gc.c

/*
 * MacRuby implementation of Ruby 1.9's gc.c.
 *
 * This file is covered by the Ruby license. See COPYING for more details.
 *
 * Copyright (C) 2012, The MacRuby Team. All rights reserved.
 * Copyright (C) 2007-2011, Apple Inc. All rights reserved.
 * Copyright (C) 1993-2007 Yukihiro Matsumoto
 * Copyright (C) 2000 Network Applied Communication Laboratory, Inc.
 * Copyright (C) 2000 Information-technology Promotion Agency, Japan
 */

#include "ruby/config.h"

#if HAVE_AUTO_ZONE_H
# include <auto_zone.h>
#else
# include "auto_zone_1060.h"
#endif

#include "macruby_internal.h"
#include "ruby/signal.h"
#include "ruby/st.h"
#include "ruby/node.h"
#include "ruby/io.h"
#include "ruby/util.h"
#include "objc.h"
#include "vm.h"
#include "id.h"
#include "class.h"

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif

#include <mach/mach.h>

auto_zone_t *__auto_zone = NULL;

static VALUE nomem_error;

static bool dont_gc = false;
static bool stress_gc = false;

void
rb_memerror(void)
{
    rb_exc_raise(nomem_error);
}

static void
negative_size_allocation_error(const char *msg)
{
    rb_raise(rb_eNoMemError, "%s", msg);
}

/*
 *  call-seq:
 *    GC.stress                 => true or false
 *
 *  returns current status of GC stress mode.
 */

static VALUE
gc_stress_get(VALUE self, SEL sel)
{
    return stress_gc ? Qtrue : Qfalse;
}

/*
 *  call-seq:
 *    GC.stress = bool          => bool
 *
 *  updates GC stress mode.
 *
 *  When GC.stress = true, GC is invoked for all GC opportunity:
 *  all memory and object allocation.
 *
 *  Since it makes Ruby very slow, it is only for debugging.
 */

static VALUE
gc_stress_set(VALUE self, SEL sel, VALUE flag)
{
    rb_secure(2);
    stress_gc = RTEST(flag);
    return flag;
}

static int garbage_collect(void);

static void
rb_objc_no_gc_error(void)
{ 
    fprintf(stderr,
	    "The client that links against MacRuby was not built for "\
	    "GC. Please turn on garbage collection (-fobjc-gc) and "\
	    "try again.\n");
    exit(1);
}

static inline void *
ruby_xmalloc_memory(size_t size, int type)
{
    if ((ssize_t)size < 0) {
	negative_size_allocation_error("negative allocation size (or too big)");
    }
    if (size == 0) {
	size = 1;
    }

    if (__auto_zone == NULL) {
	rb_objc_no_gc_error();
    }

    if (stress_gc && !dont_gc) {
	garbage_collect();
    }

    void *mem = auto_zone_allocate_object(__auto_zone, size, type, 0, 0);
    if (mem == NULL) {
	rb_memerror();
    }
    return mem;
}

void *
ruby_xmalloc(size_t size)
{
    return ruby_xmalloc_memory(size, AUTO_MEMORY_SCANNED);
}

void *
ruby_xmalloc_ptrs(size_t size)
{
    int type;
//#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
//#define AUTO_POINTERS_ONLY (1 << 2)
//#define AUTO_MEMORY_ALL_POINTERS AUTO_POINTERS_ONLY
//
//    type = AUTO_MEMORY_ALL_POINTERS;
//#else
    type = AUTO_MEMORY_SCANNED;
//#endif
    return ruby_xmalloc_memory(size, type);
}

void *
ruby_xmalloc2(size_t n, size_t size)
{
    size_t len = size * n;
    if (n != 0 && size != len / n) {
	rb_raise(rb_eArgError, "malloc: possible integer overflow");
    }
    return ruby_xmalloc(len);
}

void *
ruby_xcalloc(size_t n, size_t size)
{
    void *mem = ruby_xmalloc2(n, size);
    memset(mem, 0, n * size);
    return mem;
}

void *
ruby_xrealloc(void *ptr, size_t size)
{
    if ((ssize_t)size < 0) {
	negative_size_allocation_error("negative re-allocation size");
    }
    if (ptr == NULL) {
	return ruby_xmalloc(size);
    }
    if (size == 0) {
	size = 1;
    }

    if (stress_gc && !dont_gc) {
	garbage_collect();
    }

    void *mem = malloc_zone_realloc(__auto_zone, ptr, size);
    if (mem == NULL) {
	rb_memerror();
    }
    return mem;
}

void *
ruby_xrealloc2(void *ptr, size_t n, size_t size)
{
    size_t len = size * n;
    if (n != 0 && size != len / n) {
	rb_raise(rb_eArgError, "realloc: possible integer overflow");
    }
    return ruby_xrealloc(ptr, len);
}

void
ruby_xfree(void *ptr)
{
    if (ptr != NULL) {
	auto_zone_retain(__auto_zone, ptr);
	malloc_zone_free(__auto_zone, ptr);
    }
}

/*
 *  call-seq:
 *     GC.enable    => true or false
 *
 *  Enables garbage collection, returning <code>true</code> if garbage
 *  collection was previously disabled.
 *
 *     GC.disable   #=> false
 *     GC.enable    #=> true
 *     GC.enable    #=> false
 *
 */

VALUE
rb_gc_enable(VALUE self, SEL sel)
{
    int old = dont_gc;

    auto_collector_reenable(__auto_zone);
    dont_gc = Qfalse;
    return old ? Qtrue : Qfalse;
}

/*
 *  call-seq:
 *     GC.disable    => true or false
 *
 *  Disables garbage collection, returning <code>true</code> if garbage
 *  collection was already disabled.
 *
 *     GC.disable   #=> false
 *     GC.disable   #=> true
 *
 */

VALUE
rb_gc_disable(VALUE self, SEL sel)
{
    int old = dont_gc;

    auto_collector_disable(__auto_zone);
    dont_gc = Qtrue;
    return old ? Qtrue : Qfalse;
}

VALUE rb_mGC;

void *
rb_gc_memmove(void *dst, const void *src, size_t len)
{
    return auto_zone_write_barrier_memmove(__auto_zone, dst, src, len);
}

void
rb_objc_set_associative_ref(void *obj, void *key, void *val)
{
    auto_zone_set_associative_ref(__auto_zone, obj, key, val);
}

void *
rb_objc_get_associative_ref(void *obj, void *key)
{
    return auto_zone_get_associative_ref(__auto_zone, obj, key);
}

const void *
rb_objc_retain_ni(const void *addr)
{
    return rb_objc_retain((void *)addr);
}

const void *
rb_objc_release_ni(const void *addr)
{
    return rb_objc_release((void *)addr);
}

void
rb_register_mark_object(VALUE obj)
{
    GC_RETAIN(obj);
}

void
rb_gc_unregister_address(VALUE *addr)
{
    /* TODO: implement me */
}

static void *__nsobject = NULL;

void *
rb_objc_newobj(size_t size)
{
    void *obj;

    if (stress_gc && !dont_gc) {
	garbage_collect();
    }

    obj = auto_zone_allocate_object(__auto_zone, size, AUTO_OBJECT_SCANNED,
	    0, 0);
    assert(obj != NULL);
    RBASIC(obj)->klass = (VALUE)__nsobject;
    return obj;
}

void
rb_objc_gc_register_thread(void)
{
    auto_zone_register_thread(__auto_zone);
}

void
rb_objc_gc_unregister_thread(void)
{
    auto_zone_unregister_thread(__auto_zone);
}

NODE*
rb_node_newnode(enum node_type type, VALUE a0, VALUE a1, VALUE a2)
{
    NODE *n = xmalloc(sizeof(struct RNode));

    n->flags |= T_NODE;
    nd_set_type(n, type);

    GC_WB(&n->u1.value, a0);
    GC_WB(&n->u2.value, a1);
    GC_WB(&n->u3.value, a2);

    // FIXME this retain is added because the parser is NOT GC-safe at this point
    GC_RETAIN(n);

    return n;
}

const char *ruby_node_name(int node);

void
rb_node_release(NODE *node)
{
    if (node == NULL || node == (NODE *)-1) {
	return;
    }

//    static int c = 0;
//    printf("%d RELEASE %s %p\n", ++c, ruby_node_name(nd_type(node)), node);

    switch (nd_type(node)) {
	case NODE_IF:		/* 1,2,3 */
	case NODE_FOR:
	case NODE_ITER:
	case NODE_WHEN:
	case NODE_MASGN:
	case NODE_RESCUE:
	case NODE_RESBODY:
	case NODE_CLASS:
	case NODE_BLOCK_PASS:
	    rb_node_release(node->u2.node);
	    /* fall through */
	case NODE_BLOCK:	/* 1,3 */
	case NODE_OPTBLOCK:
	case NODE_ARRAY:
	case NODE_ENSURE:
	case NODE_CALL:
	case NODE_DEFS:
	case NODE_OP_ASGN1:
	case NODE_ARGS:
	    rb_node_release(node->u1.node);
	    /* fall through */
	case NODE_SUPER:	/* 3 */
	case NODE_FCALL:
	case NODE_DEFN:
	case NODE_ARGS_AUX:
	    rb_node_release(node->u3.node);
	    break;

	case NODE_WHILE:	/* 1,2 */
	case NODE_UNTIL:
	case NODE_AND:
	case NODE_OR:
	case NODE_CASE:
	case NODE_SCLASS:
	case NODE_DOT2:
	case NODE_DOT3:
	case NODE_FLIP2:
	case NODE_FLIP3:
	case NODE_MATCH2:
	case NODE_MATCH3:
	case NODE_OP_ASGN_OR:
	case NODE_OP_ASGN_AND:
	case NODE_MODULE:
	case NODE_ARGSCAT:
	    rb_node_release(node->u1.node);
	    /* fall through */
	case NODE_FBODY:	/* 2 */
	case NODE_GASGN:
	case NODE_LASGN:
	case NODE_DASGN:
	case NODE_DASGN_CURR:
	case NODE_IASGN:
	case NODE_IASGN2:
	case NODE_CVASGN:
	case NODE_OPT_N:
	case NODE_EVSTR:
	case NODE_UNDEF:
	case NODE_POSTEXE:
	    rb_node_release(node->u2.node);
	    break;

	case NODE_HASH:	/* 1 */
	case NODE_DEFINED:
	case NODE_RETURN:
	case NODE_BREAK:
	case NODE_NEXT:
	case NODE_YIELD:
	case NODE_COLON2:
	case NODE_SPLAT:
	case NODE_TO_ARY:
	    rb_node_release(node->u1.node);
	    break;

	case NODE_SCOPE:	/* 2,3 */
	case NODE_CDECL:
	case NODE_OPT_ARG:
	    rb_node_release(node->u3.node);
	    rb_node_release(node->u2.node);
	    break;
    }

//    c--;

    // Some NODE structures are apparently reused somewhere in parserland.
    const int count = auto_zone_retain_count(__auto_zone, node);
    if (count > 0) {
	node->u1.node = node->u2.node = node->u3.node = NULL;
	GC_RELEASE(node);
    }
}

static void
rdata_finalize(void *rcv, SEL sel)
{
    if (RDATA(rcv)->dfree != NULL && RDATA(rcv)->data != NULL) {
	RDATA(rcv)->dfree(RDATA(rcv)->data);
	RDATA(rcv)->data = NULL;
    }
}

VALUE
rb_data_object_alloc(VALUE klass, void *datap, RUBY_DATA_FUNC dmark,
	RUBY_DATA_FUNC dfree)
{
    if (klass) {
	Check_Type(klass, T_CLASS);
    }

    NEWOBJ(data, struct RData);
    OBJSETUP(data, klass, T_DATA);
    GC_WB(&data->data, datap);
    data->dfree = dfree;
    data->dmark = dmark;

    if (dfree != NULL) {
	rb_objc_install_method2((Class)klass, "finalize", (IMP)rdata_finalize);
    }

    return (VALUE)data;
}

void
rb_gc_force_recycle(VALUE p)
{
    // FIXME this xfree call is commented because it's used by the parser which is NOT GC-safe at this point
//    xfree((void *)p);
}

static int
garbage_collect(void)
{
    if (!dont_gc) {
	objc_collect(OBJC_EXHAUSTIVE_COLLECTION);
    }
    return Qtrue;
}

void
rb_gc(void)
{
    garbage_collect();
}

/*
 *  call-seq:
 *     GC.start                     => nil
 *     gc.garbage_collect           => nil
 *     ObjectSpace.garbage_collect  => nil
 *
 *  Initiates garbage collection, unless manually disabled.
 *
 */

VALUE
rb_gc_start(VALUE self, SEL sel)
{
    rb_gc();
    return Qnil;
}

/*
 * Document-class: ObjectSpace
 *
 *  The <code>ObjectSpace</code> module contains a number of routines
 *  that interact with the garbage collection facility and allow you to
 *  traverse all living objects with an iterator.
 *
 *  <code>ObjectSpace</code> also provides support for object
 *  finalizers, procs that will be called when a specific object is
 *  about to be destroyed by garbage collection.
 *
 *     include ObjectSpace
 *
 *
 *     a = "A"
 *     b = "B"
 *     c = "C"
 *
 *
 *     define_finalizer(a, proc {|id| puts "Finalizer one on #{id}" })
 *     define_finalizer(a, proc {|id| puts "Finalizer two on #{id}" })
 *     define_finalizer(b, proc {|id| puts "Finalizer three on #{id}" })
 *
 *  <em>produces:</em>
 *
 *     Finalizer three on 537763470
 *     Finalizer one on 537763480
 *     Finalizer two on 537763480
 *
 */

struct rb_objc_recorder_context {
    VALUE class_of;
    int count;
    VALUE break_value;
};

static int
rb_objc_yield_classes(VALUE of)
{
    const int count = objc_getClassList(NULL, 0);
    assert(count > 0);

    Class *buf = (Class *)alloca(sizeof(Class) * count);
    objc_getClassList(buf, count);
    const bool only_modules = of == rb_cModule;

    int rcount = 0;
    for (int i = 0; i < count; i++) {
	Class k = buf[i];
	if (class_getName(k)[0] == '_') {
	    continue;
	}

	if (only_modules) {
	    if (!RCLASS_MODULE(k)) {
		continue;
	    }
	}
	else {
	    bool nsobject_based = false;
	    Class sk = k;
	    do {
		sk = (Class)RCLASS_SUPER(sk);
		if (sk == (Class)rb_cNSObject) {
		    nsobject_based = true;
		    break;
		}
	    }
	    while (sk != NULL);
	    if (!nsobject_based) {
		continue;
	    }
	}

	rb_yield((VALUE)k);
	RETURN_IF_BROKEN();
	rcount++;
    }

    return rcount;
}

static void 
rb_objc_recorder(task_t task, void *context, unsigned type_mask,
	vm_range_t *ranges, unsigned range_count)
{
    struct rb_objc_recorder_context *ctx;
    vm_range_t *r, *end;

    ctx = (struct rb_objc_recorder_context *)context;

    for (r = ranges, end = ranges + range_count; r < end; r++) {
	auto_memory_type_t type = auto_zone_get_layout_type(__auto_zone,
		(void *)r->address);
	if (type != AUTO_OBJECT_SCANNED && type != AUTO_OBJECT_UNSCANNED) {
	    continue;
	}
	if (*(Class *)r->address == NULL) {
	    continue;
	}
	if (ctx->class_of != 0) {
	    Class c;
	    bool ok = false;
	    for (c = *(Class *)r->address; c != NULL;
		 c = class_getSuperclass(c)) {
		if (c == (Class)ctx->class_of) {
		    ok = true;
		    break;
		}
	    }
	    if (!ok) {
		continue;
	    }
	}
	switch (TYPE(r->address)) {
	    case T_NONE: 
	    case T_NODE:
		continue;

	    case T_ICLASS: 
	    case T_CLASS:
	    case T_MODULE:
		rb_bug("object %p of type %d should not be recorded", 
		       (void *)r->address, TYPE(r->address));
	}
	rb_yield((VALUE)r->address);
	ctx->break_value = rb_vm_pop_broken_value();
	ctx->count++;
    }
}

/*
 *  call-seq:
 *     ObjectSpace.each_object([module]) {|obj| ... } => fixnum
 *
 *  Calls the block once for each living, nonimmediate object in this
 *  Ruby process. If <i>module</i> is specified, calls the block
 *  for only those classes or modules that match (or are a subclass of)
 *  <i>module</i>. Returns the number of objects found. Immediate
 *  objects (<code>Fixnum</code>s, <code>Symbol</code>s
 *  <code>true</code>, <code>false</code>, and <code>nil</code>) are
 *  never returned. In the example below, <code>each_object</code>
 *  returns both the numbers we defined and several constants defined in
 *  the <code>Math</code> module.
 *
 *     a = 102.7
 *     b = 95       # Won't be returned
 *     c = 12345678987654321
 *     count = ObjectSpace.each_object(Numeric) {|x| p x }
 *     puts "Total count: #{count}"
 *
 *  <em>produces:</em>
 *
 *     12345678987654321
 *     102.7
 *     2.71828182845905
 *     3.14159265358979
 *     2.22044604925031e-16
 *     1.7976931348623157e+308
 *     2.2250738585072e-308
 *     Total count: 7
 *
 */

static VALUE
os_each_obj(VALUE os, SEL sel, int argc, VALUE *argv)
{
    VALUE of;
    int count;

    rb_secure(4);
    if (argc == 0) {
	of = 0;
    }
    else {
	rb_scan_args(argc, argv, "01", &of);
    }
    RETURN_ENUMERATOR(os, 1, &of);

    /* Class/Module are a special case, because they are not auto objects */
    if (of == rb_cClass || of == rb_cModule) {
	count = rb_objc_yield_classes(of);
    }
    else {
	struct rb_objc_recorder_context ctx = {of, 0, Qundef};

	auto_collector_disable(__auto_zone);

	(((malloc_zone_t *)__auto_zone)->introspect->enumerator)(
	    mach_task_self(), (void *)&ctx, MALLOC_PTR_IN_USE_RANGE_TYPE,
	    (vm_address_t)__auto_zone, NULL, rb_objc_recorder);

	auto_collector_reenable(__auto_zone);

	if (ctx.break_value != Qundef) {
	    return ctx.break_value;
	}

	count = ctx.count;
    }

    return INT2FIX(count);
}

/*
 *  call-seq:
 *     ObjectSpace.undefine_finalizer(obj)
 *
 *  Removes all finalizers for <i>obj</i>.
 *
 */

static VALUE rb_cFinalizer;

static void *finalizer_key = NULL; // only used for its address

static IMP rb_objc_finalizer_finalize_super = NULL;

static void
rb_objc_finalizer_finalize(void *rcv, SEL sel)
{
    rb_vm_finalizer_t *f = (rb_vm_finalizer_t *)rcv;
    rb_vm_call_finalizer(f);
    rb_vm_unregister_finalizer(f); 
    if (rb_objc_finalizer_finalize_super != NULL) {
	((void(*)(void *, SEL))rb_objc_finalizer_finalize_super)(rcv, sel);
    }
}

static VALUE
undefine_final(VALUE os, SEL sel, VALUE obj)
{
    if (SPECIAL_CONST_P(obj)) {
	rb_raise(rb_eArgError, "immediate types are not finalizable");
    }
    rb_vm_finalizer_t *finalizer = rb_objc_get_associative_ref((void *)obj,
	    &finalizer_key);
    if (finalizer != NULL) {
	rb_ary_clear(finalizer->finalizers);
	rb_vm_unregister_finalizer(finalizer); 
	rb_objc_set_associative_ref((void *)obj, &finalizer_key, NULL);
    }
    return obj;
}

/*
 *  call-seq:
 *     ObjectSpace.define_finalizer(obj, aProc=proc())
 *
 *  Adds <i>aProc</i> as a finalizer, to be called after <i>obj</i>
 *  was destroyed.
 *
 */

static VALUE
define_final(VALUE os, SEL sel, int argc, VALUE *argv)
{
    VALUE obj, block;

    rb_scan_args(argc, argv, "11", &obj, &block);
    if (argc == 1) {
	block = rb_block_proc();
    }
    else if (!rb_respond_to(block, rb_intern("call"))) {
	rb_raise(rb_eArgError, "wrong type argument %s (should be callable)",
		rb_obj_classname(block));
    }

    if (SPECIAL_CONST_P(obj)) {
	rb_raise(rb_eArgError, "immediate types are not finalizable");
    }

    rb_vm_finalizer_t *finalizer = rb_objc_get_associative_ref((void *)obj,
	    &finalizer_key);
    if (finalizer == NULL) {
	finalizer = (rb_vm_finalizer_t *)
	    rb_objc_newobj(sizeof(rb_vm_finalizer_t *));
	finalizer->klass = rb_cFinalizer;
	finalizer->objid = rb_obj_id(obj, 0);
	GC_WB(&finalizer->finalizers, rb_ary_new());
	rb_objc_set_associative_ref((void *)obj, &finalizer_key, finalizer);
	rb_vm_register_finalizer(finalizer); 
    }

    rb_ary_push(finalizer->finalizers, block);
    
    // For RubySpec conformance.
    return rb_ary_new3(2, INT2FIX(rb_safe_level()), block);
}

void
rb_gc_copy_finalizer(VALUE dest, VALUE obj)
{
    // TODO
}

/*
 *  call-seq:
 *     ObjectSpace._id2ref(object_id) -> an_object
 *
 *  Converts an object id to a reference to the object. May not be
 *  called on an object id passed as a parameter to a finalizer.
 *
 *     s = "I am a string"                    #=> "I am a string"
 *     r = ObjectSpace._id2ref(s.object_id)   #=> "I am a string"
 *     r == s                                 #=> true
 *
 */

static VALUE
id2ref(VALUE obj, SEL sel, VALUE objid)
{
#if SIZEOF_LONG == SIZEOF_VOIDP
#define NUM2PTR(x) NUM2ULONG(x)
#elif SIZEOF_LONG_LONG == SIZEOF_VOIDP
#define NUM2PTR(x) NUM2ULL(x)
#endif
    VALUE ptr;
    void *p0;

    rb_secure(4);
    ptr = NUM2PTR(objid);
    p0 = (void *)ptr;

    if (ptr == Qtrue) return Qtrue;
    if (ptr == Qfalse) return Qfalse;
    if (ptr == Qnil) return Qnil;
    if (FIXNUM_P(ptr) || SYMBOL_P(ptr))
	return ptr;

    if (auto_zone_is_valid_pointer(__auto_zone, p0)) {
	auto_memory_type_t type = 
	    auto_zone_get_layout_type(__auto_zone, p0);
	if ((type == AUTO_OBJECT_SCANNED || type == AUTO_OBJECT_UNSCANNED)
	    && (NATIVE((VALUE)p0)
		|| (BUILTIN_TYPE(p0) < T_FIXNUM && BUILTIN_TYPE(p0) != T_ICLASS)))
	    return (VALUE)p0;
    }
    rb_raise(rb_eRangeError, "%p is not id value", p0);
}

/*
 *  Document-method: __id__
 *  Document-method: object_id
 *
 *  call-seq:
 *     obj.__id__       => fixnum
 *     obj.object_id    => fixnum
 *
 *  Returns an integer identifier for <i>obj</i>. The same number will
 *  be returned on all calls to <code>id</code> for a given object, and
 *  no two active objects will share an id.
 *  <code>Object#object_id</code> is a different concept from the
 *  <code>:name</code> notation, which returns the symbol id of
 *  <code>name</code>. Replaces the deprecated <code>Object#id</code>.
 */

/*
 *  call-seq:
 *     obj.hash    => fixnum
 *
 *  Generates a <code>Fixnum</code> hash value for this object. This
 *  function must have the property that <code>a.eql?(b)</code> implies
 *  <code>a.hash == b.hash</code>. The hash value is used by class
 *  <code>Hash</code>. Any hash value that exceeds the capacity of a
 *  <code>Fixnum</code> will be truncated before being used.
 */

VALUE
rb_obj_id(VALUE obj, SEL sel)
{
    return (VALUE)LONG2NUM((SIGNED_VALUE)obj);
}

/*
 *  call-seq:
 *     ObjectSpace.count_objects([result_hash]) -> hash
 *
 *  Counts objects for each type.
 *
 *  It returns a hash as:
 *  {:TOTAL=>10000, :FREE=>3011, :T_OBJECT=>6, :T_CLASS=>404, ...}
 *
 *  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 not expected to work except C Ruby.
 *
 */

static VALUE
count_objects(VALUE os, SEL sel, int argc, VALUE *argv)
{
    /* TODO implement me! */
    return rb_hash_new();
#if 0
    rb_objspace_t *objspace = &rb_objspace;
    size_t counts[T_MASK+1];
    size_t freed = 0;
    size_t total = 0;
    size_t i;
    VALUE hash;

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

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

    for (i = 0; i < heaps_used; i++) {
        RVALUE *p, *pend;

        p = heaps[i].slot; pend = p + heaps[i].limit;
        for (;p < pend; p++) {
            if (p->as.basic.flags) {
                counts[BUILTIN_TYPE(p)]++;
            }
            else {
                freed++;
            }
        }
        total += heaps[i].limit;
    }

    if (hash == Qnil)
        hash = rb_hash_new();
    rb_hash_aset(hash, ID2SYM(rb_intern("TOTAL")), SIZET2NUM(total));
    rb_hash_aset(hash, ID2SYM(rb_intern("FREE")), SIZET2NUM(freed));
    for (i = 0; i <= T_MASK; i++) {
        VALUE type;
        switch (i) {
#define COUNT_TYPE(t) case t: type = ID2SYM(rb_intern(#t)); break;
	    COUNT_TYPE(T_NONE);
	    COUNT_TYPE(T_OBJECT);
	    COUNT_TYPE(T_CLASS);
	    COUNT_TYPE(T_MODULE);
	    COUNT_TYPE(T_FLOAT);
	    COUNT_TYPE(T_STRING);
	    COUNT_TYPE(T_REGEXP);
	    COUNT_TYPE(T_ARRAY);
	    COUNT_TYPE(T_HASH);
	    COUNT_TYPE(T_STRUCT);
	    COUNT_TYPE(T_BIGNUM);
	    COUNT_TYPE(T_FILE);
	    COUNT_TYPE(T_DATA);
	    COUNT_TYPE(T_MATCH);
	    COUNT_TYPE(T_COMPLEX);
	    COUNT_TYPE(T_RATIONAL);
	    COUNT_TYPE(T_NIL);
	    COUNT_TYPE(T_TRUE);
	    COUNT_TYPE(T_FALSE);
	    COUNT_TYPE(T_SYMBOL);
	    COUNT_TYPE(T_FIXNUM);
	    COUNT_TYPE(T_VALUES);
	    COUNT_TYPE(T_UNDEF);
	    COUNT_TYPE(T_NODE);
	    COUNT_TYPE(T_ICLASS);
#undef COUNT_TYPE
          default:              type = INT2NUM(i); break;
        }
        if (counts[i])
            rb_hash_aset(hash, type, SIZET2NUM(counts[i]));
    }

    return hash;
#endif
}

/*
 *  call-seq:
 *     GC.count -> Integer
 *
 *  The number of times GC occured.
 *
 *  It returns the number of times GC occured since the process started.
 *
 */

#define gc_count rb_f_notimplement

/*
 *  The <code>GC</code> module provides an interface to Ruby's mark and
 *  sweep garbage collection mechanism. Some of the underlying methods
 *  are also available via the <code>ObjectSpace</code> module.
 */

static bool gc_disabled = false;

void
Init_PreGC(void)
{
    auto_collection_control_t *control;

#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
    __auto_zone = objc_collectableZone();
#else
    __auto_zone = auto_zone();
#endif
    
    if (__auto_zone == NULL) {
	rb_objc_no_gc_error();
    }

    __nsobject = (void *)objc_getClass("NSObject");

    control = auto_collection_parameters(__auto_zone);
    if (getenv("GC_DEBUG")) {
	control->log = AUTO_LOG_COLLECTIONS | AUTO_LOG_REGIONS | AUTO_LOG_UNUSUAL;
    }
    if (getenv("GC_DISABLE")) {
	gc_disabled = true;
	auto_collector_disable(__auto_zone);
    }
}

void
Init_PostGC(void)
{
    if (!gc_disabled) {
#if MAC_OS_X_VERSION_MAX_ALLOWED < 1070
	objc_startCollectorThread();
#endif
    }
}

void
Init_GC(void)
{
    VALUE rb_mObSpace;

    rb_mGC = rb_define_module("GC");
    rb_objc_define_module_function(rb_mGC, "start", rb_gc_start, 0);
    rb_objc_define_module_function(rb_mGC, "enable", rb_gc_enable, 0);
    rb_objc_define_module_function(rb_mGC, "disable", rb_gc_disable, 0);
    rb_objc_define_module_function(rb_mGC, "stress", gc_stress_get, 0);
    rb_objc_define_module_function(rb_mGC, "stress=", gc_stress_set, 1);
    rb_objc_define_module_function(rb_mGC, "count", gc_count, 0);
    rb_objc_define_method(rb_mGC, "garbage_collect", rb_gc_start, 0);

    rb_mObSpace = rb_define_module("ObjectSpace");
    rb_objc_define_module_function(rb_mObSpace, "each_object", os_each_obj, -1);
    rb_objc_define_module_function(rb_mObSpace, "garbage_collect", rb_gc_start, 0);

    rb_objc_define_module_function(rb_mObSpace, "define_finalizer", define_final, -1);
    rb_objc_define_module_function(rb_mObSpace, "undefine_finalizer", undefine_final, 1);

    rb_objc_define_module_function(rb_mObSpace, "_id2ref", id2ref, 1);

    nomem_error = rb_exc_new2(rb_eNoMemError, "failed to allocate memory");
    GC_RETAIN(nomem_error);

    rb_objc_define_method(rb_mKernel, "__id__", rb_obj_id, 0);
    rb_objc_define_method(rb_mKernel, "object_id", rb_obj_id, 0);

    rb_objc_define_module_function(rb_mObSpace, "count_objects", count_objects, -1);

    rb_cFinalizer = rb_define_class("__Finalizer", rb_cObject);
    rb_objc_finalizer_finalize_super =
	rb_objc_install_method2((Class)rb_cFinalizer,
		"finalize", (IMP)rb_objc_finalizer_finalize);
}

void
rb_global_variable(VALUE *slot)
{
    auto_zone_add_root(__auto_zone, (void *)slot, *(void **)slot);
}

void
rb_gc_register_address(VALUE *slot)
{
    rb_global_variable(slot);
}

static void 
print_memory_object(task_t task, void *context, unsigned type_mask,
	vm_range_t *ranges, unsigned range_count)
{
    const size_t min_size = *(size_t *)context;
    for (vm_range_t *r = ranges, *end = ranges + range_count; r < end; r++) {
	const size_t size = auto_zone_size(__auto_zone, (void *)r->address);
	if (size >= min_size) {
	    printf("address %p size %ld rc %d layout type ",
		    (void *)r->address, size,
		    auto_zone_retain_count(__auto_zone, (void *)r->address));
	    switch (auto_zone_get_layout_type(__auto_zone,
			(void *)r->address)) {
		case AUTO_OBJECT:
		    printf("object (class %s)\n",
			    class_getName(object_getClass((void *)r->address)));
		    break;
		default:
		    printf("memory\n");
		    break;
	    }
	}
    }
}

void
rb_print_memory_objects(size_t min_size)
{
    (((malloc_zone_t *)__auto_zone)->introspect->enumerator)(mach_task_self(),
	(void *)&min_size, MALLOC_PTR_IN_USE_RANGE_TYPE,
	(vm_address_t)__auto_zone, NULL, print_memory_object);
}