1) {
        if (!RB_TYPE_P(hash, T_HASH))
            rb_raise(rb_eTypeError, "non-hash given");
    }

    if (hash == Qnil) {
        hash = rb_hash_new();
    }
    else if (!RHASH_EMPTY_P(hash)) {
        rb_hash_foreach(hash, set_zero_i, (st_data_t)hash);
    }

    return hash;
}

static void
cos_i(VALUE v, void *data)
{
    size_t *counts = (size_t *)data;
    counts[BUILTIN_TYPE(v)] += rb_obj_memsize_of(v);
}

static VALUE
type2sym(enum ruby_value_type i)
{
    VALUE type;
    switch (i) {
#define CASE_TYPE(t) case t: type = ID2SYM(rb_intern(#t)); break;
        CASE_TYPE(T_NONE);
        CASE_TYPE(T_OBJECT);
        CASE_TYPE(T_CLASS);
        CASE_TYPE(T_MODULE);
        CASE_TYPE(T_FLOAT);
        CASE_TYPE(T_STRING);
        CASE_TYPE(T_REGEXP);
        CASE_TYPE(T_ARRAY);
        CASE_TYPE(T_HASH);
        CASE_TYPE(T_STRUCT);
        CASE_TYPE(T_BIGNUM);
        CASE_TYPE(T_FILE);
        CASE_TYPE(T_DATA);
        CASE_TYPE(T_MATCH);
        CASE_TYPE(T_COMPLEX);
        CASE_TYPE(T_RATIONAL);
        CASE_TYPE(T_NIL);
        CASE_TYPE(T_TRUE);
        CASE_TYPE(T_FALSE);
        CASE_TYPE(T_SYMBOL);
        CASE_TYPE(T_FIXNUM);
        CASE_TYPE(T_UNDEF);
        CASE_TYPE(T_IMEMO);
        CASE_TYPE(T_NODE);
        CASE_TYPE(T_ICLASS);
        CASE_TYPE(T_MOVED);
        CASE_TYPE(T_ZOMBIE);
#undef CASE_TYPE
      default: rb_bug("type2sym: unknown type (%d)", i);
    }
    return type;
}

/*
 *  call-seq:
 *    ObjectSpace.count_objects_size([result_hash]) -> hash
 *
 *  Counts objects size (in bytes) for each type.
 *
 *  Note that this information is incomplete.  You need to deal with
 *  this information as only a *HINT*.  Especially, total size of
 *  T_DATA may be wrong.
 *
 *  It returns a hash as:
 *    {:TOTAL=>1461154, :T_CLASS=>158280, :T_MODULE=>20672, :T_STRING=>527249, ...}
 *
 *  If the optional argument, result_hash, is given,
 *  it is overwritten and returned.
 *  This is intended to avoid probe effect.
 *
 *  The contents of the returned hash is implementation defined.
 *  It may be changed in future.
 *
 *  This method is only expected to work with C Ruby.
 */

static VALUE
count_objects_size(int argc, VALUE *argv, VALUE os)
{
    size_t counts[T_MASK+1];
    size_t total = 0;
    enum ruby_value_type i;
    VALUE hash = setup_hash(argc, argv);

    for (i = 0; i <= T_MASK; i++) {
        counts[i] = 0;
    }

    each_object_with_flags(cos_i, &counts[0]);

    for (i = 0; i <= T_MASK; i++) {
        if (counts[i]) {
            VALUE type = type2sym(i);
            total += counts[i];
            rb_hash_aset(hash, type, SIZET2NUM(counts[i]));
        }
    }
    rb_hash_aset(hash, ID2SYM(rb_intern("TOTAL")), SIZET2NUM(total));
    return hash;
}

struct dynamic_symbol_counts {
    size_t mortal;
    size_t immortal;
};

static void
cs_i(VALUE v, void *n)
{
    struct dynamic_symbol_counts *counts = (struct dynamic_symbol_counts *)n;

    if (BUILTIN_TYPE(v) == T_SYMBOL) {
        ID id = RSYMBOL(v)->id;
        if ((id & ~ID_SCOPE_MASK) == 0) {
            counts->mortal++;
        }
        else {
            counts->immortal++;
        }
    }
}

size_t rb_sym_immortal_count(void);

/*
 *  call-seq:
 *     ObjectSpace.count_symbols(result_hash = nil) -> hash
 *
 *  Returns a hash containing the number of objects for each Symbol type.
 *
 *  The types of Symbols are the following:
 *
 *  - +mortal_dynamic_symbol+: Symbols that are garbage collectable.
 *  - +immortal_dynamic_symbol+: Symbols that are objects allocated from the
 *    garbage collector, but are not garbage collectable.
 *  - +immortal_static_symbol+: Symbols that are not allocated from the
 *    garbage collector, and are thus not garbage collectable.
 *  - +immortal_symbol+: the sum of +immortal_dynamic_symbol+ and +immortal_static_symbol+.
 *
 *  If the optional argument +result_hash+ is given, it is overwritten and
 *  returned. This is intended to avoid the probe effect.
 *
 *  This method is intended for developers interested in performance and memory
 *  usage of Ruby programs. The contents of the returned hash is implementation
 *  specific and may change in the future.
 *
 *  This method is only expected to work with C Ruby.
 */

static VALUE
count_symbols(int argc, VALUE *argv, VALUE os)
{
    struct dynamic_symbol_counts dynamic_counts = {0, 0};
    VALUE hash = setup_hash(argc, argv);

    size_t immortal_symbols = rb_sym_immortal_count();
    each_object_with_flags(cs_i, &dynamic_counts);

    rb_hash_aset(hash, ID2SYM(rb_intern("mortal_dynamic_symbol")),   SIZET2NUM(dynamic_counts.mortal));
    rb_hash_aset(hash, ID2SYM(rb_intern("immortal_dynamic_symbol")), SIZET2NUM(dynamic_counts.immortal));
    rb_hash_aset(hash, ID2SYM(rb_intern("immortal_static_symbol")),  SIZET2NUM(immortal_symbols - dynamic_counts.immortal));
    rb_hash_aset(hash, ID2SYM(rb_intern("immortal_symbol")),         SIZET2NUM(immortal_symbols));

    return hash;
}

static void
cto_i(VALUE v, void *data)
{
    VALUE hash = (VALUE)data;

    if (BUILTIN_TYPE(v) == T_DATA) {
        VALUE counter;
        VALUE key = RBASIC(v)->klass;

        if (key == 0) {
            const char *name = rb_objspace_data_type_name(v);
            if (name == 0) name = "unknown";
            key = ID2SYM(rb_intern(name));
        }

        counter = rb_hash_aref(hash, key);
        if (NIL_P(counter)) {
            counter = INT2FIX(1);
        }
        else {
            counter = INT2FIX(FIX2INT(counter) + 1);
        }

        rb_hash_aset(hash, key, counter);
    }
}

/*
 *  call-seq:
 *     ObjectSpace.count_tdata_objects(result_hash = nil) -> hash
 *
 *  Returns a hash containing the number of objects for each +T_DATA+ type.
 *  The keys are Class objects when the +T_DATA+ object has an associated class,
 *  or Symbol objects of the name defined in the +rb_data_type_struct+ for internal
 *  +T_DATA+ objects.
 *
 *    ObjectSpace.count_tdata_objects
 *    # => {RBS::Location => 39255, marshal_compat_table: 1, Encoding => 103, mutex: 1, ... }
 *
 *  If the optional argument +result_hash+ is given, it is overwritten and
 *  returned. This is intended to avoid the probe effect.
 *
 *  This method is intended for developers interested in performance and memory
 *  usage of Ruby programs. The contents of the returned hash is implementation
 *  specific and may change in the future.
 *
 *  This method is only expected to work with C Ruby.
 */

static VALUE
count_tdata_objects(int argc, VALUE *argv, VALUE self)
{
    VALUE hash = setup_hash(argc, argv);
    each_object_with_flags(cto_i, (void *)hash);
    return hash;
}

static ID imemo_type_ids[IMEMO_MASK+1];

static void
count_imemo_objects_i(VALUE v, void *data)
{
    VALUE hash = (VALUE)data;

    if (BUILTIN_TYPE(v) == T_IMEMO) {
        VALUE counter;
        VALUE key = ID2SYM(imemo_type_ids[imemo_type(v)]);

        counter = rb_hash_aref(hash, key);

        if (NIL_P(counter)) {
            counter = INT2FIX(1);
        }
        else {
            counter = INT2FIX(FIX2INT(counter) + 1);
        }

        rb_hash_aset(hash, key, counter);
    }
}

/*
 *  call-seq:
 *     ObjectSpace.count_imemo_objects(result_hash = nil) -> hash
 *
 *  Returns a hash containing the number of objects for each +T_IMEMO+ type.
 *  The keys are Symbol objects of the +T_IMEMO+ type name.
 *  +T_IMEMO+ objects are Ruby internal objects that are not visible to Ruby
 *  programs.
 *
 *    ObjectSpace.count_imemo_objects
 *    # => {imemo_callcache: 5482, imemo_constcache: 1258, imemo_ment: 13906, ... }
 *
 *  If the optional argument +result_hash+ is given, it is overwritten and
 *  returned. This is intended to avoid the probe effect.
 *
 *  This method is intended for developers interested in performance and memory
 *  usage of Ruby programs. The contents of the returned hash is implementation
 *  specific and may change in the future.
 *
 *  This method is only expected to work with C Ruby.
 */

static VALUE
count_imemo_objects(int argc, VALUE *argv, VALUE self)
{
    VALUE hash = setup_hash(argc, argv);

    if (imemo_type_ids[0] == 0) {
#define INIT_IMEMO_TYPE_ID(n) (imemo_type_ids[n] = rb_intern_const(#n))
        INIT_IMEMO_TYPE_ID(imemo_env);
        INIT_IMEMO_TYPE_ID(imemo_cref);
        INIT_IMEMO_TYPE_ID(imemo_svar);
        INIT_IMEMO_TYPE_ID(imemo_throw_data);
        INIT_IMEMO_TYPE_ID(imemo_ifunc);
        INIT_IMEMO_TYPE_ID(imemo_memo);
        INIT_IMEMO_TYPE_ID(imemo_ment);
        INIT_IMEMO_TYPE_ID(imemo_iseq);
        INIT_IMEMO_TYPE_ID(imemo_tmpbuf);
        INIT_IMEMO_TYPE_ID(imemo_callinfo);
        INIT_IMEMO_TYPE_ID(imemo_callcache);
        INIT_IMEMO_TYPE_ID(imemo_constcache);
        INIT_IMEMO_TYPE_ID(imemo_fields);
#undef INIT_IMEMO_TYPE_ID
    }

    each_object_with_flags(count_imemo_objects_i, (void *)hash);

    return hash;
}

static void
iow_mark(void *ptr)
{
    rb_gc_mark((VALUE)ptr);
}

static size_t
iow_size(const void *ptr)
{
    VALUE obj = (VALUE)ptr;
    return rb_obj_memsize_of(obj);
}

static const rb_data_type_t iow_data_type = {
    "ObjectSpace::InternalObjectWrapper",
    {iow_mark, 0, iow_size,},
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

static VALUE rb_cInternalObjectWrapper;

static VALUE
iow_newobj(VALUE obj)
{
    return TypedData_Wrap_Struct(rb_cInternalObjectWrapper, &iow_data_type, (void *)obj);
}

/* Returns the type of the internal object. */
static VALUE
iow_type(VALUE self)
{
    VALUE obj = (VALUE)DATA_PTR(self);
    return type2sym(BUILTIN_TYPE(obj));
}

/* See Object#inspect. */
static VALUE
iow_inspect(VALUE self)
{
    VALUE obj = (VALUE)DATA_PTR(self);
    VALUE type = type2sym(BUILTIN_TYPE(obj));

    return rb_sprintf("#<InternalObject:%p %"PRIsVALUE">", (void *)obj, rb_sym2str(type));
}

/* Returns the Object#object_id of the internal object. */
static VALUE
iow_internal_object_id(VALUE self)
{
    VALUE obj = (VALUE)DATA_PTR(self);
    return rb_obj_id(obj);
}

struct rof_data {
    VALUE refs;
    VALUE values;
};

static void
reachable_object_from_i(VALUE obj, void *data_ptr)
{
    struct rof_data *data = (struct rof_data *)data_ptr;
    VALUE key = obj;
    VALUE val = obj;

    if (!rb_objspace_garbage_object_p(obj)) {
        if (NIL_P(rb_hash_lookup(data->refs, key))) {
            rb_hash_aset(data->refs, key, Qtrue);

            if (rb_objspace_internal_object_p(obj)) {
                val = iow_newobj(obj);
            }

            rb_ary_push(data->values, val);
        }
    }
}

static int
collect_values(st_data_t key, st_data_t value, st_data_t data)
{
    VALUE ary = (VALUE)data;
    rb_ary_push(ary, (VALUE)value);
    return ST_CONTINUE;
}

/*
 *  call-seq:
 *     ObjectSpace.reachable_objects_from(obj) -> array or nil
 *
 *  [MRI specific feature] Return all reachable objects from `obj'.
 *
 *  This method returns all reachable objects from `obj'.
 *
 *  If `obj' has two or more references to the same object `x', then returned
 *  array only includes one `x' object.
 *
 *  If `obj' is a non-markable (non-heap management) object such as true,
 *  false, nil, symbols and Fixnums (and Flonum) then it simply returns nil.
 *
 *  If `obj' has references to an internal object, then it returns instances of
 *  ObjectSpace::InternalObjectWrapper class. This object contains a reference
 *  to an internal object and you can check the type of internal object with
 *  `type' method.
 *
 *  If `obj' is instance of ObjectSpace::InternalObjectWrapper class, then this
 *  method returns all reachable object from an internal object, which is
 *  pointed by `obj'.
 *
 *  With this method, you can find memory leaks.
 *
 *  This method is only expected to work with C Ruby.
 *
 *  Example:
 *    ObjectSpace.reachable_objects_from(['a', 'b', 'c'])
 *    #=> [Array, 'a', 'b', 'c']
 *
 *    ObjectSpace.reachable_objects_from(['a', 'a', 'a'])
 *    #=> [Array, 'a', 'a', 'a'] # all 'a' strings have different object id
 *
 *    ObjectSpace.reachable_objects_from([v = 'a', v, v])
 *    #=> [Array, 'a']
 *
 *    ObjectSpace.reachable_objects_from(1)
 *    #=> nil # 1 is not markable (heap managed) object
 *
 */

static VALUE
reachable_objects_from(VALUE self, VALUE obj)
{
    if (!RB_SPECIAL_CONST_P(obj)) {
        struct rof_data data;

        if (rb_typeddata_is_kind_of(obj, &iow_data_type)) {
            obj = (VALUE)DATA_PTR(obj);
        }

        data.refs = rb_obj_hide(rb_ident_hash_new());
        data.values = rb_ary_new();

        rb_objspace_reachable_objects_from(obj, reachable_object_from_i, &data);

        return data.values;
    }
    else {
        return Qnil;
    }
}

struct rofr_data {
    VALUE categories;
    const char *last_category;
    VALUE last_category_str;
    VALUE last_category_objects;
};

static void
reachable_object_from_root_i(const char *category, VALUE obj, void *ptr)
{
    struct rofr_data *data = (struct rofr_data *)ptr;
    VALUE category_str;
    VALUE category_objects;

    if (category == data->last_category) {
        category_str = data->last_category_str;
        category_objects = data->last_category_objects;
    }
    else {
        data->last_category = category;
        category_str = data->last_category_str = rb_str_new2(category);
        category_objects = data->last_category_objects = rb_ident_hash_new();
        if (!NIL_P(rb_hash_lookup(data->categories, category_str))) {
            rb_bug("reachable_object_from_root_i: category should insert at once");
        }
        rb_hash_aset(data->categories, category_str, category_objects);
    }

    if (!rb_objspace_garbage_object_p(obj) &&
        obj != data->categories &&
        obj != data->last_category_objects) {
        if (rb_objspace_internal_object_p(obj)) {
            obj = iow_newobj(obj);
        }
        rb_hash_aset(category_objects, obj, obj);
    }
}

static int
collect_values_of_values(VALUE category, VALUE category_objects, VALUE categories)
{
    VALUE ary = rb_ary_new();
    rb_hash_foreach(category_objects, collect_values, ary);
    rb_hash_aset(categories, category, ary);
    return ST_CONTINUE;
}

/*
 *  call-seq:
 *     ObjectSpace.reachable_objects_from_root -> hash
 *
 *  [MRI specific feature] Return all reachable objects from root.
 */
static VALUE
reachable_objects_from_root(VALUE self)
{
    struct rofr_data data;
    VALUE hash = data.categories = rb_ident_hash_new();
    data.last_category = 0;

    rb_objspace_reachable_objects_from_root(reachable_object_from_root_i, &data);
    rb_hash_foreach(hash, collect_values_of_values, hash);

    return hash;
}

static VALUE
wrap_klass_iow(VALUE klass)
{
    if (!RTEST(klass)) {
        return Qnil;
    }
    else if (RB_TYPE_P(klass, T_ICLASS) ||
             CLASS_OF(klass) == Qfalse /* hidden object */) {
        return iow_newobj(klass);
    }
    else {
        return klass;
    }
}

/*
 *  call-seq:
 *     ObjectSpace.internal_class_of(obj) -> Class or Module
 *
 *  [MRI specific feature] Return internal class of obj.
 *  obj can be an instance of InternalObjectWrapper.
 *
 *  Note that you should not use this method in your application.
 */
static VALUE
objspace_internal_class_of(VALUE self, VALUE obj)
{
    VALUE klass;

    if (rb_typeddata_is_kind_of(obj, &iow_data_type)) {
        obj = (VALUE)DATA_PTR(obj);
    }

    if (RB_TYPE_P(obj, T_IMEMO)) {
        return Qnil;
    }
    else {
        klass = CLASS_OF(obj);
        return wrap_klass_iow(klass);
    }
}

/*
 *  call-seq:
 *     ObjectSpace.internal_super_of(cls) -> Class or Module
 *
 *  [MRI specific feature] Return internal super class of cls (Class or Module).
 *  obj can be an instance of InternalObjectWrapper.
 *
 *  Note that you should not use this method in your application.
 */
static VALUE
objspace_internal_super_of(VALUE self, VALUE obj)
{
    VALUE super;

    if (rb_typeddata_is_kind_of(obj, &iow_data_type)) {
        obj = (VALUE)DATA_PTR(obj);
    }

    switch (OBJ_BUILTIN_TYPE(obj)) {
      case T_MODULE:
      case T_CLASS:
      case T_ICLASS:
        super = rb_class_super_of(obj);
        break;
      default:
        rb_raise(rb_eArgError, "class or module is expected");
    }

    return wrap_klass_iow(super);
}

void Init_object_tracing(VALUE rb_mObjSpace);
void Init_objspace_dump(VALUE rb_mObjSpace);

/*
 * Document-module: ObjectSpace
 *
 * The objspace library extends the ObjectSpace module and adds several
 * methods to get internal statistic information about
 * object/memory management.
 *
 * You need to <code>require 'objspace'</code> to use this extension module.
 *
 * Generally, you *SHOULD* *NOT* use this library if you do not know
 * about the MRI implementation.  Mainly, this library is for (memory)
 * profiler developers and MRI developers who need to know about MRI
 * memory usage.
 */

void
Init_objspace(void)
{
#undef rb_intern
    VALUE rb_mObjSpace;
#if 0
    rb_mObjSpace = rb_define_module("ObjectSpace"); /* let rdoc know */
#endif
    rb_mObjSpace = rb_const_get(rb_cObject, rb_intern("ObjectSpace"));

    rb_define_module_function(rb_mObjSpace, "memsize_of", memsize_of_m, 1);
    rb_define_module_function(rb_mObjSpace, "memsize_of_all", memsize_of_all_m, -1);

    rb_define_module_function(rb_mObjSpace, "count_objects_size", count_objects_size, -1);
    rb_define_module_function(rb_mObjSpace, "count_symbols", count_symbols, -1);
    rb_define_module_function(rb_mObjSpace, "count_tdata_objects", count_tdata_objects, -1);
    rb_define_module_function(rb_mObjSpace, "count_imemo_objects", count_imemo_objects, -1);

    rb_define_module_function(rb_mObjSpace, "reachable_objects_from", reachable_objects_from, 1);
    rb_define_module_function(rb_mObjSpace, "reachable_objects_from_root", reachable_objects_from_root, 0);

    rb_define_module_function(rb_mObjSpace, "internal_class_of", objspace_internal_class_of, 1);
    rb_define_module_function(rb_mObjSpace, "internal_super_of", objspace_internal_super_of, 1);

    /*
     * This class is used as a return value from
     * ObjectSpace::reachable_objects_from.
     *
     * When ObjectSpace::reachable_objects_from returns an object with
     * references to an internal object, an instance of this class is returned.
     *
     * You can use the #type method to check the type of the internal object.
     */
    rb_cInternalObjectWrapper = rb_define_class_under(rb_mObjSpace, "InternalObjectWrapper", rb_cObject);
    rb_undef_alloc_func(rb_cInternalObjectWrapper);
    rb_define_method(rb_cInternalObjectWrapper, "type", iow_type, 0);
    rb_define_method(rb_cInternalObjectWrapper, "inspect", iow_inspect, 0);
    rb_define_method(rb_cInternalObjectWrapper, "internal_object_id", iow_internal_object_id, 0);

    Init_object_tracing(rb_mObjSpace);
    Init_objspace_dump(rb_mObjSpace);
}