/gc.c

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

  gc.c -

  $Author$
  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 "atomic.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) /* empty */
# define VALGRIND_MAKE_MEM_UNDEFINED(p, n) /* empty */
#endif

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

/* Make alloca work the best possible way.  */
#ifdef __GNUC__
# ifndef atarist
#  ifndef alloca
#   define alloca __builtin_alloca
#  endif
# endif /* atarist */
#else
# ifdef HAVE_ALLOCA_H
#  include <alloca.h>
# else
#  ifdef _AIX
 #pragma alloca
#  else
#   ifndef alloca /* predefined by HP cc +Olibcalls */
void *alloca ();
#   endif
#  endif /* AIX */
# endif /* HAVE_ALLOCA_H */
#endif /* __GNUC__ */

#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_mark_time;
    double gc_sweep_time;
    double gc_invoke_time;

    size_t heap_use_slots;
    size_t heap_live_objects;
    size_t heap_free_objects;
    size_t heap_total_objects;
    size_t heap_use_size;
    size_t heap_total_size;

    int have_finalize;
    int is_marked;

    size_t allocate_increase;
    size_t allocate_limit;
} 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 {
    void *membase;
    RVALUE *slot;
    size_t limit;
    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;
};

struct sorted_heaps_slot {
    RVALUE *start;
    RVALUE *end;
    struct heaps_slot *slot;
};

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 sorted_heaps_slot *sorted;
	size_t length;
	size_t used;
        struct heaps_free_bitmap *free_bitmap;
	RVALUE *range[2];
	RVALUE *freed;
	size_t live_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;
    int gc_stress;

    struct mark_func_data_struct {
	VALUE data;
	void (*mark_func)(struct rb_objspace *objspace, VALUE v);
    } *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)

#define nonspecial_obj_id(obj) (VALUE)((SIGNED_VALUE)(obj)|FIXNUM_FLAG)

#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_lazy_sweep(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 *);
static inline void gc_prof_inc_live_num(rb_objspace_t *);
static inline void gc_prof_dec_live_num(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].slot->bits);
	    aligned_free(objspace->heap.sorted[i].slot->membase);
            free(objspace->heap.sorted[i].slot);
	}
	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 sorted_heaps_slot *p;
    struct heaps_free_bitmap *bits;
    size_t size, add, i;

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

    if (heaps_used > 0) {
	p = (struct sorted_heaps_slot *)realloc(objspace->heap.sorted, size);
	if (p) objspace->heap.sorted = p;
    }
    else {
	p = objspace->heap.sorted = (struct sorted_heaps_slot *)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 = objspace->heap.sorted[mid].slot->membase;
	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 sorted_heaps_slot, heaps_used - hi);
    }
    objspace->heap.sorted[hi].slot = slot;
    objspace->heap.sorted[hi].start = p;
    objspace->heap.sorted[hi].end = (p + objs);
    heaps->membase = membase;
    heaps->slot = p;
    heaps->limit = objs;
    assert(objspace->heap.free_bitmap != NULL);
    heaps->bits = (uintptr_t *)objspace->heap.free_bitmap;
    objspace->heap.free_bitmap = objspace->heap.free_bitmap->next;
    HEAP_HEADER(membase)->base = heaps;
    HEAP_HEADER(membase)->bits = heaps->bits;
    memset(heaps->bits, 0, HEAP_BITMAP_LIMIT * sizeof(uintptr_t));
    objspace->heap.free_num += objs;
    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(ALT_STACK_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;
}

VALUE
rb_newobj(void)
{
    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_lazy_sweep(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
    gc_prof_inc_live_num(objspace);

    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 sorted_heaps_slot *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;

    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;
    RVALUE *last = 0;

    for (i = j = 1; j < heaps_used; i++) {
	if (objspace->heap.sorted[i].slot->limit == 0) {
            struct heaps_slot* h = objspace->heap.sorted[i].slot;
            ((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].slot->membase;
	    }
	    else {
		aligned_free(objspace->heap.sorted[i].slot->membase);
	    }
            free(objspace->heap.sorted[i].slot);
	    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].slot->membase)
	    i--;
	while (i < heaps_used && (uintptr_t)objspace->heap.sorted[i].slot->membase <= (uintptr_t)membase)
	    i++;
	if (heaps_used <= i)
	  break;
	membase = objspace->heap.sorted[i].slot->membase;

	pstart = objspace->heap.sorted[i].slot->slot;
	pend = pstart + objspace->heap.sorted[i].slot->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;
}

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);

    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();
    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);
    }
}

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);
	if (!FL_TEST(p, FL_SINGLETON)) { /* not freeing page */
            add_slot_local_freelist(objspace, p);
            if (!is_lazy_sweeping(objspace)) {
                gc_prof_dec_live_num(objspace);
            }
	}
	else {
	    struct heaps_slot *slot = (struct heaps_slot *)(VALUE)RDATA(p)->dmark;
	    slot->limit--;
	}
	p = tmp;
    }
}

static void
finalize_deferred(rb_objspace_t *objspace)
{
    RVALUE *p = deferred_final_list;
    deferred_final_list = 0;

    if (p) {
	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);
}

static int
chain_finalized_object(st_data_t key, st_data_t val, st_data_t arg)
{
    RVALUE *p = (RVALUE *)key, **final_list = (RVALUE **)arg;
    if ((p->as.basic.flags & FL_FINALIZE) == FL_FINALIZE &&
        !MARKED_IN_BITMAP(GET_HEAP_BITMAP(p), p)) {
	if (BUILTIN_TYPE(p) != T_ZOMBIE) {
	    p->as.free.flags = T_ZOMBIE;
	    RDATA(p)->dfree = 0;
	}
	p->as.free.next = *final_list;
	*final_list = p;
    }
    return ST_CONTINUE;
}

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 */
    do {
	finalize_deferred(objspace);
	/* mark reachable objects from finalizers */
	/* They might be not referred from any place here */
	mark_tbl(objspace, finalizer_table);
	gc_mark_stacked_objects(objspace);
	st_foreach(finalizer_table, chain_finalized_object,
		   (st_data_t)&deferred_final_list);
    } while (deferred_final_list);
    /* 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 = objspace->heap.sorted[i].end;
	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_dead_object(rb_objspace_t *objspace, VALUE ptr)
{
    struct heaps_slot *slot = objspace->heap.sweep_slots;
    if (!is_lazy_sweeping(objspace) || MARKED_IN_BITMAP(GET_HEAP_BITMAP(ptr), ptr))
	return FALSE;
    while (slot) {
	if ((VALUE)slot->slot <= ptr && ptr < (VALUE)(slot->slot + slot->limit))
	    return TRUE;
	slot = slot->next;
    }
    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 = objid ^ FIXNUM_FLAG;	/* unset FIXNUM_FLAG */

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

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

VALUE
rb_obj_id(VALUE obj)
{
    /*
     *                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 as:
 *  {:TOTAL=>10000, :FREE=>3011, :T_OBJECT=>6, :T_CLASS=>404, ...}
 *
 *  If the optional argument, result_hash, is given,
 *  it is overwritten and returned.
 *  This is intended to avoid probe effect.
 *
 *  The contents of the returned hash is implementation defined.
 *  It may be changed in future.
 *
 *  This method is not expected to work except C Ruby.
 *
 */

static VALUE
count_objects(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 = objspace->heap.sorted[i].end;
        for (;p < pend; p++) {
            if (p->as.basic.flags) {
                counts[BUILTIN_TYPE(p)]++;
            }
            else {
                freed++;
            }
        }
        total += objspace->heap.sorted[i].slot->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(GET_HEAP_BITMAP(slot->slot), 0,
           HEAP_BITMAP_LIMIT * sizeof(uintptr_t));
}

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

    p = sweep_slot->slot; pend = p + sweep_slot->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 {
                    VALGRIND_MAKE_MEM_UNDEFINED((void*)p, sizeof(RVALUE));
                    p->as.free.flags = 0;
                    p->as.free.next = sweep_slot->freelist;
                    sweep_slot->freelist = p;
                    free_num++;
                }
            }
            else {
                free_num++;
            }
        }
        p++;
    }
    gc_clear_slot_bits(sweep_slot);
    if (final_num + free_num == sweep_slot->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->limit = final_num;
        unlink_heap_slot(objspace, sweep_slot);
    }
    else {
        if (free_num > 0) {
            link_free_heap_slot(objspace, sweep_slot);
        }
        else {
            sweep_slot->free_next = NULL;
        }
        objspace->heap.free_num += free_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.do_heap_free = heaps_used * HEAP_OBJ_LIMIT;
        objspace->heap.free_min = 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.live_num / (heaps_used * HEAP_OBJ_LIMIT));
	…