gc.c

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

  gc.c -

  $Author: nagachika $
  created at: Tue Oct  5 09:44:46 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

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

#include "ruby/ruby.h"
#include "ruby/st.h"
#include "ruby/re.h"
#include "ruby/io.h"
#include "ruby/thread.h"
#include "ruby/util.h"
#include "eval_intern.h"
#include "vm_core.h"
#include "internal.h"
#include "gc.h"
#include "constant.h"
#include "ruby_atomic.h"
#include "probes.h"
#include <stdio.h>
#include <setjmp.h>
#include <sys/types.h>
#include <assert.h>

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

#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
#if defined(__native_client__) && defined(NACL_NEWLIB)
# include "nacl/resource.h"
# undef HAVE_POSIX_MEMALIGN
# undef HAVE_MEMALIGN

#endif

#if defined _WIN32 || defined __CYGWIN__
#include <windows.h>
#elif defined(HAVE_POSIX_MEMALIGN)
#elif defined(HAVE_MEMALIGN)
#include <malloc.h>
#endif

#ifdef HAVE_VALGRIND_MEMCHECK_H
# include <valgrind/memcheck.h>
# ifndef VALGRIND_MAKE_MEM_DEFINED
#  define VALGRIND_MAKE_MEM_DEFINED(p, n) VALGRIND_MAKE_READABLE((p), (n))
# endif
# ifndef VALGRIND_MAKE_MEM_UNDEFINED
#  define VALGRIND_MAKE_MEM_UNDEFINED(p, n) VALGRIND_MAKE_WRITABLE((p), (n))
# endif
#else
# define VALGRIND_MAKE_MEM_DEFINED(p, n) 0
# define VALGRIND_MAKE_MEM_UNDEFINED(p, n) 0
#endif

#define rb_setjmp(env) RUBY_SETJMP(env)
#define rb_jmp_buf rb_jmpbuf_t

#ifndef GC_MALLOC_LIMIT
#define GC_MALLOC_LIMIT 8000000
#endif
#define HEAP_MIN_SLOTS 10000
#define FREE_MIN  4096

typedef struct {
    unsigned int initial_malloc_limit;
    unsigned int initial_heap_min_slots;
    unsigned int initial_free_min;
#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
    int gc_stress;
#endif
} ruby_gc_params_t;

static ruby_gc_params_t initial_params = {
    GC_MALLOC_LIMIT,
    HEAP_MIN_SLOTS,
    FREE_MIN,
#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
    FALSE,
#endif
};

#define nomem_error GET_VM()->special_exceptions[ruby_error_nomemory]

#ifndef GC_PROFILE_MORE_DETAIL
#define GC_PROFILE_MORE_DETAIL 0
#endif

typedef struct gc_profile_record {
    double gc_time;
    double gc_invoke_time;

    size_t heap_total_objects;
    size_t heap_use_size;
    size_t heap_total_size;

    int is_marked;

#if GC_PROFILE_MORE_DETAIL
    double gc_mark_time;
    double gc_sweep_time;

    size_t heap_use_slots;
    size_t heap_live_objects;
    size_t heap_free_objects;

    int have_finalize;

    size_t allocate_increase;
    size_t allocate_limit;
#endif
} gc_profile_record;

#if defined(_MSC_VER) || defined(__BORLANDC__) || defined(__CYGWIN__)
#pragma pack(push, 1) /* magic for reducing sizeof(RVALUE): 24 -> 20 */
#endif

typedef struct RVALUE {
    union {
        struct {
            VALUE flags;                /* always 0 for freed obj */
            struct RVALUE *next;
        } free;
        struct RBasic  basic;
        struct RObject object;
        struct RClass  klass;
        struct RFloat  flonum;
        struct RString string;
        struct RArray  array;
        struct RRegexp regexp;
        struct RHash   hash;
        struct RData   data;
        struct RTypedData   typeddata;
        struct RStruct rstruct;
        struct RBignum bignum;
        struct RFile   file;
        struct RNode   node;
        struct RMatch  match;
        struct RRational rational;
        struct RComplex complex;
    } as;
#ifdef GC_DEBUG
    const char *file;
    int   line;
#endif
} RVALUE;

#if defined(_MSC_VER) || defined(__BORLANDC__) || defined(__CYGWIN__)
#pragma pack(pop)
#endif

struct heaps_slot {
    struct heaps_header *header;
    uintptr_t *bits;
    RVALUE *freelist;
    struct heaps_slot *next;
    struct heaps_slot *prev;
    struct heaps_slot *free_next;
};

struct heaps_header {
    struct heaps_slot *base;
    uintptr_t *bits;
    RVALUE *start;
    RVALUE *end;
    size_t limit;
};

struct heaps_free_bitmap {
    struct heaps_free_bitmap *next;
};

struct gc_list {
    VALUE *varptr;
    struct gc_list *next;
};

#define STACK_CHUNK_SIZE 500

typedef struct stack_chunk {
    VALUE data[STACK_CHUNK_SIZE];
    struct stack_chunk *next;
} stack_chunk_t;

typedef struct mark_stack {
    stack_chunk_t *chunk;
    stack_chunk_t *cache;
    size_t index;
    size_t limit;
    size_t cache_size;
    size_t unused_cache_size;
} mark_stack_t;

#ifndef CALC_EXACT_MALLOC_SIZE
#define CALC_EXACT_MALLOC_SIZE 0
#endif

typedef struct rb_objspace {
    struct {
        size_t limit;
        size_t increase;
#if CALC_EXACT_MALLOC_SIZE
        size_t allocated_size;
        size_t allocations;
#endif
    } malloc_params;
    struct {
        size_t increment;
        struct heaps_slot *ptr;
        struct heaps_slot *sweep_slots;
        struct heaps_slot *free_slots;
        struct heaps_header **sorted;
        size_t length;
        size_t used;
        struct heaps_free_bitmap *free_bitmap;
        RVALUE *range[2];
        struct heaps_header *freed;
        size_t marked_num;
        size_t free_num;
        size_t free_min;
        size_t final_num;
        size_t do_heap_free;
    } heap;
    struct {
        int dont_gc;
        int dont_lazy_sweep;
        int during_gc;
        rb_atomic_t finalizing;
    } flags;
    struct {
        st_table *table;
        RVALUE *deferred;
    } final;
    mark_stack_t mark_stack;
    struct {
        int run;
        gc_profile_record *record;
        size_t count;
        size_t size;
        double invoke_time;
    } profile;
    struct gc_list *global_list;
    size_t count;
    size_t total_allocated_object_num;
    size_t total_freed_object_num;
    int gc_stress;

    struct mark_func_data_struct {
        void *data;
        void (*mark_func)(VALUE v, void *data);
    } *mark_func_data;
} rb_objspace_t;

#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
#define rb_objspace (*GET_VM()->objspace)
#define ruby_initial_gc_stress  initial_params.gc_stress
int *ruby_initial_gc_stress_ptr = &ruby_initial_gc_stress;
#else
static rb_objspace_t rb_objspace = {{GC_MALLOC_LIMIT}};
int *ruby_initial_gc_stress_ptr = &rb_objspace.gc_stress;
#endif
#define malloc_limit            objspace->malloc_params.limit
#define malloc_increase         objspace->malloc_params.increase
#define heaps                   objspace->heap.ptr
#define heaps_length            objspace->heap.length
#define heaps_used              objspace->heap.used
#define lomem                   objspace->heap.range[0]
#define himem                   objspace->heap.range[1]
#define heaps_inc               objspace->heap.increment
#define heaps_freed             objspace->heap.freed
#define dont_gc                 objspace->flags.dont_gc
#define during_gc               objspace->flags.during_gc
#define finalizing              objspace->flags.finalizing
#define finalizer_table         objspace->final.table
#define deferred_final_list     objspace->final.deferred
#define global_List             objspace->global_list
#define ruby_gc_stress          objspace->gc_stress
#define initial_malloc_limit    initial_params.initial_malloc_limit
#define initial_heap_min_slots  initial_params.initial_heap_min_slots
#define initial_free_min        initial_params.initial_free_min

#define is_lazy_sweeping(objspace) ((objspace)->heap.sweep_slots != 0)

#if SIZEOF_LONG == SIZEOF_VOIDP
# define nonspecial_obj_id(obj) (VALUE)((SIGNED_VALUE)(obj)|FIXNUM_FLAG)
# define obj_id_to_ref(objid) ((objid) ^ FIXNUM_FLAG) /* unset FIXNUM_FLAG */
#elif SIZEOF_LONG_LONG == SIZEOF_VOIDP
# define nonspecial_obj_id(obj) LL2NUM((SIGNED_VALUE)(obj) / 2)
# define obj_id_to_ref(objid) (FIXNUM_P(objid) ? \
   ((objid) ^ FIXNUM_FLAG) : (NUM2PTR(objid) << 1))
#else
# error not supported
#endif

#define RANY(o) ((RVALUE*)(o))
#define has_free_object (objspace->heap.free_slots && objspace->heap.free_slots->freelist)

#define HEAP_HEADER(p) ((struct heaps_header *)(p))
#define GET_HEAP_HEADER(x) (HEAP_HEADER((uintptr_t)(x) & ~(HEAP_ALIGN_MASK)))
#define GET_HEAP_SLOT(x) (GET_HEAP_HEADER(x)->base)
#define GET_HEAP_BITMAP(x) (GET_HEAP_HEADER(x)->bits)
#define NUM_IN_SLOT(p) (((uintptr_t)(p) & HEAP_ALIGN_MASK)/sizeof(RVALUE))
#define BITMAP_INDEX(p) (NUM_IN_SLOT(p) / (sizeof(uintptr_t) * CHAR_BIT))
#define BITMAP_OFFSET(p) (NUM_IN_SLOT(p) & ((sizeof(uintptr_t) * CHAR_BIT)-1))
#define MARKED_IN_BITMAP(bits, p) (bits[BITMAP_INDEX(p)] & ((uintptr_t)1 << BITMAP_OFFSET(p)))

#ifndef HEAP_ALIGN_LOG
/* default tiny heap size: 16KB */
#define HEAP_ALIGN_LOG 14
#endif

#define CEILDIV(i, mod) (((i) + (mod) - 1)/(mod))

enum {
    HEAP_ALIGN = (1UL << HEAP_ALIGN_LOG),
    HEAP_ALIGN_MASK = (~(~0UL << HEAP_ALIGN_LOG)),
    REQUIRED_SIZE_BY_MALLOC = (sizeof(size_t) * 5),
    HEAP_SIZE = (HEAP_ALIGN - REQUIRED_SIZE_BY_MALLOC),
    HEAP_OBJ_LIMIT = (unsigned int)((HEAP_SIZE - sizeof(struct heaps_header))/sizeof(struct RVALUE)),
    HEAP_BITMAP_LIMIT = CEILDIV(CEILDIV(HEAP_SIZE, sizeof(struct RVALUE)), sizeof(uintptr_t) * CHAR_BIT)
};

int ruby_gc_debug_indent = 0;
VALUE rb_mGC;
extern st_table *rb_class_tbl;
int ruby_disable_gc_stress = 0;

static void rb_objspace_call_finalizer(rb_objspace_t *objspace);
static VALUE define_final0(VALUE obj, VALUE block);
VALUE rb_define_final(VALUE obj, VALUE block);
VALUE rb_undefine_final(VALUE obj);
static void run_final(rb_objspace_t *objspace, VALUE obj);
static void initial_expand_heap(rb_objspace_t *objspace);

static void negative_size_allocation_error(const char *);
static void *aligned_malloc(size_t, size_t);
static void aligned_free(void *);

static void init_mark_stack(mark_stack_t *stack);

static VALUE lazy_sweep_enable(void);
static int garbage_collect(rb_objspace_t *);
static int gc_prepare_free_objects(rb_objspace_t *);
static void mark_tbl(rb_objspace_t *, st_table *);
static void rest_sweep(rb_objspace_t *);
static void gc_mark_stacked_objects(rb_objspace_t *);

static double getrusage_time(void);
static inline void gc_prof_timer_start(rb_objspace_t *);
static inline void gc_prof_timer_stop(rb_objspace_t *, int);
static inline void gc_prof_mark_timer_start(rb_objspace_t *);
static inline void gc_prof_mark_timer_stop(rb_objspace_t *);
static inline void gc_prof_sweep_timer_start(rb_objspace_t *);
static inline void gc_prof_sweep_timer_stop(rb_objspace_t *);
static inline void gc_prof_set_malloc_info(rb_objspace_t *);


/*
  --------------------------- ObjectSpace -----------------------------
*/

#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
rb_objspace_t *
rb_objspace_alloc(void)
{
    rb_objspace_t *objspace = malloc(sizeof(rb_objspace_t));
    memset(objspace, 0, sizeof(*objspace));
    malloc_limit = initial_malloc_limit;
    ruby_gc_stress = ruby_initial_gc_stress;

    return objspace;
}
#endif

#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
static void free_stack_chunks(mark_stack_t *);

void
rb_objspace_free(rb_objspace_t *objspace)
{
    rest_sweep(objspace);
    if (objspace->profile.record) {
        free(objspace->profile.record);
        objspace->profile.record = 0;
    }
    if (global_List) {
        struct gc_list *list, *next;
        for (list = global_List; list; list = next) {
            next = list->next;
            xfree(list);
        }
    }
    if (objspace->heap.free_bitmap) {
        struct heaps_free_bitmap *list, *next;
        for (list = objspace->heap.free_bitmap; list; list = next) {
            next = list->next;
            free(list);
        }
    }
    if (objspace->heap.sorted) {
        size_t i;
        for (i = 0; i < heaps_used; ++i) {
            free(objspace->heap.sorted[i]->bits);
            aligned_free(objspace->heap.sorted[i]);
        }
        free(objspace->heap.sorted);
        heaps_used = 0;
        heaps = 0;
    }
    free_stack_chunks(&objspace->mark_stack);
    free(objspace);
}
#endif

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

static void
allocate_sorted_heaps(rb_objspace_t *objspace, size_t next_heaps_length)
{
    struct heaps_header **p;
    struct heaps_free_bitmap *bits;
    size_t size, add, i;

    size = next_heaps_length*sizeof(struct heaps_header *);
    add = next_heaps_length - heaps_used;

    if (heaps_used > 0) {
        p = (struct heaps_header **)realloc(objspace->heap.sorted, size);
        if (p) objspace->heap.sorted = p;
    }
    else {
        p = objspace->heap.sorted = (struct heaps_header **)malloc(size);
    }

    if (p == 0) {
        during_gc = 0;
        rb_memerror();
    }

    for (i = 0; i < add; i++) {
        bits = (struct heaps_free_bitmap *)malloc(HEAP_BITMAP_LIMIT * sizeof(uintptr_t));
        if (bits == 0) {
            during_gc = 0;
            rb_memerror();
            return;
        }
        bits->next = objspace->heap.free_bitmap;
        objspace->heap.free_bitmap = bits;
    }
}

static void
link_free_heap_slot(rb_objspace_t *objspace, struct heaps_slot *slot)
{
    slot->free_next = objspace->heap.free_slots;
    objspace->heap.free_slots = slot;
}

static void
unlink_free_heap_slot(rb_objspace_t *objspace, struct heaps_slot *slot)
{
    objspace->heap.free_slots = slot->free_next;
    slot->free_next = NULL;
}

static void
assign_heap_slot(rb_objspace_t *objspace)
{
    RVALUE *p, *pend, *membase;
    struct heaps_slot *slot;
    size_t hi, lo, mid;
    size_t objs;

    objs = HEAP_OBJ_LIMIT;
    p = (RVALUE*)aligned_malloc(HEAP_ALIGN, HEAP_SIZE);
    if (p == 0) {
        during_gc = 0;
        rb_memerror();
    }
    slot = (struct heaps_slot *)malloc(sizeof(struct heaps_slot));
    if (slot == 0) {
       aligned_free(p);
       during_gc = 0;
       rb_memerror();
    }
    MEMZERO((void*)slot, struct heaps_slot, 1);

    slot->next = heaps;
    if (heaps) heaps->prev = slot;
    heaps = slot;

    membase = p;
    p = (RVALUE*)((VALUE)p + sizeof(struct heaps_header));
    if ((VALUE)p % sizeof(RVALUE) != 0) {
       p = (RVALUE*)((VALUE)p + sizeof(RVALUE) - ((VALUE)p % sizeof(RVALUE)));
       objs = (HEAP_SIZE - (size_t)((VALUE)p - (VALUE)membase))/sizeof(RVALUE);
    }

    lo = 0;
    hi = heaps_used;
    while (lo < hi) {
        register RVALUE *mid_membase;
        mid = (lo + hi) / 2;
        mid_membase = (RVALUE *)objspace->heap.sorted[mid];
        if (mid_membase < membase) {
            lo = mid + 1;
        }
        else if (mid_membase > membase) {
            hi = mid;
        }
        else {
            rb_bug("same heap slot is allocated: %p at %"PRIuVALUE, (void *)membase, (VALUE)mid);
        }
    }
    if (hi < heaps_used) {
        MEMMOVE(&objspace->heap.sorted[hi+1], &objspace->heap.sorted[hi], struct heaps_header*, heaps_used - hi);
    }
    heaps->header = (struct heaps_header *)membase;
    objspace->heap.sorted[hi] = heaps->header;
    objspace->heap.sorted[hi]->start = p;
    objspace->heap.sorted[hi]->end = (p + objs);
    objspace->heap.sorted[hi]->base = heaps;
    objspace->heap.sorted[hi]->limit = objs;
    assert(objspace->heap.free_bitmap != NULL);
    heaps->bits = (uintptr_t *)objspace->heap.free_bitmap;
    objspace->heap.sorted[hi]->bits = (uintptr_t *)objspace->heap.free_bitmap;
    objspace->heap.free_bitmap = objspace->heap.free_bitmap->next;
    memset(heaps->bits, 0, HEAP_BITMAP_LIMIT * sizeof(uintptr_t));
    pend = p + objs;
    if (lomem == 0 || lomem > p) lomem = p;
    if (himem < pend) himem = pend;
    heaps_used++;

    while (p < pend) {
        p->as.free.flags = 0;
        p->as.free.next = heaps->freelist;
        heaps->freelist = p;
        p++;
    }
    link_free_heap_slot(objspace, heaps);
}

static void
add_heap_slots(rb_objspace_t *objspace, size_t add)
{
    size_t i;
    size_t next_heaps_length;

    next_heaps_length = heaps_used + add;

    if (next_heaps_length > heaps_length) {
        allocate_sorted_heaps(objspace, next_heaps_length);
        heaps_length = next_heaps_length;
    }

    for (i = 0; i < add; i++) {
        assign_heap_slot(objspace);
    }
    heaps_inc = 0;
}

static void
init_heap(rb_objspace_t *objspace)
{
    add_heap_slots(objspace, HEAP_MIN_SLOTS / HEAP_OBJ_LIMIT);
    init_mark_stack(&objspace->mark_stack);

#ifdef USE_SIGALTSTACK
    {
        /* altstack of another threads are allocated in another place */
        rb_thread_t *th = GET_THREAD();
        void *tmp = th->altstack;
        th->altstack = malloc(rb_sigaltstack_size());
        free(tmp); /* free previously allocated area */
    }
#endif

    objspace->profile.invoke_time = getrusage_time();
    finalizer_table = st_init_numtable();
}

static void
initial_expand_heap(rb_objspace_t *objspace)
{
    size_t min_size = initial_heap_min_slots / HEAP_OBJ_LIMIT;

    if (min_size > heaps_used) {
        add_heap_slots(objspace, min_size - heaps_used);
    }
}

static void
set_heaps_increment(rb_objspace_t *objspace)
{
    size_t next_heaps_length = (size_t)(heaps_used * 1.8);

    if (next_heaps_length == heaps_used) {
        next_heaps_length++;
    }

    heaps_inc = next_heaps_length - heaps_used;

    if (next_heaps_length > heaps_length) {
        allocate_sorted_heaps(objspace, next_heaps_length);
        heaps_length = next_heaps_length;
    }
}

static int
heaps_increment(rb_objspace_t *objspace)
{
    if (heaps_inc > 0) {
        assign_heap_slot(objspace);
        heaps_inc--;
        return TRUE;
    }
    return FALSE;
}

static VALUE
newobj(VALUE klass, VALUE flags)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE obj;

    if (UNLIKELY(during_gc)) {
        dont_gc = 1;
        during_gc = 0;
        rb_bug("object allocation during garbage collection phase");
    }

    if (UNLIKELY(ruby_gc_stress && !ruby_disable_gc_stress)) {
        if (!garbage_collect(objspace)) {
            during_gc = 0;
            rb_memerror();
        }
    }

    if (UNLIKELY(!has_free_object)) {
        if (!gc_prepare_free_objects(objspace)) {
            during_gc = 0;
            rb_memerror();
        }
    }

    obj = (VALUE)objspace->heap.free_slots->freelist;
    objspace->heap.free_slots->freelist = RANY(obj)->as.free.next;
    if (objspace->heap.free_slots->freelist == NULL) {
        unlink_free_heap_slot(objspace, objspace->heap.free_slots);
    }

    MEMZERO((void*)obj, RVALUE, 1);
#ifdef GC_DEBUG
    RANY(obj)->file = rb_sourcefile();
    RANY(obj)->line = rb_sourceline();
#endif
    objspace->total_allocated_object_num++;

    return obj;
}

VALUE
rb_newobj(void)
{
    return newobj(0, T_NONE);
}

VALUE
rb_newobj_of(VALUE klass, VALUE flags)
{
    VALUE obj;

    obj = newobj(klass, flags);
    OBJSETUP(obj, klass, flags);

    return obj;
}

NODE*
rb_node_newnode(enum node_type type, VALUE a0, VALUE a1, VALUE a2)
{
    NODE *n = (NODE*)rb_newobj();

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

    n->u1.value = a0;
    n->u2.value = a1;
    n->u3.value = a2;

    return n;
}

VALUE
rb_data_object_alloc(VALUE klass, void *datap, RUBY_DATA_FUNC dmark, RUBY_DATA_FUNC dfree)
{
    NEWOBJ(data, struct RData);
    if (klass) Check_Type(klass, T_CLASS);
    OBJSETUP(data, klass, T_DATA);
    data->data = datap;
    data->dfree = dfree;
    data->dmark = dmark;

    return (VALUE)data;
}

VALUE
rb_data_typed_object_alloc(VALUE klass, void *datap, const rb_data_type_t *type)
{
    NEWOBJ(data, struct RTypedData);

    if (klass) Check_Type(klass, T_CLASS);

    OBJSETUP(data, klass, T_DATA);

    data->data = datap;
    data->typed_flag = 1;
    data->type = type;

    return (VALUE)data;
}

size_t
rb_objspace_data_type_memsize(VALUE obj)
{
    if (RTYPEDDATA_P(obj) && RTYPEDDATA_TYPE(obj)->function.dsize) {
        return RTYPEDDATA_TYPE(obj)->function.dsize(RTYPEDDATA_DATA(obj));
    }
    else {
        return 0;
    }
}

const char *
rb_objspace_data_type_name(VALUE obj)
{
    if (RTYPEDDATA_P(obj)) {
        return RTYPEDDATA_TYPE(obj)->wrap_struct_name;
    }
    else {
        return 0;
    }
}

static void gc_mark(rb_objspace_t *objspace, VALUE ptr);
static void gc_mark_children(rb_objspace_t *objspace, VALUE ptr);

static inline int
is_pointer_to_heap(rb_objspace_t *objspace, void *ptr)
{
    register RVALUE *p = RANY(ptr);
    register struct heaps_header *heap;
    register size_t hi, lo, mid;

    if (p < lomem || p > himem) return FALSE;
    if ((VALUE)p % sizeof(RVALUE) != 0) return FALSE;

    /* check if p looks like a pointer using bsearch*/
    lo = 0;
    hi = heaps_used;
    while (lo < hi) {
        mid = (lo + hi) / 2;
        heap = objspace->heap.sorted[mid];
        if (heap->start <= p) {
            if (p < heap->end)
                return TRUE;
            lo = mid + 1;
        }
        else {
            hi = mid;
        }
    }
    return FALSE;
}

static int
free_method_entry_i(ID key, rb_method_entry_t *me, st_data_t data)
{
    if (!me->mark) {
        rb_free_method_entry(me);
    }
    return ST_CONTINUE;
}

void
rb_free_m_table(st_table *tbl)
{
    st_foreach(tbl, free_method_entry_i, 0);
    st_free_table(tbl);
}

static int
free_const_entry_i(ID key, rb_const_entry_t *ce, st_data_t data)
{
    xfree(ce);
    return ST_CONTINUE;
}

void
rb_free_const_table(st_table *tbl)
{
    st_foreach(tbl, free_const_entry_i, 0);
    st_free_table(tbl);
}

static int obj_free(rb_objspace_t *, VALUE);

static inline struct heaps_slot *
add_slot_local_freelist(rb_objspace_t *objspace, RVALUE *p)
{
    struct heaps_slot *slot;

    (void)VALGRIND_MAKE_MEM_UNDEFINED((void*)p, sizeof(RVALUE));
    p->as.free.flags = 0;
    slot = GET_HEAP_SLOT(p);
    p->as.free.next = slot->freelist;
    slot->freelist = p;

    return slot;
}

static void
unlink_heap_slot(rb_objspace_t *objspace, struct heaps_slot *slot)
{
    if (slot->prev)
        slot->prev->next = slot->next;
    if (slot->next)
        slot->next->prev = slot->prev;
    if (heaps == slot)
        heaps = slot->next;
    if (objspace->heap.sweep_slots == slot)
        objspace->heap.sweep_slots = slot->next;
    slot->prev = NULL;
    slot->next = NULL;
}

static void
free_unused_heaps(rb_objspace_t *objspace)
{
    size_t i, j;
    struct heaps_header *last = 0;

    for (i = j = 1; j < heaps_used; i++) {
        if (objspace->heap.sorted[i]->limit == 0) {
            struct heaps_header* h = objspace->heap.sorted[i];
            ((struct heaps_free_bitmap *)(h->bits))->next =
                objspace->heap.free_bitmap;
            objspace->heap.free_bitmap = (struct heaps_free_bitmap *)h->bits;
            if (!last) {
                last = objspace->heap.sorted[i];
            }
            else {
                aligned_free(objspace->heap.sorted[i]);
            }
            heaps_used--;
        }
        else {
            if (i != j) {
                objspace->heap.sorted[j] = objspace->heap.sorted[i];
            }
            j++;
        }
    }
    if (last) {
        if (last < heaps_freed) {
            aligned_free(heaps_freed);
            heaps_freed = last;
        }
        else {
            aligned_free(last);
        }
    }
}
static inline void
make_deferred(RVALUE *p)
{
    p->as.basic.flags = (p->as.basic.flags & ~T_MASK) | T_ZOMBIE;
}

static inline void
make_io_deferred(RVALUE *p)
{
    rb_io_t *fptr = p->as.file.fptr;
    make_deferred(p);
    p->as.data.dfree = (void (*)(void*))rb_io_fptr_finalize;
    p->as.data.data = fptr;
}

static int
obj_free(rb_objspace_t *objspace, VALUE obj)
{
    switch (BUILTIN_TYPE(obj)) {
      case T_NIL:
      case T_FIXNUM:
      case T_TRUE:
      case T_FALSE:
        rb_bug("obj_free() called for broken object");
        break;
    }

    if (FL_TEST(obj, FL_EXIVAR)) {
        rb_free_generic_ivar((VALUE)obj);
        FL_UNSET(obj, FL_EXIVAR);
    }

    switch (BUILTIN_TYPE(obj)) {
      case T_OBJECT:
        if (!(RANY(obj)->as.basic.flags & ROBJECT_EMBED) &&
            RANY(obj)->as.object.as.heap.ivptr) {
            xfree(RANY(obj)->as.object.as.heap.ivptr);
        }
        break;
      case T_MODULE:
      case T_CLASS:
        rb_clear_cache_by_class((VALUE)obj);
        if (RCLASS_M_TBL(obj)) {
            rb_free_m_table(RCLASS_M_TBL(obj));
        }
        if (RCLASS_IV_TBL(obj)) {
            st_free_table(RCLASS_IV_TBL(obj));
        }
        if (RCLASS_CONST_TBL(obj)) {
            rb_free_const_table(RCLASS_CONST_TBL(obj));
        }
        if (RCLASS_IV_INDEX_TBL(obj)) {
            st_free_table(RCLASS_IV_INDEX_TBL(obj));
        }
        xfree(RANY(obj)->as.klass.ptr);
        break;
      case T_STRING:
        rb_str_free(obj);
        break;
      case T_ARRAY:
        rb_ary_free(obj);
        break;
      case T_HASH:
        if (RANY(obj)->as.hash.ntbl) {
            st_free_table(RANY(obj)->as.hash.ntbl);
        }
        break;
      case T_REGEXP:
        if (RANY(obj)->as.regexp.ptr) {
            onig_free(RANY(obj)->as.regexp.ptr);
        }
        break;
      case T_DATA:
        if (DATA_PTR(obj)) {
            if (RTYPEDDATA_P(obj)) {
                RDATA(obj)->dfree = RANY(obj)->as.typeddata.type->function.dfree;
            }
            if (RANY(obj)->as.data.dfree == (RUBY_DATA_FUNC)-1) {
                xfree(DATA_PTR(obj));
            }
            else if (RANY(obj)->as.data.dfree) {
                make_deferred(RANY(obj));
                return 1;
            }
        }
        break;
      case T_MATCH:
        if (RANY(obj)->as.match.rmatch) {
            struct rmatch *rm = RANY(obj)->as.match.rmatch;
            onig_region_free(&rm->regs, 0);
            if (rm->char_offset)
                xfree(rm->char_offset);
            xfree(rm);
        }
        break;
      case T_FILE:
        if (RANY(obj)->as.file.fptr) {
            make_io_deferred(RANY(obj));
            return 1;
        }
        break;
      case T_RATIONAL:
      case T_COMPLEX:
        break;
      case T_ICLASS:
        /* iClass shares table with the module */
        xfree(RANY(obj)->as.klass.ptr);
        break;

      case T_FLOAT:
        break;

      case T_BIGNUM:
        if (!(RBASIC(obj)->flags & RBIGNUM_EMBED_FLAG) && RBIGNUM_DIGITS(obj)) {
            xfree(RBIGNUM_DIGITS(obj));
        }
        break;
      case T_NODE:
        switch (nd_type(obj)) {
          case NODE_SCOPE:
            if (RANY(obj)->as.node.u1.tbl) {
                xfree(RANY(obj)->as.node.u1.tbl);
            }
            break;
          case NODE_ARGS:
            if (RANY(obj)->as.node.u3.args) {
                xfree(RANY(obj)->as.node.u3.args);
            }
            break;
          case NODE_ALLOCA:
            xfree(RANY(obj)->as.node.u1.node);
            break;
        }
        break;                  /* no need to free iv_tbl */

      case T_STRUCT:
        if ((RBASIC(obj)->flags & RSTRUCT_EMBED_LEN_MASK) == 0 &&
            RANY(obj)->as.rstruct.as.heap.ptr) {
            xfree(RANY(obj)->as.rstruct.as.heap.ptr);
        }
        break;

      default:
        rb_bug("gc_sweep(): unknown data type 0x%x(%p) 0x%"PRIxVALUE,
               BUILTIN_TYPE(obj), (void*)obj, RBASIC(obj)->flags);
    }

    return 0;
}

void
Init_heap(void)
{
    init_heap(&rb_objspace);
}

typedef int each_obj_callback(void *, void *, size_t, void *);

struct each_obj_args {
    each_obj_callback *callback;
    void *data;
};

static VALUE
objspace_each_objects(VALUE arg)
{
    size_t i;
    RVALUE *membase = 0;
    RVALUE *pstart, *pend;
    rb_objspace_t *objspace = &rb_objspace;
    struct each_obj_args *args = (struct each_obj_args *)arg;
    volatile VALUE v;

    i = 0;
    while (i < heaps_used) {
        while (0 < i && (uintptr_t)membase < (uintptr_t)objspace->heap.sorted[i-1])
            i--;
        while (i < heaps_used && (uintptr_t)objspace->heap.sorted[i] <= (uintptr_t)membase)
            i++;
        if (heaps_used <= i)
          break;
        membase = (RVALUE *)objspace->heap.sorted[i];

        pstart = objspace->heap.sorted[i]->start;
        pend = pstart + objspace->heap.sorted[i]->limit;

        for (; pstart != pend; pstart++) {
            if (pstart->as.basic.flags) {
                v = (VALUE)pstart; /* acquire to save this object */
                break;
            }
        }
        if (pstart != pend) {
            if ((*args->callback)(pstart, pend, sizeof(RVALUE), args->data)) {
                break;
            }
        }
    }
    RB_GC_GUARD(v);

    return Qnil;
}

/*
 * rb_objspace_each_objects() is special C API to walk through
 * Ruby object space.  This C API is too difficult to use it.
 * To be frank, you should not use it. Or you need to read the
 * source code of this function and understand what this function does.
 *
 * 'callback' will be called several times (the number of heap slot,
 * at current implementation) with:
 *   vstart: a pointer to the first living object of the heap_slot.
 *   vend: a pointer to next to the valid heap_slot area.
 *   stride: a distance to next VALUE.
 *
 * If callback() returns non-zero, the iteration will be stopped.
 *
 * This is a sample callback code to iterate liveness objects:
 *
 *   int
 *   sample_callback(void *vstart, void *vend, int stride, void *data) {
 *     VALUE v = (VALUE)vstart;
 *     for (; v != (VALUE)vend; v += stride) {
 *       if (RBASIC(v)->flags) { // liveness check
 *       // do something with live object 'v'
 *     }
 *     return 0; // continue to iteration
 *   }
 *
 * Note: 'vstart' is not a top of heap_slot.  This point the first
 *       living object to grasp at least one object to avoid GC issue.
 *       This means that you can not walk through all Ruby object slot
 *       including freed object slot.
 *
 * Note: On this implementation, 'stride' is same as sizeof(RVALUE).
 *       However, there are possibilities to pass variable values with
 *       'stride' with some reasons.  You must use stride instead of
 *       use some constant value in the iteration.
 */
void
rb_objspace_each_objects(each_obj_callback *callback, void *data)
{
    struct each_obj_args args;
    rb_objspace_t *objspace = &rb_objspace;

    rest_sweep(objspace);
    objspace->flags.dont_lazy_sweep = TRUE;

    args.callback = callback;
    args.data = data;
    rb_ensure(objspace_each_objects, (VALUE)&args, lazy_sweep_enable, Qnil);
}

struct os_each_struct {
    size_t num;
    VALUE of;
};

static int
internal_object_p(VALUE obj)
{
    RVALUE *p = (RVALUE *)obj;

    if (p->as.basic.flags) {
        switch (BUILTIN_TYPE(p)) {
          case T_NONE:
          case T_ICLASS:
          case T_NODE:
          case T_ZOMBIE:
            break;
          case T_CLASS:
            if (FL_TEST(p, FL_SINGLETON))
              break;
          default:
            if (!p->as.basic.klass) break;
            return 0;
        }
    }
    return 1;
}

int
rb_objspace_internal_object_p(VALUE obj)
{
    return internal_object_p(obj);
}

static int
os_obj_of_i(void *vstart, void *vend, size_t stride, void *data)
{
    struct os_each_struct *oes = (struct os_each_struct *)data;
    RVALUE *p = (RVALUE *)vstart, *pend = (RVALUE *)vend;

    for (; p != pend; p++) {
        volatile VALUE v = (VALUE)p;
        if (!internal_object_p(v)) {
            if (!oes->of || rb_obj_is_kind_of(v, oes->of)) {
                rb_yield(v);
                oes->num++;
            }
        }
    }

    return 0;
}

static VALUE
os_obj_of(VALUE of)
{
    struct os_each_struct oes;

    oes.num = 0;
    oes.of = of;
    rb_objspace_each_objects(os_obj_of_i, &oes);
    return SIZET2NUM(oes.num);
}

/*
 *  call-seq:
 *     ObjectSpace.each_object([module]) {|obj| ... } -> fixnum
 *     ObjectSpace.each_object([module])              -> an_enumerator
 *
 *  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.
 *
 *  If no block is given, an enumerator is returned instead.
 *
 *     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(int argc, VALUE *argv, VALUE os)
{
    VALUE of;

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

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

static VALUE
undefine_final(VALUE os, VALUE obj)
{
    return rb_undefine_final(obj);
}

VALUE
rb_undefine_final(VALUE obj)
{
    rb_objspace_t *objspace = &rb_objspace;
    st_data_t data = obj;
    rb_check_frozen(obj);
    st_delete(finalizer_table, &data, 0);
    FL_UNSET(obj, FL_FINALIZE);
    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(int argc, VALUE *argv, VALUE os)
{
    VALUE obj, block;

    rb_scan_args(argc, argv, "11", &obj, &block);
    rb_check_frozen(obj);
    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));
    }

    return define_final0(obj, block);
}

static VALUE
define_final0(VALUE obj, VALUE block)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE table;
    st_data_t data;

    if (!FL_ABLE(obj)) {
        rb_raise(rb_eArgError, "cannot define finalizer for %s",
                 rb_obj_classname(obj));
    }
    RBASIC(obj)->flags |= FL_FINALIZE;

    block = rb_ary_new3(2, INT2FIX(rb_safe_level()), block);
    OBJ_FREEZE(block);

    if (st_lookup(finalizer_table, obj, &data)) {
        table = (VALUE)data;
        rb_ary_push(table, block);
    }
    else {
        table = rb_ary_new3(1, block);
        RBASIC(table)->klass = 0;
        st_add_direct(finalizer_table, obj, table);
    }
    return block;
}

VALUE
rb_define_final(VALUE obj, VALUE block)
{
    rb_check_frozen(obj);
    if (!rb_respond_to(block, rb_intern("call"))) {
        rb_raise(rb_eArgError, "wrong type argument %s (should be callable)",
                 rb_obj_classname(block));
    }
    return define_final0(obj, block);
}

void
rb_gc_copy_finalizer(VALUE dest, VALUE obj)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE table;
    st_data_t data;

    if (!FL_TEST(obj, FL_FINALIZE)) return;
    if (st_lookup(finalizer_table, obj, &data)) {
        table = (VALUE)data;
        st_insert(finalizer_table, dest, table);
    }
    FL_SET(dest, FL_FINALIZE);
}

static VALUE
run_single_final(VALUE arg)
{
    VALUE *args = (VALUE *)arg;
    rb_eval_cmd(args[0], args[1], (int)args[2]);
    return Qnil;
}

static void
run_finalizer(rb_objspace_t *objspace, VALUE obj, VALUE table)
{
    long i;
    int status;
    VALUE args[3];
    VALUE objid = nonspecial_obj_id(obj);
    VALUE saved_errinfo = rb_errinfo();

    if (RARRAY_LEN(table) > 0) {
        args[1] = rb_obj_freeze(rb_ary_new3(1, objid));
    }
    else {
        args[1] = 0;
    }

    args[2] = (VALUE)rb_safe_level();
    rb_set_errinfo(Qnil);
    for (i=0; i<RARRAY_LEN(table); i++) {
        VALUE final = RARRAY_PTR(table)[i];
        args[0] = RARRAY_PTR(final)[1];
        args[2] = FIX2INT(RARRAY_PTR(final)[0]);
        status = 0;
        rb_protect(run_single_final, (VALUE)args, &status);
        if (status)
            rb_set_errinfo(Qnil);
    }
    GET_THREAD()->errinfo = saved_errinfo;
}

static void
run_final(rb_objspace_t *objspace, VALUE obj)
{
    RUBY_DATA_FUNC free_func = 0;
    st_data_t key, table;

    objspace->heap.final_num--;

    RBASIC(obj)->klass = 0;

    if (RTYPEDDATA_P(obj)) {
        free_func = RTYPEDDATA_TYPE(obj)->function.dfree;
    }
    else {
        free_func = RDATA(obj)->dfree;
    }
    if (free_func) {
        (*free_func)(DATA_PTR(obj));
    }

    key = (st_data_t)obj;
    if (st_delete(finalizer_table, &key, &table)) {
        run_finalizer(objspace, obj, (VALUE)table);
    }
}

static void
finalize_list(rb_objspace_t *objspace, RVALUE *p)
{
    while (p) {
        RVALUE *tmp = p->as.free.next;
        run_final(objspace, (VALUE)p);
        objspace->total_freed_object_num++;
        if (!FL_TEST(p, FL_SINGLETON)) { /* not freeing page */
            add_slot_local_freelist(objspace, p);
            objspace->heap.free_num++;
        }
        else {
            struct heaps_slot *slot = (struct heaps_slot *)(VALUE)RDATA(p)->dmark;
            slot->header->limit--;
        }
        p = tmp;
    }
}

static void
finalize_deferred(rb_objspace_t *objspace)
{
    RVALUE *p;

    while ((p = ATOMIC_PTR_EXCHANGE(deferred_final_list, 0)) != 0) {
        finalize_list(objspace, p);
    }
}

void
rb_gc_finalize_deferred(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    if (ATOMIC_EXCHANGE(finalizing, 1)) return;
    finalize_deferred(objspace);
    ATOMIC_SET(finalizing, 0);
}

struct force_finalize_list {
    VALUE obj;
    VALUE table;
    struct force_finalize_list *next;
};

static int
force_chain_object(st_data_t key, st_data_t val, st_data_t arg)
{
    struct force_finalize_list **prev = (struct force_finalize_list **)arg;
    struct force_finalize_list *curr = ALLOC(struct force_finalize_list);
    curr->obj = key;
    curr->table = val;
    curr->next = *prev;
    *prev = curr;
    return ST_CONTINUE;
}

void
rb_gc_call_finalizer_at_exit(void)
{
    rb_objspace_call_finalizer(&rb_objspace);
}

static void
rb_objspace_call_finalizer(rb_objspace_t *objspace)
{
    RVALUE *p, *pend;
    RVALUE *final_list = 0;
    size_t i;

    rest_sweep(objspace);

    if (ATOMIC_EXCHANGE(finalizing, 1)) return;

    /* run finalizers */
    finalize_deferred(objspace);
    assert(deferred_final_list == 0);

    /* force to run finalizer */
    while (finalizer_table->num_entries) {
        struct force_finalize_list *list = 0;
        st_foreach(finalizer_table, force_chain_object, (st_data_t)&list);
        while (list) {
            struct force_finalize_list *curr = list;
            st_data_t obj = (st_data_t)curr->obj;
            run_finalizer(objspace, curr->obj, curr->table);
            st_delete(finalizer_table, &obj, 0);
            list = curr->next;
            xfree(curr);
        }
    }

    /* finalizers are part of garbage collection */
    during_gc++;

    /* run data object's finalizers */
    for (i = 0; i < heaps_used; i++) {
        p = objspace->heap.sorted[i]->start; pend = p + objspace->heap.sorted[i]->limit;
        while (p < pend) {
            if (BUILTIN_TYPE(p) == T_DATA &&
                DATA_PTR(p) && RANY(p)->as.data.dfree &&
                !rb_obj_is_thread((VALUE)p) && !rb_obj_is_mutex((VALUE)p) &&
                !rb_obj_is_fiber((VALUE)p)) {
                p->as.free.flags = 0;
                if (RTYPEDDATA_P(p)) {
                    RDATA(p)->dfree = RANY(p)->as.typeddata.type->function.dfree;
                }
                if (RANY(p)->as.data.dfree == (RUBY_DATA_FUNC)-1) {
                    xfree(DATA_PTR(p));
                }
                else if (RANY(p)->as.data.dfree) {
                    make_deferred(RANY(p));
                    RANY(p)->as.free.next = final_list;
                    final_list = p;
                }
            }
            else if (BUILTIN_TYPE(p) == T_FILE) {
                if (RANY(p)->as.file.fptr) {
                    make_io_deferred(RANY(p));
                    RANY(p)->as.free.next = final_list;
                    final_list = p;
                }
            }
            p++;
        }
    }
    during_gc = 0;
    if (final_list) {
        finalize_list(objspace, final_list);
    }

    st_free_table(finalizer_table);
    finalizer_table = 0;
    ATOMIC_SET(finalizing, 0);
}

static inline int
is_id_value(rb_objspace_t *objspace, VALUE ptr)
{
    if (!is_pointer_to_heap(objspace, (void *)ptr)) return FALSE;
    if (BUILTIN_TYPE(ptr) > T_FIXNUM) return FALSE;
    if (BUILTIN_TYPE(ptr) == T_ICLASS) return FALSE;
    return TRUE;
}

static inline int
is_swept_object(rb_objspace_t *objspace, VALUE ptr)
{
    struct heaps_slot *slot = objspace->heap.sweep_slots;

    while (slot) {
        if ((VALUE)slot->header->start <= ptr && ptr < (VALUE)(slot->header->end))
            return FALSE;
        slot = slot->next;
    }
    return TRUE;
}

static inline int
is_dead_object(rb_objspace_t *objspace, VALUE ptr)
{
    if (!is_lazy_sweeping(objspace) || MARKED_IN_BITMAP(GET_HEAP_BITMAP(ptr), ptr))
        return FALSE;
    if (!is_swept_object(objspace, ptr))
        return TRUE;
    return FALSE;
}

static inline int
is_live_object(rb_objspace_t *objspace, VALUE ptr)
{
    if (BUILTIN_TYPE(ptr) == 0) return FALSE;
    if (RBASIC(ptr)->klass == 0) return FALSE;
    if (is_dead_object(objspace, ptr)) return FALSE;
    return TRUE;
}

/*
 *  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, VALUE objid)
{
#if SIZEOF_LONG == SIZEOF_VOIDP
#define NUM2PTR(x) NUM2ULONG(x)
#elif SIZEOF_LONG_LONG == SIZEOF_VOIDP
#define NUM2PTR(x) NUM2ULL(x)
#endif
    rb_objspace_t *objspace = &rb_objspace;
    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)) return (VALUE)ptr;
    if (FLONUM_P(ptr)) return (VALUE)ptr;
    ptr = obj_id_to_ref(objid);

    if ((ptr % sizeof(RVALUE)) == (4 << 2)) {
        ID symid = ptr / sizeof(RVALUE);
        if (rb_id2name(symid) == 0)
            rb_raise(rb_eRangeError, "%p is not symbol id value", p0);
        return ID2SYM(symid);
    }

    if (!is_id_value(objspace, ptr)) {
        rb_raise(rb_eRangeError, "%p is not id value", p0);
    }
    if (!is_live_object(objspace, ptr)) {
        rb_raise(rb_eRangeError, "%p is recycled object", p0);
    }
    return (VALUE)ptr;
}

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

/*
 *  call-seq:
 *     obj.hash    -> fixnum
 *
 *  Generates a Fixnum 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 Hash class.
 *
 *  Any hash value that exceeds the capacity of a Fixnum will be truncated
 *  before being used.
 */

VALUE
rb_obj_id(VALUE obj)
{
    /*
     *                32-bit VALUE space
     *          MSB ------------------------ LSB
     *  false   00000000000000000000000000000000
     *  true    00000000000000000000000000000010
     *  nil     00000000000000000000000000000100
     *  undef   00000000000000000000000000000110
     *  symbol  ssssssssssssssssssssssss00001110
     *  object  oooooooooooooooooooooooooooooo00        = 0 (mod sizeof(RVALUE))
     *  fixnum  fffffffffffffffffffffffffffffff1
     *
     *                    object_id space
     *                                       LSB
     *  false   00000000000000000000000000000000
     *  true    00000000000000000000000000000010
     *  nil     00000000000000000000000000000100
     *  undef   00000000000000000000000000000110
     *  symbol   000SSSSSSSSSSSSSSSSSSSSSSSSSSS0        S...S % A = 4 (S...S = s...s * A + 4)
     *  object   oooooooooooooooooooooooooooooo0        o...o % A = 0
     *  fixnum  fffffffffffffffffffffffffffffff1        bignum if required
     *
     *  where A = sizeof(RVALUE)/4
     *
     *  sizeof(RVALUE) is
     *  20 if 32-bit, double is 4-byte aligned
     *  24 if 32-bit, double is 8-byte aligned
     *  40 if 64-bit
     */
    if (SYMBOL_P(obj)) {
        return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG;
    }
    else if (FLONUM_P(obj)) {
#if SIZEOF_LONG == SIZEOF_VOIDP
        return LONG2NUM((SIGNED_VALUE)obj);
#else
        return LL2NUM((SIGNED_VALUE)obj);
#endif
    }
    else if (SPECIAL_CONST_P(obj)) {
        return LONG2NUM((SIGNED_VALUE)obj);
    }
    return nonspecial_obj_id(obj);
}

static int
set_zero(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;
}

/*
 *  call-seq:
 *     ObjectSpace.count_objects([result_hash]) -> hash
 *
 *  Counts objects for each type.
 *
 *  It returns a hash, such as:
 *      {
 *        :TOTAL=>10000,
 *        :FREE=>3011,
 *        :T_OBJECT=>6,
 *        :T_CLASS=>404,
 *        # ...
 *      }
 *
 *  The contents of the returned hash are implementation specific.
 *  It may be changed in future.
 *
 *  If the optional argument +result_hash+ is given,
 *  it is overwritten and returned. This is intended to avoid probe effect.
 *
 *  This method is only expected to work on C Ruby.
 *
 */

static VALUE
count_objects(int argc, VALUE *argv, VALUE os)
{
    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 (!RB_TYPE_P(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 = objspace->heap.sorted[i]->start; pend = p + objspace->heap.sorted[i]->limit;
        for (;p < pend; p++) {
            if (p->as.basic.flags) {
                counts[BUILTIN_TYPE(p)]++;
            }
            else {
                freed++;
            }
        }
        total += objspace->heap.sorted[i]->limit;
    }

    if (hash == Qnil) {
        hash = rb_hash_new();
    }
    else if (!RHASH_EMPTY_P(hash)) {
        st_foreach(RHASH_TBL(hash), set_zero, hash);
    }
    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_UNDEF);
            COUNT_TYPE(T_NODE);
            COUNT_TYPE(T_ICLASS);
            COUNT_TYPE(T_ZOMBIE);
#undef COUNT_TYPE
          default:              type = INT2NUM(i); break;
        }
        if (counts[i])
            rb_hash_aset(hash, type, SIZET2NUM(counts[i]));
    }

    return hash;
}



/*
  ------------------------ Garbage Collection ------------------------
*/

/* Sweeping */

static VALUE
lazy_sweep_enable(void)
{
    rb_objspace_t *objspace = &rb_objspace;

    objspace->flags.dont_lazy_sweep = FALSE;
    return Qnil;
}

static void
gc_clear_slot_bits(struct heaps_slot *slot)
{
    memset(slot->bits, 0, HEAP_BITMAP_LIMIT * sizeof(uintptr_t));
}

static size_t
objspace_live_num(rb_objspace_t *objspace)
{
    return objspace->total_allocated_object_num - objspace->total_freed_object_num;
}

static void
slot_sweep(rb_objspace_t *objspace, struct heaps_slot *sweep_slot)
{
    size_t empty_num = 0, freed_num = 0, final_num = 0;
    RVALUE *p, *pend;
    RVALUE *final = deferred_final_list;
    int deferred;
    uintptr_t *bits;

    p = sweep_slot->header->start; pend = p + sweep_slot->header->limit;
    bits = GET_HEAP_BITMAP(p);
    while (p < pend) {
        if ((!(MARKED_IN_BITMAP(bits, p))) && BUILTIN_TYPE(p) != T_ZOMBIE) {
            if (p->as.basic.flags) {
                if ((deferred = obj_free(objspace, (VALUE)p)) ||
                    (FL_TEST(p, FL_FINALIZE))) {
                    if (!deferred) {
                        p->as.free.flags = T_ZOMBIE;
                        RDATA(p)->dfree = 0;
                    }
                    p->as.free.next = deferred_final_list;
                    deferred_final_list = p;
                    assert(BUILTIN_TYPE(p) == T_ZOMBIE);
                    final_num++;
                }
                else {
                    (void)VALGRIND_MAKE_MEM_UNDEFINED((void*)p, sizeof(RVALUE));
                    p->as.free.flags = 0;
                    p->as.free.next = sweep_slot->freelist;
                    sweep_slot->freelist = p;
                    freed_num++;
                }
            }
            else {
                empty_num++;
            }
        }
        p++;
    }
    gc_clear_slot_bits(sweep_slot);
    if (final_num + freed_num + empty_num == sweep_slot->header->limit &&
        objspace->heap.free_num > objspace->heap.do_heap_free) {
        RVALUE *pp;

        for (pp = deferred_final_list; pp != final; pp = pp->as.free.next) {
            RDATA(pp)->dmark = (void (*)(void *))(VALUE)sweep_slot;
            pp->as.free.flags |= FL_SINGLETON; /* freeing page mark */
        }
        sweep_slot->header->limit = final_num;
        unlink_heap_slot(objspace, sweep_slot);
    }
    else {
        if (freed_num + empty_num > 0) {
            link_free_heap_slot(objspace, sweep_slot);
        }
        else {
            sweep_slot->free_next = NULL;
        }
        objspace->heap.free_num += freed_num + empty_num;
    }
    objspace->total_freed_object_num += freed_num;
    objspace->heap.final_num += final_num;

    if (deferred_final_list && !finalizing) {
        rb_thread_t *th = GET_THREAD();
        if (th) {
            RUBY_VM_SET_FINALIZER_INTERRUPT(th);
        }
    }
}

static int
ready_to_gc(rb_objspace_t *objspace)
{
    if (dont_gc || during_gc) {
        if (!has_free_object) {
            if (!heaps_increment(objspace)) {
                set_heaps_increment(objspace);
                heaps_increment(objspace);
            }
        }
        return FALSE;
    }
    return TRUE;
}

static void
before_gc_sweep(rb_objspace_t *objspace)
{
    objspace->heap.do_heap_free = (size_t)((heaps_used * HEAP_OBJ_LIMIT) * 0.65);
    objspace->heap.free_min = (size_t)((heaps_used * HEAP_OBJ_LIMIT)  * 0.2);
    if (objspace->heap.free_min < initial_free_min) {
        objspace->heap.free_min = initial_free_min;
        if (objspace->heap.do_heap_free < initial_free_min)
            objspace->heap.do_heap_free = initial_free_min;
    }
    objspace->heap.sweep_slots = heaps;
    objspace->heap.free_num = 0;
    objspace->heap.free_slots = NULL;

    /* sweep unlinked method entries */
    if (GET_VM()->unlinked_method_entry_list) {
        rb_sweep_method_entry(GET_VM());
    }
}

static void
after_gc_sweep(rb_objspace_t *objspace)
{
    size_t inc;

    gc_prof_set_malloc_info(objspace);
    if (objspace->heap.free_num < objspace->heap.free_min) {
        set_heaps_increment(objspace);
        heaps_increment(objspace);
    }

    inc = ATOMIC_SIZE_EXCHANGE(malloc_increase, 0);
    if (inc > malloc_limit) {
        malloc_limit +=
          (size_t)((inc - malloc_limit) * (double)objspace->heap.marked_num / (heaps_used * HEAP_OBJ_LIMIT));
        if (malloc_limit < initial_malloc_limit) malloc_limit = initial_malloc_limit;
    }

    free_unused_heaps(objspace);
}

static int
lazy_sweep(rb_objspace_t *objspace)
{
    struct heaps_slot *next;

    heaps_increment(objspace);
    while (objspace->heap.sweep_slots) {
        next = objspace->heap.sweep_slots->next;
        slot_sweep(objspace, objspace->heap.sweep_slots);
        objspace->heap.sweep_slots = next;
        if (has_free_object) {
            during_gc = 0;
            return TRUE;
        }
    }
    return FALSE;
}

static void
rest_sweep(rb_objspace_t *objspace)
{
    if (objspace->heap.sweep_slots) {
        while (objspace->heap.sweep_slots) {
            lazy_sweep(objspace);
        }
        after_gc_sweep(objspace);
    }
}

static void gc_marks(rb_objspace_t *objspace);

static int
gc_prepare_free_objects(rb_objspace_t *objspace)
{
    int res;

    if (objspace->flags.dont_lazy_sweep)
        return garbage_collect(objspace);


    if (!ready_to_gc(objspace)) return TRUE;

    during_gc++;
    gc_prof_timer_start(objspace);
    gc_prof_sweep_timer_start(objspace);

    if (objspace->heap.sweep_slots) {
        res = lazy_sweep(objspace);
        if (res) {
            gc_prof_sweep_timer_stop(objspace);
            gc_prof_set_malloc_info(objspace);
            gc_prof_timer_stop(objspace, Qfalse);
            return res;
        }
        after_gc_sweep(objspace);
    }
    else {
        if (heaps_increment(objspace)) {
            during_gc = 0;
            return TRUE;
        }
    }

    gc_marks(objspace);

    before_gc_sweep(objspace);
    if (objspace->heap.free_min > (heaps_used * HEAP_OBJ_LIMIT - objspace->heap.marked_num)) {
        set_heaps_increment(objspace);
    }

    gc_prof_sweep_timer_start(objspace);
    if (!(res = lazy_sweep(objspace))) {
        after_gc_sweep(objspace);
        if (has_free_object) {
            res = TRUE;
            during_gc = 0;
        }
    }
    gc_prof_sweep_timer_stop(objspace);

    gc_prof_timer_stop(objspace, Qtrue);
    return res;
}

static void
gc_sweep(rb_objspace_t *objspace)
{
    struct heaps_slot *next;

    before_gc_sweep(objspace);

    while (objspace->heap.sweep_slots) {
        next = objspace->heap.sweep_slots->next;
        slot_sweep(objspace, objspace->heap.sweep_slots);
        objspace->heap.sweep_slots = next;
    }

    after_gc_sweep(objspace);

    during_gc = 0;
}

/* Marking stack */

static void push_mark_stack(mark_stack_t *, VALUE);
static int pop_mark_stack(mark_stack_t *, VALUE *);
static void shrink_stack_chunk_cache(mark_stack_t *stack);

static stack_chunk_t *
stack_chunk_alloc(void)
{
    stack_chunk_t *res;

    res = malloc(sizeof(stack_chunk_t));
    if (!res)
        rb_memerror();

    return res;
}

static inline int
is_mark_stask_empty(mark_stack_t *stack)
{
    return stack->chunk == NULL;
}

static void
add_stack_chunk_cache(mark_stack_t *stack, stack_chunk_t *chunk)
{
    chunk->next = stack->cache;
    stack->cache = chunk;
    stack->cache_size++;
}

static void
shrink_stack_chunk_cache(mark_stack_t *stack)
{
    stack_chunk_t *chunk;

    if (stack->unused_cache_size > (stack->cache_size/2)) {
        chunk = stack->cache;
        stack->cache = stack->cache->next;
        stack->cache_size--;
        free(chunk);
    }
    stack->unused_cache_size = stack->cache_size;
}

static void
push_mark_stack_chunk(mark_stack_t *stack)
{
    stack_chunk_t *next;

    assert(stack->index == stack->limit);
    if (stack->cache_size > 0) {
        next = stack->cache;
        stack->cache = stack->cache->next;
        stack->cache_size--;
        if (stack->unused_cache_size > stack->cache_size)
            stack->unused_cache_size = stack->cache_size;
    }
    else {
        next = stack_chunk_alloc();
    }
    next->next = stack->chunk;
    stack->chunk = next;
    stack->index = 0;
}

static void
pop_mark_stack_chunk(mark_stack_t *stack)
{
    stack_chunk_t *prev;

    prev = stack->chunk->next;
    assert(stack->index == 0);
    add_stack_chunk_cache(stack, stack->chunk);
    stack->chunk = prev;
    stack->index = stack->limit;
}

#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
static void
free_stack_chunks(mark_stack_t *stack)
{
    stack_chunk_t *chunk = stack->chunk;
    stack_chunk_t *next = NULL;

    while (chunk != NULL) {
        next = chunk->next;
        free(chunk);
        chunk = next;
    }
}
#endif

static void
push_mark_stack(mark_stack_t *stack, VALUE data)
{
    if (stack->index == stack->limit) {
        push_mark_stack_chunk(stack);
    }
    stack->chunk->data[stack->index++] = data;
}

static int
pop_mark_stack(mark_stack_t *stack, VALUE *data)
{
    if (is_mark_stask_empty(stack)) {
        return FALSE;
    }
    if (stack->index == 1) {
        *data = stack->chunk->data[--stack->index];
        pop_mark_stack_chunk(stack);
        return TRUE;
    }
    *data = stack->chunk->data[--stack->index];
    return TRUE;
}

static void
init_mark_stack(mark_stack_t *stack)
{
    int i;

    push_mark_stack_chunk(stack);
    stack->limit = STACK_CHUNK_SIZE;

    for (i=0; i < 4; i++) {
        add_stack_chunk_cache(stack, stack_chunk_alloc());
    }
    stack->unused_cache_size = stack->cache_size;
}


/* Marking */

#define MARK_IN_BITMAP(bits, p) (bits[BITMAP_INDEX(p)] = bits[BITMAP_INDEX(p)] | ((uintptr_t)1 << BITMAP_OFFSET(p)))


#ifdef __ia64
#define SET_STACK_END (SET_MACHINE_STACK_END(&th->machine_stack_end), th->machine_register_stack_end = rb_ia64_bsp())
#else
#define SET_STACK_END SET_MACHINE_STACK_END(&th->machine_stack_end)
#endif

#define STACK_START (th->machine_stack_start)
#define STACK_END (th->machine_stack_end)
#define STACK_LEVEL_MAX (th->machine_stack_maxsize/sizeof(VALUE))

#if STACK_GROW_DIRECTION < 0
# define STACK_LENGTH  (size_t)(STACK_START - STACK_END)
#elif STACK_GROW_DIRECTION > 0
# define STACK_LENGTH  (size_t)(STACK_END - STACK_START + 1)
#else
# define STACK_LENGTH  ((STACK_END < STACK_START) ? (size_t)(STACK_START - STACK_END) \
                        : (size_t)(STACK_END - STACK_START + 1))
#endif
#if !STACK_GROW_DIRECTION
int ruby_stack_grow_direction;
int
ruby_get_stack_grow_direction(volatile VALUE *addr)
{
    VALUE *end;
    SET_MACHINE_STACK_END(&end);

    if (end > addr) return ruby_stack_grow_direction = 1;
    return ruby_stack_grow_direction = -1;
}
#endif

size_t
ruby_stack_length(VALUE **p)
{
    rb_thread_t *th = GET_THREAD();
    SET_STACK_END;
    if (p) *p = STACK_UPPER(STACK_END, STACK_START, STACK_END);
    return STACK_LENGTH;
}

#if !(defined(POSIX_SIGNAL) && defined(SIGSEGV) && defined(HAVE_SIGALTSTACK))
static int
stack_check(int water_mark)
{
    int ret;
    rb_thread_t *th = GET_THREAD();
    SET_STACK_END;
    ret = STACK_LENGTH > STACK_LEVEL_MAX - water_mark;
#ifdef __ia64
    if (!ret) {
        ret = (VALUE*)rb_ia64_bsp() - th->machine_register_stack_start >
              th->machine_register_stack_maxsize/sizeof(VALUE) - water_mark;
    }
#endif
    return ret;
}
#endif

#define STACKFRAME_FOR_CALL_CFUNC 512

int
ruby_stack_check(void)
{
#if defined(POSIX_SIGNAL) && defined(SIGSEGV) && defined(HAVE_SIGALTSTACK)
    return 0;
#else
    return stack_check(STACKFRAME_FOR_CALL_CFUNC);
#endif
}

static void
mark_locations_array(rb_objspace_t *objspace, register VALUE *x, register long n)
{
    VALUE v;
    while (n--) {
        v = *x;
        (void)VALGRIND_MAKE_MEM_DEFINED(&v, sizeof(v));
        if (is_pointer_to_heap(objspace, (void *)v)) {
            gc_mark(objspace, v);
        }
        x++;
    }
}

static void
gc_mark_locations(rb_objspace_t *objspace, VALUE *start, VALUE *end)
{
    long n;

    if (end <= start) return;
    n = end - start;
    mark_locations_array(objspace, start, n);
}

void
rb_gc_mark_locations(VALUE *start, VALUE *end)
{
    gc_mark_locations(&rb_objspace, start, end);
}

#define rb_gc_mark_locations(start, end) gc_mark_locations(objspace, (start), (end))

struct mark_tbl_arg {
    rb_objspace_t *objspace;
};

static int
mark_entry(st_data_t key, st_data_t value, st_data_t data)
{
    struct mark_tbl_arg *arg = (void*)data;
    gc_mark(arg->objspace, (VALUE)value);
    return ST_CONTINUE;
}

static void
mark_tbl(rb_objspace_t *objspace, st_table *tbl)
{
    struct mark_tbl_arg arg;
    if (!tbl || tbl->num_entries == 0) return;
    arg.objspace = objspace;
    st_foreach(tbl, mark_entry, (st_data_t)&arg);
}

static int
mark_key(st_data_t key, st_data_t value, st_data_t data)
{
    struct mark_tbl_arg *arg = (void*)data;
    gc_mark(arg->objspace, (VALUE)key);
    return ST_CONTINUE;
}

static void
mark_set(rb_objspace_t *objspace, st_table *tbl)
{
    struct mark_tbl_arg arg;
    if (!tbl) return;
    arg.objspace = objspace;
    st_foreach(tbl, mark_key, (st_data_t)&arg);
}

void
rb_mark_set(st_table *tbl)
{
    mark_set(&rb_objspace, tbl);
}

static int
mark_keyvalue(st_data_t key, st_data_t value, st_data_t data)
{
    struct mark_tbl_arg *arg = (void*)data;
    gc_mark(arg->objspace, (VALUE)key);
    gc_mark(arg->objspace, (VALUE)value);
    return ST_CONTINUE;
}

static void
mark_hash(rb_objspace_t *objspace, st_table *tbl)
{
    struct mark_tbl_arg arg;
    if (!tbl) return;
    arg.objspace = objspace;
    st_foreach(tbl, mark_keyvalue, (st_data_t)&arg);
}

void
rb_mark_hash(st_table *tbl)
{
    mark_hash(&rb_objspace, tbl);
}

static void
mark_method_entry(rb_objspace_t *objspace, const rb_method_entry_t *me)
{
    const rb_method_definition_t *def = me->def;

    gc_mark(objspace, me->klass);
  again:
    if (!def) return;
    switch (def->type) {
      case VM_METHOD_TYPE_ISEQ:
        gc_mark(objspace, def->body.iseq->self);
        break;
      case VM_METHOD_TYPE_BMETHOD:
        gc_mark(objspace, def->body.proc);
        break;
      case VM_METHOD_TYPE_ATTRSET:
      case VM_METHOD_TYPE_IVAR:
        gc_mark(objspace, def->body.attr.location);
        break;
      case VM_METHOD_TYPE_REFINED:
        if (def->body.orig_me) {
            def = def->body.orig_me->def;
            goto again;
        }
        break;
      default:
        break; /* ignore */
    }
}

void
rb_mark_method_entry(const rb_method_entry_t *me)
{
    mark_method_entry(&rb_objspace, me);
}

static int
mark_method_entry_i(ID key, const rb_method_entry_t *me, st_data_t data)
{
    struct mark_tbl_arg *arg = (void*)data;
    mark_method_entry(arg->objspace, me);
    return ST_CONTINUE;
}

static void
mark_m_tbl(rb_objspace_t *objspace, st_table *tbl)
{
    struct mark_tbl_arg arg;
    if (!tbl) return;
    arg.objspace = objspace;
    st_foreach(tbl, mark_method_entry_i, (st_data_t)&arg);
}

static int
mark_const_entry_i(ID key, const rb_const_entry_t *ce, st_data_t data)
{
    struct mark_tbl_arg *arg = (void*)data;
    gc_mark(arg->objspace, ce->value);
    gc_mark(arg->objspace, ce->file);
    return ST_CONTINUE;
}

static void
mark_const_tbl(rb_objspace_t *objspace, st_table *tbl)
{
    struct mark_tbl_arg arg;
    if (!tbl) return;
    arg.objspace = objspace;
    st_foreach(tbl, mark_const_entry_i, (st_data_t)&arg);
}

#if STACK_GROW_DIRECTION < 0
#define GET_STACK_BOUNDS(start, end, appendix) ((start) = STACK_END, (end) = STACK_START)
#elif STACK_GROW_DIRECTION > 0
#define GET_STACK_BOUNDS(start, end, appendix) ((start) = STACK_START, (end) = STACK_END+(appendix))
#else
#define GET_STACK_BOUNDS(start, end, appendix) \
    ((STACK_END < STACK_START) ? \
     ((start) = STACK_END, (end) = STACK_START) : ((start) = STACK_START, (end) = STACK_END+(appendix)))
#endif

#define numberof(array) (int)(sizeof(array) / sizeof((array)[0]))

static void
mark_current_machine_context(rb_objspace_t *objspace, rb_thread_t *th)
{
    union {
        rb_jmp_buf j;
        VALUE v[sizeof(rb_jmp_buf) / sizeof(VALUE)];
    } save_regs_gc_mark;
    VALUE *stack_start, *stack_end;

    FLUSH_REGISTER_WINDOWS;
    /* This assumes that all registers are saved into the jmp_buf (and stack) */
    rb_setjmp(save_regs_gc_mark.j);

    SET_STACK_END;
    GET_STACK_BOUNDS(stack_start, stack_end, 1);

    mark_locations_array(objspace, save_regs_gc_mark.v, numberof(save_regs_gc_mark.v));

    rb_gc_mark_locations(stack_start, stack_end);
#ifdef __ia64
    rb_gc_mark_locations(th->machine_register_stack_start, th->machine_register_stack_end);
#endif
#if defined(__mc68000__)
    mark_locations_array(objspace, (VALUE*)((char*)STACK_END + 2),
                         (STACK_START - STACK_END));
#endif
}

void
rb_gc_mark_machine_stack(rb_thread_t *th)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE *stack_start, *stack_end;

    GET_STACK_BOUNDS(stack_start, stack_end, 0);
    rb_gc_mark_locations(stack_start, stack_end);
#ifdef __ia64
    rb_gc_mark_locations(th->machine_register_stack_start, th->machine_register_stack_end);
#endif
}

void
rb_mark_tbl(st_table *tbl)
{
    mark_tbl(&rb_objspace, tbl);
}

void
rb_gc_mark_maybe(VALUE obj)
{
    if (is_pointer_to_heap(&rb_objspace, (void *)obj)) {
        gc_mark(&rb_objspace, obj);
    }
}

static int
gc_mark_ptr(rb_objspace_t *objspace, VALUE ptr)
{
    register uintptr_t *bits = GET_HEAP_BITMAP(ptr);
    if (MARKED_IN_BITMAP(bits, ptr)) return 0;
    MARK_IN_BITMAP(bits, ptr);
    objspace->heap.marked_num++;
    return 1;
}

static int
markable_object_p(rb_objspace_t *objspace, VALUE ptr)
{
    register RVALUE *obj = RANY(ptr);

    if (rb_special_const_p(ptr)) return 0; /* special const not marked */
    if (obj->as.basic.flags == 0) return 0 ;       /* free cell */

    return 1;
}

int
rb_objspace_markable_object_p(VALUE obj)
{
    return markable_object_p(/* now it doesn't use &rb_objspace */ 0, obj);
}

static void
gc_mark(rb_objspace_t *objspace, VALUE ptr)
{
    if (!markable_object_p(objspace, ptr)) {
        return;
    }

    if (LIKELY(objspace->mark_func_data == 0)) {
        if (!gc_mark_ptr(objspace, ptr)) return; /* already marked */
        push_mark_stack(&objspace->mark_stack, ptr);
    }
    else {
        objspace->mark_func_data->mark_func(ptr, objspace->mark_func_data->data);
    }
}

void
rb_gc_mark(VALUE ptr)
{
    gc_mark(&rb_objspace, ptr);
}

static void
gc_mark_children(rb_objspace_t *objspace, VALUE ptr)
{
    register RVALUE *obj = RANY(ptr);

    goto marking;               /* skip */

  again:
    if (LIKELY(objspace->mark_func_data == 0)) {
        obj = RANY(ptr);
        if (!markable_object_p(objspace, ptr)) return;
        if (!gc_mark_ptr(objspace, ptr)) return;  /* already marked */
    }
    else {
        gc_mark(objspace, ptr);
        return;
    }

  marking:
    if (FL_TEST(obj, FL_EXIVAR)) {
        rb_mark_generic_ivar(ptr);
    }

    switch (BUILTIN_TYPE(obj)) {
      case T_NIL:
      case T_FIXNUM:
        rb_bug("rb_gc_mark() called for broken object");
        break;

      case T_NODE:
        switch (nd_type(obj)) {
          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:
            gc_mark(objspace, (VALUE)obj->as.node.u2.node);
            /* fall through */
          case NODE_BLOCK:      /* 1,3 */
          case NODE_ARRAY:
          case NODE_DSTR:
          case NODE_DXSTR:
          case NODE_DREGX:
          case NODE_DREGX_ONCE:
          case NODE_ENSURE:
          case NODE_CALL:
          case NODE_DEFS:
          case NODE_OP_ASGN1:
            gc_mark(objspace, (VALUE)obj->as.node.u1.node);
            /* fall through */
          case NODE_SUPER:      /* 3 */
          case NODE_FCALL:
          case NODE_DEFN:
          case NODE_ARGS_AUX:
            ptr = (VALUE)obj->as.node.u3.node;
            goto again;

          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_ALIAS:
          case NODE_VALIAS:
          case NODE_ARGSCAT:
            gc_mark(objspace, (VALUE)obj->as.node.u1.node);
            /* fall through */
          case NODE_GASGN:      /* 2 */
          case NODE_LASGN:
          case NODE_DASGN:
          case NODE_DASGN_CURR:
          case NODE_IASGN:
          case NODE_IASGN2:
          case NODE_CVASGN:
          case NODE_COLON3:
          case NODE_OPT_N:
          case NODE_EVSTR:
          case NODE_UNDEF:
          case NODE_POSTEXE:
            ptr = (VALUE)obj->as.node.u2.node;
            goto again;

          case NODE_HASH:       /* 1 */
          case NODE_LIT:
          case NODE_STR:
          case NODE_XSTR:
          case NODE_DEFINED:
          case NODE_MATCH:
          case NODE_RETURN:
          case NODE_BREAK:
          case NODE_NEXT:
          case NODE_YIELD:
          case NODE_COLON2:
          case NODE_SPLAT:
          case NODE_TO_ARY:
            ptr = (VALUE)obj->as.node.u1.node;
            goto again;

          case NODE_SCOPE:      /* 2,3 */
          case NODE_CDECL:
          case NODE_OPT_ARG:
            gc_mark(objspace, (VALUE)obj->as.node.u3.node);
            ptr = (VALUE)obj->as.node.u2.node;
            goto again;

          case NODE_ARGS:       /* custom */
            {
                struct rb_args_info *args = obj->as.node.u3.args;
                if (args) {
                    if (args->pre_init)    gc_mark(objspace, (VALUE)args->pre_init);
                    if (args->post_init)   gc_mark(objspace, (VALUE)args->post_init);
                    if (args->opt_args)    gc_mark(objspace, (VALUE)args->opt_args);
                    if (args->kw_args)     gc_mark(objspace, (VALUE)args->kw_args);
                    if (args->kw_rest_arg) gc_mark(objspace, (VALUE)args->kw_rest_arg);
                }
            }
            ptr = (VALUE)obj->as.node.u2.node;
            goto again;

          case NODE_ZARRAY:     /* - */
          case NODE_ZSUPER:
          case NODE_VCALL:
          case NODE_GVAR:
          case NODE_LVAR:
          case NODE_DVAR:
          case NODE_IVAR:
          case NODE_CVAR:
          case NODE_NTH_REF:
          case NODE_BACK_REF:
          case NODE_REDO:
          case NODE_RETRY:
          case NODE_SELF:
          case NODE_NIL:
          case NODE_TRUE:
          case NODE_FALSE:
          case NODE_ERRINFO:
          case NODE_BLOCK_ARG:
            break;
          case NODE_ALLOCA:
            mark_locations_array(objspace,
                                 (VALUE*)obj->as.node.u1.value,
                                 obj->as.node.u3.cnt);
            gc_mark(objspace, (VALUE)obj->as.node.u2.node);
            break;

          case NODE_CREF:
            gc_mark(objspace, obj->as.node.nd_refinements);
            gc_mark(objspace, (VALUE)obj->as.node.u1.node);
            ptr = (VALUE)obj->as.node.u3.node;
            goto again;

          default:              /* unlisted NODE */
            if (is_pointer_to_heap(objspace, obj->as.node.u1.node)) {
                gc_mark(objspace, (VALUE)obj->as.node.u1.node);
            }
            if (is_pointer_to_heap(objspace, obj->as.node.u2.node)) {
                gc_mark(objspace, (VALUE)obj->as.node.u2.node);
            }
            if (is_pointer_to_heap(objspace, obj->as.node.u3.node)) {
                gc_mark(objspace, (VALUE)obj->as.node.u3.node);
            }
        }
        return;                 /* no need to mark class. */
    }

    gc_mark(objspace, obj->as.basic.klass);
    switch (BUILTIN_TYPE(obj)) {
      case T_ICLASS:
      case T_CLASS:
      case T_MODULE:
        mark_m_tbl(objspace, RCLASS_M_TBL(obj));
        if (!RCLASS_EXT(obj)) break;
        mark_tbl(objspace, RCLASS_IV_TBL(obj));
        mark_const_tbl(objspace, RCLASS_CONST_TBL(obj));
        ptr = RCLASS_SUPER(obj);
        goto again;

      case T_ARRAY:
        if (FL_TEST(obj, ELTS_SHARED)) {
            ptr = obj->as.array.as.heap.aux.shared;
            goto again;
        }
        else {
            long i, len = RARRAY_LEN(obj);
            VALUE *ptr = RARRAY_PTR(obj);
            for (i=0; i < len; i++) {
                gc_mark(objspace, *ptr++);
            }
        }
        break;

      case T_HASH:
        mark_hash(objspace, obj->as.hash.ntbl);
        ptr = obj->as.hash.ifnone;
        goto again;

      case T_STRING:
#define STR_ASSOC FL_USER3   /* copied from string.c */
        if (FL_TEST(obj, RSTRING_NOEMBED) && FL_ANY(obj, ELTS_SHARED|STR_ASSOC)) {
            ptr = obj->as.string.as.heap.aux.shared;
            goto again;
        }
        break;

      case T_DATA:
        if (RTYPEDDATA_P(obj)) {
            RUBY_DATA_FUNC mark_func = obj->as.typeddata.type->function.dmark;
            if (mark_func) (*mark_func)(DATA_PTR(obj));
        }
        else {
            if (obj->as.data.dmark) (*obj->as.data.dmark)(DATA_PTR(obj));
        }
        break;

      case T_OBJECT:
        {
            long i, len = ROBJECT_NUMIV(obj);
            VALUE *ptr = ROBJECT_IVPTR(obj);
            for (i  = 0; i < len; i++) {
                gc_mark(objspace, *ptr++);
            }
        }
        break;

      case T_FILE:
        if (obj->as.file.fptr) {
            gc_mark(objspace, obj->as.file.fptr->pathv);
            gc_mark(objspace, obj->as.file.fptr->tied_io_for_writing);
            gc_mark(objspace, obj->as.file.fptr->writeconv_asciicompat);
            gc_mark(objspace, obj->as.file.fptr->writeconv_pre_ecopts);
            gc_mark(objspace, obj->as.file.fptr->encs.ecopts);
            gc_mark(objspace, obj->as.file.fptr->write_lock);
        }
        break;

      case T_REGEXP:
        ptr = obj->as.regexp.src;
        goto again;

      case T_FLOAT:
      case T_BIGNUM:
      case T_ZOMBIE:
        break;

      case T_MATCH:
        gc_mark(objspace, obj->as.match.regexp);
        if (obj->as.match.str) {
            ptr = obj->as.match.str;
            goto again;
        }
        break;

      case T_RATIONAL:
        gc_mark(objspace, obj->as.rational.num);
        ptr = obj->as.rational.den;
        goto again;

      case T_COMPLEX:
        gc_mark(objspace, obj->as.complex.real);
        ptr = obj->as.complex.imag;
        goto again;

      case T_STRUCT:
        {
            long len = RSTRUCT_LEN(obj);
            VALUE *ptr = RSTRUCT_PTR(obj);

            while (len--) {
                gc_mark(objspace, *ptr++);
            }
        }
        break;

      default:
        rb_bug("rb_gc_mark(): unknown data type 0x%x(%p) %s",
               BUILTIN_TYPE(obj), (void *)obj,
               is_pointer_to_heap(objspace, obj) ? "corrupted object" : "non object");
    }
}

static void
gc_mark_stacked_objects(rb_objspace_t *objspace)
{
    mark_stack_t *mstack = &objspace->mark_stack;
    VALUE obj = 0;

    if (!mstack->index) return;
    while (pop_mark_stack(mstack, &obj)) {
        gc_mark_children(objspace, obj);
    }
    shrink_stack_chunk_cache(mstack);
}

static void
gc_marks(rb_objspace_t *objspace)
{
    struct gc_list *list;
    rb_thread_t *th = GET_THREAD();
    struct mark_func_data_struct *prev_mark_func_data;

    prev_mark_func_data = objspace->mark_func_data;
    objspace->mark_func_data = 0;

    gc_prof_mark_timer_start(objspace);
    objspace->heap.marked_num = 0;
    objspace->count++;

    SET_STACK_END;

    th->vm->self ? rb_gc_mark(th->vm->self) : rb_vm_mark(th->vm);

    mark_tbl(objspace, finalizer_table);
    mark_current_machine_context(objspace, th);

    rb_gc_mark_symbols();
    rb_gc_mark_encodings();

    /* mark protected global variables */
    for (list = global_List; list; list = list->next) {
        rb_gc_mark_maybe(*list->varptr);
    }
    rb_mark_end_proc();
    rb_gc_mark_global_tbl();

    mark_tbl(objspace, rb_class_tbl);

    /* mark generic instance variables for special constants */
    rb_mark_generic_ivar_tbl();

    rb_gc_mark_parser();

    rb_gc_mark_unlinked_live_method_entries(th->vm);

    /* marking-loop */
    gc_mark_stacked_objects(objspace);

    gc_prof_mark_timer_stop(objspace);

    objspace->mark_func_data = prev_mark_func_data;
}

/* GC */

void
rb_gc_force_recycle(VALUE p)
{
    rb_objspace_t *objspace = &rb_objspace;
    struct heaps_slot *slot;

    objspace->total_freed_object_num++;
    if (MARKED_IN_BITMAP(GET_HEAP_BITMAP(p), p)) {
        add_slot_local_freelist(objspace, (RVALUE *)p);
    }
    else {
        objspace->heap.free_num++;
        slot = add_slot_local_freelist(objspace, (RVALUE *)p);
        if (slot->free_next == NULL) {
            link_free_heap_slot(objspace, slot);
        }
    }
}

void
rb_gc_register_mark_object(VALUE obj)
{
    VALUE ary = GET_THREAD()->vm->mark_object_ary;
    rb_ary_push(ary, obj);
}

void
rb_gc_register_address(VALUE *addr)
{
    rb_objspace_t *objspace = &rb_objspace;
    struct gc_list *tmp;

    tmp = ALLOC(struct gc_list);
    tmp->next = global_List;
    tmp->varptr = addr;
    global_List = tmp;
}

void
rb_gc_unregister_address(VALUE *addr)
{
    rb_objspace_t *objspace = &rb_objspace;
    struct gc_list *tmp = global_List;

    if (tmp->varptr == addr) {
        global_List = tmp->next;
        xfree(tmp);
        return;
    }
    while (tmp->next) {
        if (tmp->next->varptr == addr) {
            struct gc_list *t = tmp->next;

            tmp->next = tmp->next->next;
            xfree(t);
            break;
        }
        tmp = tmp->next;
    }
}

#define GC_NOTIFY 0

static int
garbage_collect(rb_objspace_t *objspace)
{
    if (GC_NOTIFY) printf("start garbage_collect()\n");

    if (!heaps) {
        return FALSE;
    }
    if (!ready_to_gc(objspace)) {
        return TRUE;
    }

    gc_prof_timer_start(objspace);

    rest_sweep(objspace);

    during_gc++;
    gc_marks(objspace);

    gc_prof_sweep_timer_start(objspace);
    gc_sweep(objspace);
    gc_prof_sweep_timer_stop(objspace);

    gc_prof_timer_stop(objspace, Qtrue);
    if (GC_NOTIFY) printf("end garbage_collect()\n");
    return TRUE;
}

static void *
gc_with_gvl(void *ptr)
{
    return (void *)(VALUE)garbage_collect((rb_objspace_t *)ptr);
}

static int
garbage_collect_with_gvl(rb_objspace_t *objspace)
{
    if (dont_gc) return TRUE;
    if (ruby_thread_has_gvl_p()) {
        return garbage_collect(objspace);
    }
    else {
        if (ruby_native_thread_p()) {
            return (int)(VALUE)rb_thread_call_with_gvl(gc_with_gvl, (void *)objspace);
        }
        else {
            /* no ruby thread */
            fprintf(stderr, "[FATAL] failed to allocate memory\n");
            exit(EXIT_FAILURE);
        }
    }
}

int
rb_garbage_collect(void)
{
    return garbage_collect(&rb_objspace);
}

#undef Init_stack

void
Init_stack(volatile VALUE *addr)
{
    ruby_init_stack(addr);
}

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

VALUE
rb_gc_start(void)
{
    rb_gc();
    return Qnil;
}

void
rb_gc(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    garbage_collect(objspace);
    if (!finalizing) finalize_deferred(objspace);
    free_unused_heaps(objspace);
}

int
rb_during_gc(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    return during_gc;
}

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

static VALUE
gc_count(VALUE self)
{
    return UINT2NUM(rb_objspace.count);
}

/*
 *  call-seq:
 *     GC.stat -> Hash
 *
 *  Returns a Hash containing information about the GC.
 *
 *  The hash includes information about internal statistics about GC such as:
 *
 *      {
 *          :count=>0,
 *          :heap_used=>12,
 *          :heap_length=>12,
 *          :heap_increment=>0,
 *          :heap_live_num=>7539,
 *          :heap_free_num=>88,
 *          :heap_final_num=>0,
 *          :total_allocated_object=>7630,
 *          :total_freed_object=>88
 *      }
 *
 *  The contents of the hash are implementation specific and may be changed in
 *  the future.
 *
 *  This method is only expected to work on C Ruby.
 *
 */

static VALUE
gc_stat(int argc, VALUE *argv, VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE hash;
    static VALUE sym_count;
    static VALUE sym_heap_used, sym_heap_length, sym_heap_increment;
    static VALUE sym_heap_live_num, sym_heap_free_num, sym_heap_final_num;
    static VALUE sym_total_allocated_object, sym_total_freed_object;
    if (sym_count == 0) {
        sym_count = ID2SYM(rb_intern_const("count"));
        sym_heap_used = ID2SYM(rb_intern_const("heap_used"));
        sym_heap_length = ID2SYM(rb_intern_const("heap_length"));
        sym_heap_increment = ID2SYM(rb_intern_const("heap_increment"));
        sym_heap_live_num = ID2SYM(rb_intern_const("heap_live_num"));
        sym_heap_free_num = ID2SYM(rb_intern_const("heap_free_num"));
        sym_heap_final_num = ID2SYM(rb_intern_const("heap_final_num"));
        sym_total_allocated_object = ID2SYM(rb_intern_const("total_allocated_object"));
        sym_total_freed_object = ID2SYM(rb_intern_const("total_freed_object"));
    }

    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();
    }

    rest_sweep(objspace);

    rb_hash_aset(hash, sym_count, SIZET2NUM(objspace->count));
    /* implementation dependent counters */
    rb_hash_aset(hash, sym_heap_used, SIZET2NUM(objspace->heap.used));
    rb_hash_aset(hash, sym_heap_length, SIZET2NUM(objspace->heap.length));
    rb_hash_aset(hash, sym_heap_increment, SIZET2NUM(objspace->heap.increment));
    rb_hash_aset(hash, sym_heap_live_num, SIZET2NUM(objspace_live_num(objspace)));
    rb_hash_aset(hash, sym_heap_free_num, SIZET2NUM(objspace->heap.free_num));
    rb_hash_aset(hash, sym_heap_final_num, SIZET2NUM(objspace->heap.final_num));
    rb_hash_aset(hash, sym_total_allocated_object, SIZET2NUM(objspace->total_allocated_object_num));
    rb_hash_aset(hash, sym_total_freed_object, SIZET2NUM(objspace->total_freed_object_num));

    return hash;
}

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

static VALUE
gc_stress_get(VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    return ruby_gc_stress ? Qtrue : Qfalse;
}

/*
 *  call-seq:
 *    GC.stress = bool          -> bool
 *
 *  Updates the GC stress mode.
 *
 *  When stress mode is enabled, the GC is invoked at every GC opportunity:
 *  all memory and object allocations.
 *
 *  Enabling stress mode will degrade performance, it is only for debugging.
 */

static VALUE
gc_stress_set(VALUE self, VALUE flag)
{
    rb_objspace_t *objspace = &rb_objspace;
    rb_secure(2);
    ruby_gc_stress = RTEST(flag);
    return flag;
}

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

VALUE
rb_gc_enable(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    int old = dont_gc;

    dont_gc = FALSE;
    return old ? Qtrue : Qfalse;
}

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

VALUE
rb_gc_disable(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    int old = dont_gc;

    rest_sweep(objspace);

    dont_gc = TRUE;
    return old ? Qtrue : Qfalse;
}

void
rb_gc_set_params(void)
{
    char *malloc_limit_ptr, *heap_min_slots_ptr, *free_min_ptr;

    if (rb_safe_level() > 0) return;

    malloc_limit_ptr = getenv("RUBY_GC_MALLOC_LIMIT");
    if (malloc_limit_ptr != NULL) {
        int malloc_limit_i = atoi(malloc_limit_ptr);
        if (RTEST(ruby_verbose))
            fprintf(stderr, "malloc_limit=%d (%d)\n",
                    malloc_limit_i, initial_malloc_limit);
        if (malloc_limit_i > 0) {
            initial_malloc_limit = malloc_limit_i;
        }
    }

    heap_min_slots_ptr = getenv("RUBY_HEAP_MIN_SLOTS");
    if (heap_min_slots_ptr != NULL) {
        int heap_min_slots_i = atoi(heap_min_slots_ptr);
        if (RTEST(ruby_verbose))
            fprintf(stderr, "heap_min_slots=%d (%d)\n",
                    heap_min_slots_i, initial_heap_min_slots);
        if (heap_min_slots_i > 0) {
            initial_heap_min_slots = heap_min_slots_i;
            initial_expand_heap(&rb_objspace);
        }
    }

    free_min_ptr = getenv("RUBY_FREE_MIN");
    if (free_min_ptr != NULL) {
        int free_min_i = atoi(free_min_ptr);
        if (RTEST(ruby_verbose))
            fprintf(stderr, "free_min=%d (%d)\n", free_min_i, initial_free_min);
        if (free_min_i > 0) {
            initial_free_min = free_min_i;
        }
    }
}

void
rb_objspace_reachable_objects_from(VALUE obj, void (func)(VALUE, void *), void *data)
{
    rb_objspace_t *objspace = &rb_objspace;

    if (markable_object_p(objspace, obj)) {
        struct mark_func_data_struct mfd;
        mfd.mark_func = func;
        mfd.data = data;
        objspace->mark_func_data = &mfd;
        gc_mark_children(objspace, obj);
        objspace->mark_func_data = 0;
    }
}

/*
  ------------------------ Extended allocator ------------------------
*/

static void vm_xfree(rb_objspace_t *objspace, void *ptr);

static void *
negative_size_allocation_error_with_gvl(void *ptr)
{
    rb_raise(rb_eNoMemError, "%s", (const char *)ptr);
    return 0; /* should not be reached */
}

static void
negative_size_allocation_error(const char *msg)
{
    if (ruby_thread_has_gvl_p()) {
        rb_raise(rb_eNoMemError, "%s", msg);
    }
    else {
        if (ruby_native_thread_p()) {
            rb_thread_call_with_gvl(negative_size_allocation_error_with_gvl, (void *)msg);
        }
        else {
            fprintf(stderr, "[FATAL] %s\n", msg);
            exit(EXIT_FAILURE);
        }
    }
}

static void *
ruby_memerror_body(void *dummy)
{
    rb_memerror();
    return 0;
}

static void
ruby_memerror(void)
{
    if (ruby_thread_has_gvl_p()) {
        rb_memerror();
    }
    else {
        if (ruby_native_thread_p()) {
            rb_thread_call_with_gvl(ruby_memerror_body, 0);
        }
        else {
            /* no ruby thread */
            fprintf(stderr, "[FATAL] failed to allocate memory\n");
            exit(EXIT_FAILURE);
        }
    }
}

void
rb_memerror(void)
{
    rb_thread_t *th = GET_THREAD();
    if (!nomem_error ||
        (rb_thread_raised_p(th, RAISED_NOMEMORY) && rb_safe_level() < 4)) {
        fprintf(stderr, "[FATAL] failed to allocate memory\n");
        exit(EXIT_FAILURE);
    }
    if (rb_thread_raised_p(th, RAISED_NOMEMORY)) {
        rb_thread_raised_clear(th);
        GET_THREAD()->errinfo = nomem_error;
        JUMP_TAG(TAG_RAISE);
    }
    rb_thread_raised_set(th, RAISED_NOMEMORY);
    rb_exc_raise(nomem_error);
}

static void *
aligned_malloc(size_t alignment, size_t size)
{
    void *res;

#if defined __MINGW32__
    res = __mingw_aligned_malloc(size, alignment);
#elif defined _WIN32 && !defined __CYGWIN__
    res = _aligned_malloc(size, alignment);
#elif defined(HAVE_POSIX_MEMALIGN)
    if (posix_memalign(&res, alignment, size) == 0) {
        return res;
    }
    else {
        return NULL;
    }
#elif defined(HAVE_MEMALIGN)
    res = memalign(alignment, size);
#else
    char* aligned;
    res = malloc(alignment + size + sizeof(void*));
    aligned = (char*)res + alignment + sizeof(void*);
    aligned -= ((VALUE)aligned & (alignment - 1));
    ((void**)aligned)[-1] = res;
    res = (void*)aligned;
#endif

#if defined(_DEBUG) || defined(GC_DEBUG)
    /* alignment must be a power of 2 */
    assert((alignment - 1) & alignment == 0);
    assert(alignment % sizeof(void*) == 0);
#endif
    return res;
}

static void
aligned_free(void *ptr)
{
#if defined __MINGW32__
    __mingw_aligned_free(ptr);
#elif defined _WIN32 && !defined __CYGWIN__
    _aligned_free(ptr);
#elif defined(HAVE_MEMALIGN) || defined(HAVE_POSIX_MEMALIGN)
    free(ptr);
#else
    free(((void**)ptr)[-1]);
#endif
}

static inline size_t
vm_malloc_prepare(rb_objspace_t *objspace, size_t size)
{
    if ((ssize_t)size < 0) {
        negative_size_allocation_error("negative allocation size (or too big)");
    }
    if (size == 0) size = 1;

#if CALC_EXACT_MALLOC_SIZE
    size += sizeof(size_t);
#endif

    if ((ruby_gc_stress && !ruby_disable_gc_stress) ||
        (malloc_increase+size) > malloc_limit) {
        garbage_collect_with_gvl(objspace);
    }

    return size;
}

static inline void *
vm_malloc_fixup(rb_objspace_t *objspace, void *mem, size_t size)
{
    ATOMIC_SIZE_ADD(malloc_increase, size);

#if CALC_EXACT_MALLOC_SIZE
    ATOMIC_SIZE_ADD(objspace->malloc_params.allocated_size, size);
    ATOMIC_SIZE_INC(objspace->malloc_params.allocations);
    ((size_t *)mem)[0] = size;
    mem = (size_t *)mem + 1;
#endif

    return mem;
}

#define TRY_WITH_GC(alloc) do { \
        if (!(alloc) && \
            (!garbage_collect_with_gvl(objspace) || \
             !(alloc))) { \
            ruby_memerror(); \
        } \
    } while (0)

static void *
vm_xmalloc(rb_objspace_t *objspace, size_t size)
{
    void *mem;

    size = vm_malloc_prepare(objspace, size);
    TRY_WITH_GC(mem = malloc(size));
    return vm_malloc_fixup(objspace, mem, size);
}

static void *
vm_xrealloc(rb_objspace_t *objspace, void *ptr, size_t size)
{
    void *mem;
#if CALC_EXACT_MALLOC_SIZE
    size_t oldsize;
#endif

    if ((ssize_t)size < 0) {
        negative_size_allocation_error("negative re-allocation size");
    }

    if (!ptr) return vm_xmalloc(objspace, size);

    /*
     * The behavior of realloc(ptr, 0) is implementation defined.
     * Therefore we don't use realloc(ptr, 0) for portability reason.
     * see http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_400.htm
     */
    if (size == 0) {
        vm_xfree(objspace, ptr);
        return 0;
    }
    if (ruby_gc_stress && !ruby_disable_gc_stress)
        garbage_collect_with_gvl(objspace);

#if CALC_EXACT_MALLOC_SIZE
    size += sizeof(size_t);
    ptr = (size_t *)ptr - 1;
    oldsize = ((size_t *)ptr)[0];
#endif

    mem = realloc(ptr, size);
    if (!mem) {
        if (garbage_collect_with_gvl(objspace)) {
            mem = realloc(ptr, size);
        }
        if (!mem) {
            ruby_memerror();
        }
    }
    ATOMIC_SIZE_ADD(malloc_increase, size);

#if CALC_EXACT_MALLOC_SIZE
    ATOMIC_SIZE_ADD(objspace->malloc_params.allocated_size, size - oldsize);
    ((size_t *)mem)[0] = size;
    mem = (size_t *)mem + 1;
#endif

    return mem;
}

static void
vm_xfree(rb_objspace_t *objspace, void *ptr)
{
#if CALC_EXACT_MALLOC_SIZE
    size_t size;
    ptr = ((size_t *)ptr) - 1;
    size = ((size_t*)ptr)[0];
    if (size) {
        ATOMIC_SIZE_SUB(objspace->malloc_params.allocated_size, size);
        ATOMIC_SIZE_DEC(objspace->malloc_params.allocations);
    }
#endif

    free(ptr);
}

void *
ruby_xmalloc(size_t size)
{
    return vm_xmalloc(&rb_objspace, size);
}

static inline size_t
xmalloc2_size(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 len;
}

void *
ruby_xmalloc2(size_t n, size_t size)
{
    return vm_xmalloc(&rb_objspace, xmalloc2_size(n, size));
}

static void *
vm_xcalloc(rb_objspace_t *objspace, size_t count, size_t elsize)
{
    void *mem;
    size_t size;

    size = xmalloc2_size(count, elsize);
    size = vm_malloc_prepare(objspace, size);

    TRY_WITH_GC(mem = calloc(1, size));
    return vm_malloc_fixup(objspace, mem, size);
}

void *
ruby_xcalloc(size_t n, size_t size)
{
    return vm_xcalloc(&rb_objspace, n, size);
}

void *
ruby_xrealloc(void *ptr, size_t size)
{
    return vm_xrealloc(&rb_objspace, ptr, size);
}

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 *x)
{
    if (x)
        vm_xfree(&rb_objspace, x);
}


/* Mimic ruby_xmalloc, but need not rb_objspace.
 * should return pointer suitable for ruby_xfree
 */
void *
ruby_mimmalloc(size_t size)
{
    void *mem;
#if CALC_EXACT_MALLOC_SIZE
    size += sizeof(size_t);
#endif
    mem = malloc(size);
#if CALC_EXACT_MALLOC_SIZE
    /* set 0 for consistency of allocated_size/allocations */
    ((size_t *)mem)[0] = 0;
    mem = (size_t *)mem + 1;
#endif
    return mem;
}

#if CALC_EXACT_MALLOC_SIZE
/*
 *  call-seq:
 *     GC.malloc_allocated_size -> Integer
 *
 *  Returns the size of memory allocated by malloc().
 *
 *  Only available if ruby was built with +CALC_EXACT_MALLOC_SIZE+.
 */

static VALUE
gc_malloc_allocated_size(VALUE self)
{
    return UINT2NUM(rb_objspace.malloc_params.allocated_size);
}

/*
 *  call-seq:
 *     GC.malloc_allocations -> Integer
 *
 *  Returns the number of malloc() allocations.
 *
 *  Only available if ruby was built with +CALC_EXACT_MALLOC_SIZE+.
 */

static VALUE
gc_malloc_allocations(VALUE self)
{
    return UINT2NUM(rb_objspace.malloc_params.allocations);
}
#endif

/*
  ------------------------------ WeakMap ------------------------------
*/

struct weakmap {
    st_table *obj2wmap;         /* obj -> [ref,...] */
    st_table *wmap2obj;         /* ref -> obj */
    VALUE final;
};

static int
wmap_mark_map(st_data_t key, st_data_t val, st_data_t arg)
{
    gc_mark_ptr((rb_objspace_t *)arg, (VALUE)val);
    return ST_CONTINUE;
}

static void
wmap_mark(void *ptr)
{
    struct weakmap *w = ptr;
    st_foreach(w->obj2wmap, wmap_mark_map, (st_data_t)&rb_objspace);
    rb_gc_mark(w->final);
}

static int
wmap_free_map(st_data_t key, st_data_t val, st_data_t arg)
{
    rb_ary_resize((VALUE)val, 0);
    return ST_CONTINUE;
}

static void
wmap_free(void *ptr)
{
    struct weakmap *w = ptr;
    st_foreach(w->obj2wmap, wmap_free_map, 0);
    st_free_table(w->obj2wmap);
    st_free_table(w->wmap2obj);
}

size_t rb_ary_memsize(VALUE ary);
static int
wmap_memsize_map(st_data_t key, st_data_t val, st_data_t arg)
{
    *(size_t *)arg += rb_ary_memsize((VALUE)val);
    return ST_CONTINUE;
}

static size_t
wmap_memsize(const void *ptr)
{
    size_t size;
    const struct weakmap *w = ptr;
    if (!w) return 0;
    size = sizeof(*w);
    size += st_memsize(w->obj2wmap);
    size += st_memsize(w->wmap2obj);
    st_foreach(w->obj2wmap, wmap_memsize_map, (st_data_t)&size);
    return size;
}

static const rb_data_type_t weakmap_type = {
    "weakmap",
    {
        wmap_mark,
        wmap_free,
        wmap_memsize,
    }
};

static VALUE
wmap_allocate(VALUE klass)
{
    struct weakmap *w;
    VALUE obj = TypedData_Make_Struct(klass, struct weakmap, &weakmap_type, w);
    w->obj2wmap = st_init_numtable();
    w->wmap2obj = st_init_numtable();
    w->final = rb_obj_method(obj, ID2SYM(rb_intern("finalize")));
    return obj;
}

static int
wmap_final_func(st_data_t *key, st_data_t *value, st_data_t arg, int existing)
{
    VALUE wmap, ary;
    if (!existing) return ST_STOP;
    wmap = (VALUE)arg, ary = (VALUE)*value;
    rb_ary_delete_same(ary, wmap);
    if (!RARRAY_LEN(ary)) return ST_DELETE;
    return ST_CONTINUE;
}

static VALUE
wmap_finalize(VALUE self, VALUE objid)
{
    st_data_t orig, wmap, data;
    VALUE obj, rids;
    long i;
    struct weakmap *w;

    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
    /* Get reference from object id. */
    obj = obj_id_to_ref(objid);

    /* obj is original referenced object and/or weak reference. */
    orig = (st_data_t)obj;
    if (st_delete(w->obj2wmap, &orig, &data)) {
        rids = (VALUE)data;
        for (i = 0; i < RARRAY_LEN(rids); ++i) {
            wmap = (st_data_t)RARRAY_PTR(rids)[i];
            st_delete(w->wmap2obj, &wmap, NULL);
        }
    }

    wmap = (st_data_t)obj;
    if (st_delete(w->wmap2obj, &wmap, &orig)) {
        wmap = (st_data_t)obj;
        st_update(w->obj2wmap, orig, wmap_final_func, wmap);
    }
    return self;
}

/* Creates a weak reference from the given key to the given value */
static VALUE
wmap_aset(VALUE self, VALUE wmap, VALUE orig)
{
    st_data_t data;
    VALUE rids;
    struct weakmap *w;

    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
    rb_define_final(orig, w->final);
    rb_define_final(wmap, w->final);
    if (st_lookup(w->obj2wmap, (st_data_t)orig, &data)) {
        rids = (VALUE)data;
    }
    else {
        rids = rb_ary_tmp_new(1);
        st_insert(w->obj2wmap, (st_data_t)orig, (st_data_t)rids);
    }
    rb_ary_push(rids, wmap);
    st_insert(w->wmap2obj, (st_data_t)wmap, (st_data_t)orig);
    return nonspecial_obj_id(orig);
}

/* Retrieves a weakly referenced object with the given key */
static VALUE
wmap_aref(VALUE self, VALUE wmap)
{
    st_data_t data;
    VALUE obj;
    struct weakmap *w;
    rb_objspace_t *objspace = &rb_objspace;

    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
    if (!st_lookup(w->wmap2obj, (st_data_t)wmap, &data)) return Qnil;
    obj = (VALUE)data;
    if (!is_id_value(objspace, obj)) return Qnil;
    if (!is_live_object(objspace, obj)) return Qnil;
    return obj;
}


/*
  ------------------------------ GC profiler ------------------------------
*/

static inline void gc_prof_set_heap_info(rb_objspace_t *, gc_profile_record *);
#define GC_PROFILE_RECORD_DEFAULT_SIZE 100

static double
getrusage_time(void)
{
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_PROCESS_CPUTIME_ID)
    {
        static int try_clock_gettime = 1;
        struct timespec ts;
        if (try_clock_gettime && clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == 0) {
            return ts.tv_sec + ts.tv_nsec * 1e-9;
        }
        else {
            try_clock_gettime = 0;
        }
    }
#endif

#ifdef RUSAGE_SELF
    {
        struct rusage usage;
        struct timeval time;
        if (getrusage(RUSAGE_SELF, &usage) == 0) {
            time = usage.ru_utime;
            return time.tv_sec + time.tv_usec * 1e-6;
        }
    }
#endif

#ifdef _WIN32
    {
        FILETIME creation_time, exit_time, kernel_time, user_time;
        ULARGE_INTEGER ui;
        LONG_LONG q;
        double t;

        if (GetProcessTimes(GetCurrentProcess(),
                            &creation_time, &exit_time, &kernel_time, &user_time) != 0) {
            memcpy(&ui, &user_time, sizeof(FILETIME));
            q = ui.QuadPart / 10L;
            t = (DWORD)(q % 1000000L) * 1e-6;
            q /= 1000000L;
#ifdef __GNUC__
            t += q;
#else
            t += (double)(DWORD)(q >> 16) * (1 << 16);
            t += (DWORD)q & ~(~0 << 16);
#endif
            return t;
        }
    }
#endif

    return 0.0;
}

static inline void
gc_prof_timer_start(rb_objspace_t *objspace)
{
    if (objspace->profile.run) {
        size_t count = objspace->profile.count;

        if (!objspace->profile.record) {
            objspace->profile.size = GC_PROFILE_RECORD_DEFAULT_SIZE;
            objspace->profile.record = malloc(sizeof(gc_profile_record) * objspace->profile.size);
        }
        if (count >= objspace->profile.size) {
            objspace->profile.size += 1000;
            objspace->profile.record = realloc(objspace->profile.record, sizeof(gc_profile_record) * objspace->profile.size);
        }
        if (!objspace->profile.record) {
            rb_bug("gc_profile malloc or realloc miss");
        }
        MEMZERO(&objspace->profile.record[count], gc_profile_record, 1);
        objspace->profile.record[count].gc_time = getrusage_time();
        objspace->profile.record[objspace->profile.count].gc_invoke_time =
            objspace->profile.record[count].gc_time - objspace->profile.invoke_time;
    }
}

static inline void
gc_prof_timer_stop(rb_objspace_t *objspace, int marked)
{
    if (objspace->profile.run) {
        double gc_time = 0;
        size_t count = objspace->profile.count;
        gc_profile_record *record = &objspace->profile.record[count];

        gc_time = getrusage_time() - record->gc_time;
        if (gc_time < 0) gc_time = 0;
        record->gc_time = gc_time;
        record->is_marked = !!(marked);
        gc_prof_set_heap_info(objspace, record);
        objspace->profile.count++;
    }
}

#if !GC_PROFILE_MORE_DETAIL

static inline void
gc_prof_mark_timer_start(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_MARK_BEGIN_ENABLED()) {
        RUBY_DTRACE_GC_MARK_BEGIN();
    }
}

static inline void
gc_prof_mark_timer_stop(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_MARK_END_ENABLED()) {
        RUBY_DTRACE_GC_MARK_END();
    }
}

static inline void
gc_prof_sweep_timer_start(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_SWEEP_BEGIN_ENABLED()) {
        RUBY_DTRACE_GC_SWEEP_BEGIN();
    }
}

static inline void
gc_prof_sweep_timer_stop(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_SWEEP_END_ENABLED()) {
        RUBY_DTRACE_GC_SWEEP_END();
    }
}

static inline void
gc_prof_set_malloc_info(rb_objspace_t *objspace)
{
}

static inline void
gc_prof_set_heap_info(rb_objspace_t *objspace, gc_profile_record *record)
{
    size_t live = objspace_live_num(objspace);
    size_t total = heaps_used * HEAP_OBJ_LIMIT;

    record->heap_total_objects = total;
    record->heap_use_size = live * sizeof(RVALUE);
    record->heap_total_size = total * sizeof(RVALUE);
}

#else

static inline void
gc_prof_mark_timer_start(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_MARK_BEGIN_ENABLED()) {
        RUBY_DTRACE_GC_MARK_BEGIN();
    }
    if (objspace->profile.run) {
        size_t count = objspace->profile.count;

        objspace->profile.record[count].gc_mark_time = getrusage_time();
    }
}

static inline void
gc_prof_mark_timer_stop(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_MARK_END_ENABLED()) {
        RUBY_DTRACE_GC_MARK_END();
    }
    if (objspace->profile.run) {
        double mark_time = 0;
        size_t count = objspace->profile.count;
        gc_profile_record *record = &objspace->profile.record[count];

        mark_time = getrusage_time() - record->gc_mark_time;
        if (mark_time < 0) mark_time = 0;
        record->gc_mark_time = mark_time;
    }
}

static inline void
gc_prof_sweep_timer_start(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_SWEEP_BEGIN_ENABLED()) {
        RUBY_DTRACE_GC_SWEEP_BEGIN();
    }
    if (objspace->profile.run) {
        size_t count = objspace->profile.count;

        objspace->profile.record[count].gc_sweep_time = getrusage_time();
    }
}

static inline void
gc_prof_sweep_timer_stop(rb_objspace_t *objspace)
{
    if (RUBY_DTRACE_GC_SWEEP_END_ENABLED()) {
        RUBY_DTRACE_GC_SWEEP_END();
    }
    if (objspace->profile.run) {
        double sweep_time = 0;
        size_t count = objspace->profile.count;
        gc_profile_record *record = &objspace->profile.record[count];

        sweep_time = getrusage_time() - record->gc_sweep_time;\
        if (sweep_time < 0) sweep_time = 0;\
        record->gc_sweep_time = sweep_time;
    }
}

static inline void
gc_prof_set_malloc_info(rb_objspace_t *objspace)
{
    if (objspace->profile.run) {
        gc_profile_record *record = &objspace->profile.record[objspace->profile.count];
        if (record) {
            record->allocate_increase = malloc_increase;
            record->allocate_limit = malloc_limit;
        }
    }
}

static inline void
gc_prof_set_heap_info(rb_objspace_t *objspace, gc_profile_record *record)
{
    size_t live = objspace_live_num(objspace);
    size_t total = heaps_used * HEAP_OBJ_LIMIT;

    record->heap_use_slots = heaps_used;
    record->heap_live_objects = live;
    record->heap_free_objects = total - live;
    record->heap_total_objects = total;
    record->have_finalize = deferred_final_list ? Qtrue : Qfalse;
    record->heap_use_size = live * sizeof(RVALUE);
    record->heap_total_size = total * sizeof(RVALUE);
}

#endif /* !GC_PROFILE_MORE_DETAIL */


/*
 *  call-seq:
 *    GC::Profiler.clear          -> nil
 *
 *  Clears the GC profiler data.
 *
 */

static VALUE
gc_profile_clear(void)
{
    rb_objspace_t *objspace = &rb_objspace;

    if (GC_PROFILE_RECORD_DEFAULT_SIZE * 2 < objspace->profile.size) {
        objspace->profile.size = GC_PROFILE_RECORD_DEFAULT_SIZE * 2;
        objspace->profile.record = realloc(objspace->profile.record, sizeof(gc_profile_record) * objspace->profile.size);
        if (!objspace->profile.record) {
            rb_memerror();
        }
    }
    MEMZERO(objspace->profile.record, gc_profile_record, objspace->profile.size);
    objspace->profile.count = 0;
    return Qnil;
}

/*
 *  call-seq:
 *     GC::Profiler.raw_data    -> [Hash, ...]
 *
 *  Returns an Array of individual raw profile data Hashes ordered
 *  from earliest to latest by +:GC_INVOKE_TIME+.
 *
 *  For example:
 *
 *    [
 *      {
 *         :GC_TIME=>1.3000000000000858e-05,
 *         :GC_INVOKE_TIME=>0.010634999999999999,
 *         :HEAP_USE_SIZE=>289640,
 *         :HEAP_TOTAL_SIZE=>588960,
 *         :HEAP_TOTAL_OBJECTS=>14724,
 *         :GC_IS_MARKED=>false
 *      },
 *      # ...
 *    ]
 *
 *  The keys mean:
 *
 *  +:GC_TIME+::
 *      Time elapsed in seconds for this GC run
 *  +:GC_INVOKE_TIME+::
 *      Time elapsed in seconds from startup to when the GC was invoked
 *  +:HEAP_USE_SIZE+::
 *      Total bytes of heap used
 *  +:HEAP_TOTAL_SIZE+::
 *      Total size of heap in bytes
 *  +:HEAP_TOTAL_OBJECTS+::
 *      Total number of objects
 *  +:GC_IS_MARKED+::
 *      Returns +true+ if the GC is in mark phase
 *
 *  If ruby was built with +GC_PROFILE_MORE_DETAIL+, you will also have access
 *  to the following hash keys:
 *
 *  +:GC_MARK_TIME+::
 *  +:GC_SWEEP_TIME+::
 *  +:ALLOCATE_INCREASE+::
 *  +:ALLOCATE_LIMIT+::
 *  +:HEAP_USE_SLOTS+::
 *  +:HEAP_LIVE_OBJECTS+::
 *  +:HEAP_FREE_OBJECTS+::
 *  +:HAVE_FINALIZE+::
 *
 */

static VALUE
gc_profile_record_get(void)
{
    VALUE prof;
    VALUE gc_profile = rb_ary_new();
    size_t i;
    rb_objspace_t *objspace = (&rb_objspace);

    if (!objspace->profile.run) {
        return Qnil;
    }

    for (i =0; i < objspace->profile.count; i++) {
        prof = rb_hash_new();
        rb_hash_aset(prof, ID2SYM(rb_intern("GC_TIME")), DBL2NUM(objspace->profile.record[i].gc_time));
        rb_hash_aset(prof, ID2SYM(rb_intern("GC_INVOKE_TIME")), DBL2NUM(objspace->profile.record[i].gc_invoke_time));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_USE_SIZE")), SIZET2NUM(objspace->profile.record[i].heap_use_size));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_TOTAL_SIZE")), SIZET2NUM(objspace->profile.record[i].heap_total_size));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_TOTAL_OBJECTS")), SIZET2NUM(objspace->profile.record[i].heap_total_objects));
        rb_hash_aset(prof, ID2SYM(rb_intern("GC_IS_MARKED")), objspace->profile.record[i].is_marked);
#if GC_PROFILE_MORE_DETAIL
        rb_hash_aset(prof, ID2SYM(rb_intern("GC_MARK_TIME")), DBL2NUM(objspace->profile.record[i].gc_mark_time));
        rb_hash_aset(prof, ID2SYM(rb_intern("GC_SWEEP_TIME")), DBL2NUM(objspace->profile.record[i].gc_sweep_time));
        rb_hash_aset(prof, ID2SYM(rb_intern("ALLOCATE_INCREASE")), SIZET2NUM(objspace->profile.record[i].allocate_increase));
        rb_hash_aset(prof, ID2SYM(rb_intern("ALLOCATE_LIMIT")), SIZET2NUM(objspace->profile.record[i].allocate_limit));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_USE_SLOTS")), SIZET2NUM(objspace->profile.record[i].heap_use_slots));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_LIVE_OBJECTS")), SIZET2NUM(objspace->profile.record[i].heap_live_objects));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_FREE_OBJECTS")), SIZET2NUM(objspace->profile.record[i].heap_free_objects));
        rb_hash_aset(prof, ID2SYM(rb_intern("HAVE_FINALIZE")), objspace->profile.record[i].have_finalize);
#endif
        rb_ary_push(gc_profile, prof);
    }

    return gc_profile;
}

static void
gc_profile_dump_on(VALUE out, VALUE (*append)(VALUE, VALUE))
{
    rb_objspace_t *objspace = &rb_objspace;
    size_t count = objspace->profile.count;

    if (objspace->profile.run && count) {
        int index = 1;
        size_t i;
        gc_profile_record r;
        append(out, rb_sprintf("GC %"PRIuSIZE" invokes.\n", objspace->count));
        append(out, rb_str_new_cstr("Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC Time(ms)\n"));
        for (i = 0; i < count; i++) {
            r = objspace->profile.record[i];
#if !GC_PROFILE_MORE_DETAIL
            if (r.is_marked) {
#endif
                append(out, rb_sprintf("%5d %19.3f %20"PRIuSIZE" %20"PRIuSIZE" %20"PRIuSIZE" %30.20f\n",
                        index++, r.gc_invoke_time, r.heap_use_size,
                        r.heap_total_size, r.heap_total_objects, r.gc_time*1000));
#if !GC_PROFILE_MORE_DETAIL
            }
#endif
        }
#if GC_PROFILE_MORE_DETAIL
        append(out, rb_str_new_cstr("\n\n" \
                "More detail.\n" \
                "Index Allocate Increase    Allocate Limit  Use Slot  Have Finalize             Mark Time(ms)            Sweep Time(ms)\n"));
        index = 1;
        for (i = 0; i < count; i++) {
            r = objspace->profile.record[i];
            append(out, rb_sprintf("%5d %17"PRIuSIZE" %17"PRIuSIZE" %9"PRIuSIZE" %14s %25.20f %25.20f\n",
                        index++, r.allocate_increase, r.allocate_limit,
                        r.heap_use_slots, (r.have_finalize ? "true" : "false"),
                        r.gc_mark_time*1000, r.gc_sweep_time*1000));
        }
#endif
    }
}

/*
 *  call-seq:
 *     GC::Profiler.result  -> String
 *
 *  Returns a profile data report such as:
 *
 *    GC 1 invokes.
 *    Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC time(ms)
 *        1               0.012               159240               212940                10647         0.00000000000001530000
 */

static VALUE
gc_profile_result(void)
{
        VALUE str = rb_str_buf_new(0);
        gc_profile_dump_on(str, rb_str_buf_append);
        return str;
}

/*
 *  call-seq:
 *     GC::Profiler.report
 *     GC::Profiler.report(io)
 *
 *  Writes the GC::Profiler.result to <tt>$stdout</tt> or the given IO object.
 *
 */

static VALUE
gc_profile_report(int argc, VALUE *argv, VALUE self)
{
    VALUE out;

    if (argc == 0) {
        out = rb_stdout;
    }
    else {
        rb_scan_args(argc, argv, "01", &out);
    }
    gc_profile_dump_on(out, rb_io_write);

    return Qnil;
}

/*
 *  call-seq:
 *     GC::Profiler.total_time  -> float
 *
 *  The total time used for garbage collection in seconds
 */

static VALUE
gc_profile_total_time(VALUE self)
{
    double time = 0;
    rb_objspace_t *objspace = &rb_objspace;
    size_t i;

    if (objspace->profile.run && objspace->profile.count) {
        for (i = 0; i < objspace->profile.count; i++) {
            time += objspace->profile.record[i].gc_time;
        }
    }
    return DBL2NUM(time);
}

/*
 *  call-seq:
 *    GC::Profiler.enabled?     -> true or false
 *
 *  The current status of GC profile mode.
 */

static VALUE
gc_profile_enable_get(VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    return objspace->profile.run ? Qtrue : Qfalse;
}

/*
 *  call-seq:
 *    GC::Profiler.enable       -> nil
 *
 *  Starts the GC profiler.
 *
 */

static VALUE
gc_profile_enable(void)
{
    rb_objspace_t *objspace = &rb_objspace;

    objspace->profile.run = TRUE;
    return Qnil;
}

/*
 *  call-seq:
 *    GC::Profiler.disable      -> nil
 *
 *  Stops the GC profiler.
 *
 */

static VALUE
gc_profile_disable(void)
{
    rb_objspace_t *objspace = &rb_objspace;

    objspace->profile.run = FALSE;
    return Qnil;
}

#ifdef GC_DEBUG

/*
  ------------------------------ DEBUG ------------------------------
*/

void
rb_gcdebug_print_obj_condition(VALUE obj)
{
    rb_objspace_t *objspace = &rb_objspace;

    if (is_pointer_to_heap(objspace, (void *)obj)) {
        fprintf(stderr, "pointer to heap?: true\n");
    }
    else {
        fprintf(stderr, "pointer to heap?: false\n");
        return;
    }
    fprintf(stderr, "marked?: %s\n",
            MARKED_IN_BITMAP(GET_HEAP_BITMAP(obj), obj) ? "true" : "false");
    if (is_lazy_sweeping(objspace)) {
        fprintf(stderr, "lazy sweeping?: true\n");
        fprintf(stderr, "swept?: %s\n",
                is_swept_object(objspace, obj) ? "done" : "not yet");
    }
    else {
        fprintf(stderr, "lazy sweeping?: false\n");
    }
}

static VALUE
gcdebug_sential(VALUE obj, VALUE name)
{
    fprintf(stderr, "WARNING: object %s(%p) is inadvertently collected\n", (char *)name, (void *)obj);
    return Qnil;
}

void
rb_gcdebug_sentinel(VALUE obj, const char *name)
{
    rb_define_final(obj, rb_proc_new(gcdebug_sential, (VALUE)name));
}
#endif /* GC_DEBUG */


/*
 * Document-class: ObjectSpace
 *
 *  The ObjectSpace module contains a number of routines
 *  that interact with the garbage collection facility and allow you to
 *  traverse all living objects with an iterator.
 *
 *  ObjectSpace 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}" })
 *
 *  _produces:_
 *
 *     Finalizer three on 537763470
 *     Finalizer one on 537763480
 *     Finalizer two on 537763480
 *
 */

/*
 *  Document-class: ObjectSpace::WeakMap
 *
 *  An ObjectSpace::WeakMap object holds references to
 *  any objects, but those objects can get garbage collected.
 *
 *  This class is mostly used internally by WeakRef, please use
 *  +lib/weakref.rb+ for the public interface.
 */

/*  Document-class: GC::Profiler
 *
 *  The GC profiler provides access to information on GC runs including time,
 *  length and object space size.
 *
 *  Example:
 *
 *    GC::Profiler.enable
 *
 *    require 'rdoc/rdoc'
 *
 *    GC::Profiler.report
 *
 *    GC::Profiler.disable
 *
 *  See also GC.count, GC.malloc_allocated_size and GC.malloc_allocations
 */

/*
 *  The GC module provides an interface to Ruby's mark and
 *  sweep garbage collection mechanism.
 *
 *  Some of the underlying methods are also available via the ObjectSpace
 *  module.
 *
 *  You may obtain information about the operation of the GC through
 *  GC::Profiler.
 */

void
Init_GC(void)
{
    VALUE rb_mObSpace;
    VALUE rb_mProfiler;

    rb_mGC = rb_define_module("GC");
    rb_define_singleton_method(rb_mGC, "start", rb_gc_start, 0);
    rb_define_singleton_method(rb_mGC, "enable", rb_gc_enable, 0);
    rb_define_singleton_method(rb_mGC, "disable", rb_gc_disable, 0);
    rb_define_singleton_method(rb_mGC, "stress", gc_stress_get, 0);
    rb_define_singleton_method(rb_mGC, "stress=", gc_stress_set, 1);
    rb_define_singleton_method(rb_mGC, "count", gc_count, 0);
    rb_define_singleton_method(rb_mGC, "stat", gc_stat, -1);
    rb_define_method(rb_mGC, "garbage_collect", rb_gc_start, 0);

    rb_mProfiler = rb_define_module_under(rb_mGC, "Profiler");
    rb_define_singleton_method(rb_mProfiler, "enabled?", gc_profile_enable_get, 0);
    rb_define_singleton_method(rb_mProfiler, "enable", gc_profile_enable, 0);
    rb_define_singleton_method(rb_mProfiler, "raw_data", gc_profile_record_get, 0);
    rb_define_singleton_method(rb_mProfiler, "disable", gc_profile_disable, 0);
    rb_define_singleton_method(rb_mProfiler, "clear", gc_profile_clear, 0);
    rb_define_singleton_method(rb_mProfiler, "result", gc_profile_result, 0);
    rb_define_singleton_method(rb_mProfiler, "report", gc_profile_report, -1);
    rb_define_singleton_method(rb_mProfiler, "total_time", gc_profile_total_time, 0);

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

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

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

    nomem_error = rb_exc_new3(rb_eNoMemError,
                              rb_obj_freeze(rb_str_new2("failed to allocate memory")));
    OBJ_TAINT(nomem_error);
    OBJ_FREEZE(nomem_error);

    rb_define_method(rb_cBasicObject, "__id__", rb_obj_id, 0);
    rb_define_method(rb_mKernel, "object_id", rb_obj_id, 0);

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

    {
        VALUE rb_cWeakMap = rb_define_class_under(rb_mObSpace, "WeakMap", rb_cObject);
        rb_define_alloc_func(rb_cWeakMap, wmap_allocate);
        rb_define_method(rb_cWeakMap, "[]=", wmap_aset, 2);
        rb_define_method(rb_cWeakMap, "[]", wmap_aref, 1);
        rb_define_private_method(rb_cWeakMap, "finalize", wmap_finalize, 1);
    }

#if CALC_EXACT_MALLOC_SIZE
    rb_define_singleton_method(rb_mGC, "malloc_allocated_size", gc_malloc_allocated_size, 0);
    rb_define_singleton_method(rb_mGC, "malloc_allocations", gc_malloc_allocations, 0);
#endif
}