gc.c

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

  gc.c -

  $Author: yugui $
  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/util.h"
#include "eval_intern.h"
#include "vm_core.h"
#include "gc.h"
#include <stdio.h>
#include <setjmp.h>
#include <sys/types.h>

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

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

#if defined _WIN32 || defined __CYGWIN__
#include <windows.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

int rb_io_fptr_finalize(struct rb_io_t*);

#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 nomem_error GET_VM()->special_exceptions[ruby_error_nomemory]

#define MARK_STACK_MAX 1024

int ruby_gc_debug_indent = 0;

/* for GC profile */
#define GC_PROFILE_MORE_DETAIL 0
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;

    size_t allocate_increase;
    size_t allocate_limit;
} gc_profile_record;

static double
getrusage_time(void)
{
#ifdef RUSAGE_SELF
    struct rusage usage;
    struct timeval time;
    getrusage(RUSAGE_SELF, &usage);
    time = usage.ru_utime;
    return time.tv_sec + time.tv_usec * 1e-6;
#elif defined _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)
    {
        return 0.0;
    }
    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;
#else
    return 0.0;
#endif
}

#define GC_PROF_TIMER_START do {\
        if (objspace->profile.run) {\
            if (!objspace->profile.record) {\
                objspace->profile.size = 1000;\
                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);\
            gc_time = getrusage_time();\
            objspace->profile.record[count].gc_invoke_time = gc_time - objspace->profile.invoke_time;\
        }\
    } while(0)

#define GC_PROF_TIMER_STOP do {\
        if (objspace->profile.run) {\
            gc_time = getrusage_time() - gc_time;\
            if (gc_time < 0) gc_time = 0;\
            objspace->profile.record[count].gc_time = gc_time;\
            objspace->profile.count++;\
        }\
    } while(0)

#if GC_PROFILE_MORE_DETAIL
#define INIT_GC_PROF_PARAMS double gc_time = 0, mark_time = 0, sweep_time = 0;\
    size_t count = objspace->profile.count

#define GC_PROF_MARK_TIMER_START do {\
        if (objspace->profile.run) {\
            mark_time = getrusage_time();\
        }\
    } while(0)

#define GC_PROF_MARK_TIMER_STOP do {\
        if (objspace->profile.run) {\
            mark_time = getrusage_time() - mark_time;\
            if (mark_time < 0) mark_time = 0;\
            objspace->profile.record[count].gc_mark_time = mark_time;\
        }\
    } while(0)

#define GC_PROF_SWEEP_TIMER_START do {\
        if (objspace->profile.run) {\
            sweep_time = getrusage_time();\
        }\
    } while(0)

#define GC_PROF_SWEEP_TIMER_STOP do {\
        if (objspace->profile.run) {\
            sweep_time = getrusage_time() - sweep_time;\
            if (sweep_time < 0) sweep_time = 0;\
            objspace->profile.record[count].gc_sweep_time = sweep_time;\
        }\
    } while(0)
#define GC_PROF_SET_MALLOC_INFO do {\
        if (objspace->profile.run) {\
            gc_profile_record *record = &objspace->profile.record[objspace->profile.count];\
            record->allocate_increase = malloc_increase;\
            record->allocate_limit = malloc_limit; \
        }\
    } while(0)
#define GC_PROF_SET_HEAP_INFO do {\
        if (objspace->profile.run) {\
            gc_profile_record *record = &objspace->profile.record[objspace->profile.count];\
            record->heap_use_slots = heaps_used;\
            record->heap_live_objects = live;\
            record->heap_free_objects = freed; \
            record->heap_total_objects = heaps_used * HEAP_OBJ_LIMIT;\
            record->have_finalize = final_list ? Qtrue : Qfalse;\
            record->heap_use_size = live * sizeof(RVALUE); \
            record->heap_total_size = heaps_used * (HEAP_OBJ_LIMIT * sizeof(RVALUE));\
        }\
    } while(0)
#else
#define INIT_GC_PROF_PARAMS double gc_time = 0;\
    size_t count = objspace->profile.count
#define GC_PROF_MARK_TIMER_START
#define GC_PROF_MARK_TIMER_STOP
#define GC_PROF_SWEEP_TIMER_START
#define GC_PROF_SWEEP_TIMER_STOP
#define GC_PROF_SET_MALLOC_INFO
#define GC_PROF_SET_HEAP_INFO do {\
        if (objspace->profile.run) {\
            gc_profile_record *record = &objspace->profile.record[objspace->profile.count];\
            record->heap_total_objects = heaps_used * HEAP_OBJ_LIMIT;\
            record->heap_use_size = live * sizeof(RVALUE); \
            record->heap_total_size = heaps_used * HEAP_SIZE;\
        }\
    } while(0)
#endif


#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;
    int finalize_flag;
};

#define HEAP_MIN_SLOTS 10000
#define FREE_MIN  4096

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

#define CALC_EXACT_MALLOC_SIZE 0

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;
        size_t length;
        size_t used;
        RVALUE *freelist;
        RVALUE *range[2];
        RVALUE *freed;
    } heap;
    struct {
        int dont_gc;
        int during_gc;
    } flags;
    struct {
        st_table *table;
        RVALUE *deferred;
    } final;
    struct {
        VALUE buffer[MARK_STACK_MAX];
        VALUE *ptr;
        int overflow;
    } markstack;
    struct {
        int run;
        gc_profile_record *record;
        size_t count;
        size_t size;
        double invoke_time;
    } profile;
    struct gc_list *global_list;
    unsigned int count;
    int gc_stress;
} rb_objspace_t;

#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
#define rb_objspace (*GET_VM()->objspace)
static int ruby_initial_gc_stress = 0;
int *ruby_initial_gc_stress_ptr = &ruby_initial_gc_stress;
#else
static rb_objspace_t rb_objspace = {{GC_MALLOC_LIMIT}, {HEAP_MIN_SLOTS}};
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 heap_slots              objspace->heap.slots
#define heaps                   objspace->heap.ptr
#define heaps_length            objspace->heap.length
#define heaps_used              objspace->heap.used
#define freelist                objspace->heap.freelist
#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 finalizer_table         objspace->final.table
#define deferred_final_list     objspace->final.deferred
#define mark_stack              objspace->markstack.buffer
#define mark_stack_ptr          objspace->markstack.ptr
#define mark_stack_overflow     objspace->markstack.overflow
#define global_List             objspace->global_list
#define ruby_gc_stress          objspace->gc_stress

#define need_call_final         (finalizer_table && finalizer_table->num_entries)

static void rb_objspace_call_finalizer(rb_objspace_t *objspace);

#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 = GC_MALLOC_LIMIT;
    ruby_gc_stress = ruby_initial_gc_stress;

    return objspace;
}

void
rb_objspace_free(rb_objspace_t *objspace)
{
    rb_objspace_call_finalizer(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;
            free(list);
        }
    }
    if (heaps) {
        size_t i;
        for (i = 0; i < heaps_used; ++i) {
            free(heaps[i].membase);
        }
        free(heaps);
        heaps_used = 0;
        heaps = 0;
    }
    free(objspace);
}
#endif

/* tiny heap size */
/* 32KB */
/*#define HEAP_SIZE 0x8000 */
/* 128KB */
/*#define HEAP_SIZE 0x20000 */
/* 64KB */
/*#define HEAP_SIZE 0x10000 */
/* 16KB */
#define HEAP_SIZE 0x4000
/* 8KB */
/*#define HEAP_SIZE 0x2000 */
/* 4KB */
/*#define HEAP_SIZE 0x1000 */
/* 2KB */
/*#define HEAP_SIZE 0x800 */

#define HEAP_OBJ_LIMIT (HEAP_SIZE / sizeof(struct RVALUE))

extern VALUE rb_cMutex;
extern st_table *rb_class_tbl;

int ruby_disable_gc_stress = 0;

static void run_final(rb_objspace_t *objspace, VALUE obj);
static int garbage_collect(rb_objspace_t *objspace);

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

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);
}

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

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

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

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

/*
 *  call-seq:
 *    GC::Profiler.enable          -> nil
 *
 *  updates GC profile mode.
 *  start profiler for GC.
 *
 */

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

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

/*
 *  call-seq:
 *    GC::Profiler.disable          -> nil
 *
 *  updates GC profile mode.
 *  stop profiler for GC.
 *
 */

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

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

/*
 *  call-seq:
 *    GC::Profiler.clear          -> nil
 *
 *  clear before profile data.
 *
 */

static VALUE
gc_profile_clear(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    MEMZERO(objspace->profile.record, gc_profile_record, objspace->profile.size);
    objspace->profile.count = 0;
    return Qnil;
}

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 *
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);
        }
    }
}

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

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

    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);
    }
    mem = malloc(size);
    if (!mem) {
        if (garbage_collect_with_gvl(objspace)) {
            mem = malloc(size);
        }
        if (!mem) {
            ruby_memerror();
        }
    }
    malloc_increase += size;

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

    return mem;
}

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

    if ((ssize_t)size < 0) {
        negative_size_allocation_error("negative re-allocation size");
    }
    if (!ptr) return vm_xmalloc(objspace, size);
    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);
    objspace->malloc_params.allocated_size -= size;
    ptr = (size_t *)ptr - 1;
#endif

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

#if CALC_EXACT_MALLOC_SIZE
    objspace->malloc_params.allocated_size += size;
    ((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];
    objspace->malloc_params.allocated_size -= size;
    objspace->malloc_params.allocations--;
#endif

    free(ptr);
}

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

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

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

    return mem;
}

void *
ruby_xrealloc(void *ptr, size_t size)
{
    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);
}


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

VALUE
rb_gc_enable(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 <code>true</code> 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;

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

VALUE rb_mGC;

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;
    }
}


static void
allocate_heaps(rb_objspace_t *objspace, size_t next_heaps_length)
{
    struct heaps_slot *p;
    size_t size;

    size = next_heaps_length*sizeof(struct heaps_slot);

    if (heaps_used > 0) {
        p = (struct heaps_slot *)realloc(heaps, size);
        if (p) heaps = p;
    }
    else {
        p = heaps = (struct heaps_slot *)malloc(size);
    }

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

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

    objs = HEAP_OBJ_LIMIT;
    p = (RVALUE*)malloc(HEAP_SIZE);

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

    membase = p;
    if ((VALUE)p % sizeof(RVALUE) != 0) {
        p = (RVALUE*)((VALUE)p + sizeof(RVALUE) - ((VALUE)p % sizeof(RVALUE)));
        if ((HEAP_SIZE - HEAP_OBJ_LIMIT * sizeof(RVALUE)) < (size_t)((char*)p - (char*)membase)) {
            objs--;
        }
    }

    lo = 0;
    hi = heaps_used;
    while (lo < hi) {
        register RVALUE *mid_membase;
        mid = (lo + hi) / 2;
        mid_membase = heaps[mid].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(&heaps[hi+1], &heaps[hi], struct heaps_slot, heaps_used - hi);
    }
    heaps[hi].membase = membase;
    heaps[hi].slot = p;
    heaps[hi].limit = objs;
    heaps[hi].finalize_flag = FALSE;
    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 = freelist;
        freelist = p;
        p++;
    }
}

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

    add = HEAP_MIN_SLOTS / HEAP_OBJ_LIMIT;

    if (!add) {
        add = 1;
    }

    if ((heaps_used + add) > heaps_length) {
        allocate_heaps(objspace, heaps_used + add);
    }

    for (i = 0; i < add; i++) {
        assign_heap_slot(objspace);
    }
    heaps_inc = 0;
    objspace->profile.invoke_time = getrusage_time();
}


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_heaps(objspace, 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;
}

#define RANY(o) ((RVALUE*)(o))

static VALUE
rb_newobj_from_heap(rb_objspace_t *objspace)
{
    VALUE obj;

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

    obj = (VALUE)freelist;
    freelist = freelist->as.free.next;

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

    return obj;
}

#if USE_VALUE_CACHE
static VALUE
rb_fill_value_cache(rb_thread_t *th)
{
    rb_objspace_t *objspace = &rb_objspace;
    int i;
    VALUE rv;

    /* LOCK */
    for (i=0; i<RUBY_VM_VALUE_CACHE_SIZE; i++) {
        VALUE v = rb_newobj_from_heap(objspace);

        th->value_cache[i] = v;
        RBASIC(v)->flags = FL_MARK;
    }
    th->value_cache_ptr = &th->value_cache[0];
    rv = rb_newobj_from_heap(objspace);
    /* UNLOCK */
    return rv;
}
#endif

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

VALUE
rb_newobj(void)
{
#if USE_VALUE_CACHE || (defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE)
    rb_thread_t *th = GET_THREAD();
#endif
#if USE_VALUE_CACHE
    VALUE v = *th->value_cache_ptr;
#endif
#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
    rb_objspace_t *objspace = th->vm->objspace;
#else
    rb_objspace_t *objspace = &rb_objspace;
#endif

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

#if USE_VALUE_CACHE
    if (v) {
        RBASIC(v)->flags = 0;
        th->value_cache_ptr++;
    }
    else {
        v = rb_fill_value_cache(th);
    }

#if defined(GC_DEBUG)
    printf("cache index: %d, v: %p, th: %p\n",
           th->value_cache_ptr - th->value_cache, v, th);
#endif
    return v;
#else
    return rb_newobj_from_heap(objspace);
#endif
}

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)->dsize) {
        return RTYPEDDATA_TYPE(obj)->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;
    }
}

#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

#define GC_WATER_MARK 512

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;
}

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

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

static void
init_mark_stack(rb_objspace_t *objspace)
{
    mark_stack_overflow = 0;
    mark_stack_ptr = mark_stack;
}

#define MARK_STACK_EMPTY (mark_stack_ptr == mark_stack)

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

static void
gc_mark_all(rb_objspace_t *objspace)
{
    RVALUE *p, *pend;
    size_t i;

    init_mark_stack(objspace);
    for (i = 0; i < heaps_used; i++) {
        p = heaps[i].slot; pend = p + heaps[i].limit;
        while (p < pend) {
            if ((p->as.basic.flags & FL_MARK) &&
                (p->as.basic.flags != FL_MARK)) {
                gc_mark_children(objspace, (VALUE)p, 0);
            }
            p++;
        }
    }
}

static void
gc_mark_rest(rb_objspace_t *objspace)
{
    VALUE tmp_arry[MARK_STACK_MAX];
    VALUE *p;

    p = (mark_stack_ptr - mark_stack) + tmp_arry;
    MEMCPY(tmp_arry, mark_stack, VALUE, p - tmp_arry);

    init_mark_stack(objspace);
    while (p != tmp_arry) {
        p--;
        gc_mark_children(objspace, *p, 0);
    }
}

static inline int
is_pointer_to_heap(rb_objspace_t *objspace, void *ptr)
{
    register RVALUE *p = RANY(ptr);
    register struct 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 = &heaps[mid];
        if (heap->slot <= p) {
            if (p < heap->slot + heap->limit)
                return TRUE;
            lo = mid + 1;
        }
        else {
            hi = mid;
        }
    }
    return FALSE;
}

static void
mark_locations_array(rb_objspace_t *objspace, register VALUE *x, register long n)
{
    VALUE v;
    while (n--) {
        v = *x;
        VALGRIND_MAKE_MEM_DEFINED(&v, sizeof(v));
        if (is_pointer_to_heap(objspace, (void *)v)) {
            gc_mark(objspace, v, 0);
        }
        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;
    int lev;
};

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

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

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

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

void
rb_mark_set(st_table *tbl)
{
    mark_set(&rb_objspace, tbl, 0);
}

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

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

void
rb_mark_hash(st_table *tbl)
{
    mark_hash(&rb_objspace, tbl, 0);
}

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

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

void
rb_mark_method_entry(const rb_method_entry_t *me)
{
    mark_method_entry(&rb_objspace, me, 0);
}

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, arg->lev);
    return ST_CONTINUE;
}

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

static int
free_method_entry_i(ID key, rb_method_entry_t *me, st_data_t data)
{
    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);
}

void
rb_mark_tbl(st_table *tbl)
{
    mark_tbl(&rb_objspace, tbl, 0);
}

void
rb_gc_mark_maybe(VALUE obj)
{
    if (is_pointer_to_heap(&rb_objspace, (void *)obj)) {
        gc_mark(&rb_objspace, obj, 0);
    }
}

#define GC_LEVEL_MAX 250

static void
gc_mark(rb_objspace_t *objspace, VALUE ptr, int lev)
{
    register RVALUE *obj;

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

    if (lev > GC_LEVEL_MAX || (lev == 0 && stack_check())) {
        if (!mark_stack_overflow) {
            if (mark_stack_ptr - mark_stack < MARK_STACK_MAX) {
                *mark_stack_ptr = ptr;
                mark_stack_ptr++;
            }
            else {
                mark_stack_overflow = 1;
            }
        }
        return;
    }
    gc_mark_children(objspace, ptr, lev+1);
}

void
rb_gc_mark(VALUE ptr)
{
    gc_mark(&rb_objspace, ptr, 0);
}

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

    goto marking;               /* skip */

  again:
    obj = RANY(ptr);
    if (rb_special_const_p(ptr)) return; /* special const not marked */
    if (obj->as.basic.flags == 0) return;       /* free cell */
    if (obj->as.basic.flags & FL_MARK) return;  /* already marked */
    obj->as.basic.flags |= FL_MARK;

  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, lev);
            /* fall through */
          case NODE_BLOCK:      /* 1,3 */
          case NODE_OPTBLOCK:
          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:
          case NODE_ARGS:
            gc_mark(objspace, (VALUE)obj->as.node.u1.node, lev);
            /* 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, lev);
            /* 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, lev);
            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);
            ptr = (VALUE)obj->as.node.u2.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, lev);
            }
            if (is_pointer_to_heap(objspace, obj->as.node.u2.node)) {
                gc_mark(objspace, (VALUE)obj->as.node.u2.node, lev);
            }
            if (is_pointer_to_heap(objspace, obj->as.node.u3.node)) {
                gc_mark(objspace, (VALUE)obj->as.node.u3.node, lev);
            }
        }
        return;                 /* no need to mark class. */
    }

    gc_mark(objspace, obj->as.basic.klass, lev);
    switch (BUILTIN_TYPE(obj)) {
      case T_ICLASS:
      case T_CLASS:
      case T_MODULE:
        mark_m_tbl(objspace, RCLASS_M_TBL(obj), lev);
        mark_tbl(objspace, RCLASS_IV_TBL(obj), lev);
        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++, lev);
            }
        }
        break;

      case T_HASH:
        mark_hash(objspace, obj->as.hash.ntbl, lev);
        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)) {
            if (obj->as.typeddata.type->dmark) (*obj->as.typeddata.type->dmark)(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++, lev);
            }
        }
        break;

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

      case T_REGEXP:
        gc_mark(objspace, obj->as.regexp.src, lev);
        break;

      case T_FLOAT:
      case T_BIGNUM:
      case T_ZOMBIE:
        break;

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

      case T_RATIONAL:
        gc_mark(objspace, obj->as.rational.num, lev);
        gc_mark(objspace, obj->as.rational.den, lev);
        break;

      case T_COMPLEX:
        gc_mark(objspace, obj->as.complex.real, lev);
        gc_mark(objspace, obj->as.complex.imag, lev);
        break;

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

            while (len--) {
                gc_mark(objspace, *ptr++, lev);
            }
        }
        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 int obj_free(rb_objspace_t *, VALUE);

static inline void
add_freelist(rb_objspace_t *objspace, RVALUE *p)
{
    VALGRIND_MAKE_MEM_UNDEFINED((void*)p, sizeof(RVALUE));
    p->as.free.flags = 0;
    p->as.free.next = freelist;
    freelist = p;
}

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_freelist(objspace, p);
        }
        else {
            struct heaps_slot *slot = (struct heaps_slot *)(VALUE)RDATA(p)->dmark;
            slot->limit--;
        }
        p = tmp;
    }
}

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 (heaps[i].limit == 0) {
            if (!last) {
                last = heaps[i].membase;
            }
            else {
                free(heaps[i].membase);
            }
            heaps_used--;
        }
        else {
            if (i != j) {
                heaps[j] = heaps[i];
            }
            j++;
        }
    }
    if (last) {
        if (last < heaps_freed) {
            free(heaps_freed);
            heaps_freed = last;
        }
        else {
            free(last);
        }
    }
}

static void
gc_sweep(rb_objspace_t *objspace)
{
    RVALUE *p, *pend, *final_list;
    size_t freed = 0;
    size_t i;
    size_t live = 0, free_min = 0, do_heap_free = 0;

    do_heap_free = (size_t)((heaps_used * HEAP_OBJ_LIMIT) * 0.65);
    free_min = (size_t)((heaps_used * HEAP_OBJ_LIMIT)  * 0.2);

    if (free_min < FREE_MIN) {
        do_heap_free = heaps_used * HEAP_OBJ_LIMIT;
        free_min = FREE_MIN;
    }

    freelist = 0;
    final_list = deferred_final_list;
    deferred_final_list = 0;
    for (i = 0; i < heaps_used; i++) {
        size_t free_num = 0, final_num = 0;
        RVALUE *free = freelist;
        RVALUE *final = final_list;
        int deferred;

        if(heaps[i].finalize_flag) continue;

        p = heaps[i].slot; pend = p + heaps[i].limit;
        while (p < pend) {
            if (!(p->as.basic.flags & FL_MARK)) {
                if (p->as.basic.flags &&
                    ((deferred = obj_free(objspace, (VALUE)p)) ||
                     ((FL_TEST(p, FL_FINALIZE)) && need_call_final))) {
                    if (!deferred) {
                        p->as.free.flags = T_ZOMBIE;
                        RDATA(p)->dfree = 0;
                    }
                    p->as.free.flags |= FL_MARK;
                    p->as.free.next = final_list;
                    final_list = p;
                    final_num++;
                }
                else {
                    add_freelist(objspace, p);
                    free_num++;
                }
            }
            else if (BUILTIN_TYPE(p) == T_ZOMBIE) {
                /* objects to be finalized */
                /* do nothing remain marked */
            }
            else {
                RBASIC(p)->flags &= ~FL_MARK;
                live++;
            }
            p++;
        }
        if (final_num + free_num == heaps[i].limit && freed > do_heap_free) {
            RVALUE *pp;

            for (pp = final_list; pp != final; pp = pp->as.free.next) {
                RDATA(pp)->dmark = (void (*)())(VALUE)&heaps[i];
                pp->as.free.flags |= FL_SINGLETON; /* freeing page mark */
            }
            heaps[i].limit = final_num;
            heaps[i].finalize_flag = TRUE;
            freelist = free;    /* cancel this page from freelist */
        }
        else {
            freed += free_num;
        }
    }
    GC_PROF_SET_MALLOC_INFO;
    if (malloc_increase > malloc_limit) {
        malloc_limit += (size_t)((malloc_increase - malloc_limit) * (double)live / (live + freed));
        if (malloc_limit < GC_MALLOC_LIMIT) malloc_limit = GC_MALLOC_LIMIT;
    }
    malloc_increase = 0;
    if (freed < free_min) {
        set_heaps_increment(objspace);
        heaps_increment(objspace);
    }
    during_gc = 0;

    /* clear finalization list */
    if (final_list) {
        GC_PROF_SET_HEAP_INFO;
        deferred_final_list = final_list;
        RUBY_VM_SET_FINALIZER_INTERRUPT(GET_THREAD());
    }
    else{
        free_unused_heaps(objspace);
        GC_PROF_SET_HEAP_INFO;
    }
}

void
rb_gc_force_recycle(VALUE p)
{
    rb_objspace_t *objspace = &rb_objspace;
    add_freelist(objspace, (RVALUE *)p);
}

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);
        rb_free_m_table(RCLASS_M_TBL(obj));
        if (RCLASS_IV_TBL(obj)) {
            st_free_table(RCLASS_IV_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->dfree;
            }
            if ((long)RANY(obj)->as.data.dfree == -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_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)",
               BUILTIN_TYPE(obj), (void*)obj);
    }

    return 0;
}

#define GC_NOTIFY 0

void rb_vm_mark(void *ptr);

#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

static void
mark_current_machine_context(rb_objspace_t *objspace, rb_thread_t *th)
{
    rb_jmp_buf 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);

    SET_STACK_END;
    GET_STACK_BOUNDS(stack_start, stack_end, 1);

    mark_locations_array(objspace,
                         (VALUE*)save_regs_gc_mark,
                         sizeof(save_regs_gc_mark) / sizeof(VALUE));

    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((VALUE*)((char*)STACK_END + 2),
                         (STACK_START - STACK_END));
#endif
}

void rb_gc_mark_encodings(void);

static int
garbage_collect(rb_objspace_t *objspace)
{
    struct gc_list *list;
    rb_thread_t *th = GET_THREAD();
    INIT_GC_PROF_PARAMS;

    if (GC_NOTIFY) printf("start garbage_collect()\n");

    if (!heaps) {
        return FALSE;
    }

    if (dont_gc || during_gc) {
        if (!freelist) {
            if (!heaps_increment(objspace)) {
                set_heaps_increment(objspace);
                heaps_increment(objspace);
            }
        }
        return TRUE;
    }
    during_gc++;
    objspace->count++;

    GC_PROF_TIMER_START;
    GC_PROF_MARK_TIMER_START;
    SET_STACK_END;

    init_mark_stack(objspace);

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

    if (finalizer_table) {
        mark_tbl(objspace, finalizer_table, 0);
    }

    mark_current_machine_context(objspace, th);

    rb_gc_mark_threads();
    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, 0);

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

    rb_gc_mark_parser();

    /* gc_mark objects whose marking are not completed*/
    while (!MARK_STACK_EMPTY) {
        if (mark_stack_overflow) {
            gc_mark_all(objspace);
        }
        else {
            gc_mark_rest(objspace);
        }
    }
    GC_PROF_MARK_TIMER_STOP;

    GC_PROF_SWEEP_TIMER_START;
    gc_sweep(objspace);
    GC_PROF_SWEEP_TIMER_STOP;

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

    GC_PROF_TIMER_STOP;
    if (GC_NOTIFY) printf("end garbage_collect()\n");
    return TRUE;
}

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

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
}


/*
 *  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;
}

#undef Init_stack

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

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

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

/*
 * 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(int (*callback)(void *vstart, void *vend,
                                         size_t stride, void *d),
                         void *data)
{
    size_t i;
    RVALUE *membase = 0;
    RVALUE *pstart, *pend;
    rb_objspace_t *objspace = &rb_objspace;
    volatile VALUE v;

    i = 0;
    while (i < heaps_used) {
        while (0 < i && (uintptr_t)membase < (uintptr_t)heaps[i-1].membase)
            i--;
        while (i < heaps_used && (uintptr_t)heaps[i].membase <= (uintptr_t)membase )
            i++;
        if (heaps_used <= i)
            break;
        membase = heaps[i].membase;

        pstart = heaps[i].slot;
        pend = pstart + heaps[i].limit;

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

    return;
}

struct os_each_struct {
    size_t num;
    VALUE of;
};

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;
    volatile VALUE v;

    for (; p != pend; p++) {
        if (p->as.basic.flags) {
            switch (BUILTIN_TYPE(p)) {
              case T_NONE:
              case T_ICLASS:
              case T_NODE:
              case T_ZOMBIE:
                continue;
              case T_CLASS:
                if (FL_TEST(p, FL_SINGLETON))
                  continue;
              default:
                if (!p->as.basic.klass) continue;
                v = (VALUE)p;
                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)
{
    rb_objspace_t *objspace = &rb_objspace;
    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
    if (finalizer_table) {
        st_delete(finalizer_table, (st_data_t*)&obj, 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)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE obj, block, table;

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

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

    if (!finalizer_table) return;
    if (!FL_TEST(obj, FL_FINALIZE)) return;
    if (st_lookup(finalizer_table, obj, &table)) {
        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 objid, VALUE table)
{
    long i;
    int status;
    VALUE args[3];

    args[1] = 0;
    args[2] = (VALUE)rb_safe_level();
    if (!args[1] && RARRAY_LEN(table) > 0) {
        args[1] = rb_obj_freeze(rb_ary_new3(1, objid));
    }
    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]);
        rb_protect(run_single_final, (VALUE)args, &status);
    }
}

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

    objid = rb_obj_id(obj);     /* make obj into id */
    RBASIC(obj)->klass = 0;

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

    if (finalizer_table &&
        st_delete(finalizer_table, (st_data_t*)&obj, &table)) {
        run_finalizer(objspace, obj, objid, table);
    }
}

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

    if (p) {
        finalize_list(objspace, p);
    }
}

static void
gc_finalize_deferred(rb_objspace_t *objspace)
{
    finalize_deferred(objspace);
    free_unused_heaps(objspace);
}

void
rb_gc_finalize_deferred(void)
{
    gc_finalize_deferred(&rb_objspace);
}

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_MARK)) == FL_FINALIZE) {
        if (BUILTIN_TYPE(p) != T_ZOMBIE) {
            p->as.free.flags = FL_MARK | T_ZOMBIE; /* remain marked */
            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);
}

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

    /* run finalizers */
    if (finalizer_table) {
        do {
            /* XXX: this loop will make no sense */
            /* because mark will not be removed */
            finalize_deferred(objspace);
            mark_tbl(objspace, finalizer_table, 0);
            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;
                run_finalizer(objspace, curr->obj, rb_obj_id(curr->obj), curr->table);
                st_delete(finalizer_table, (st_data_t*)&curr->obj, 0);
                list = curr->next;
                xfree(curr);
            }
        }
        st_free_table(finalizer_table);
        finalizer_table = 0;
    }
    /* finalizers are part of garbage collection */
    during_gc++;
    /* run data object's finalizers */
    for (i = 0; i < heaps_used; i++) {
        p = heaps[i].slot; pend = p + heaps[i].limit;
        while (p < pend) {
            if (BUILTIN_TYPE(p) == T_DATA &&
                DATA_PTR(p) && RANY(p)->as.data.dfree &&
                RANY(p)->as.basic.klass != rb_cThread && RANY(p)->as.basic.klass != rb_cMutex) {
                p->as.free.flags = 0;
                if (RTYPEDDATA_P(p)) {
                    RDATA(p)->dfree = RANY(p)->as.typeddata.type->dfree;
                }
                if ((long)RANY(p)->as.data.dfree == -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);
    }
}

void
rb_gc(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    garbage_collect(objspace);
    gc_finalize_deferred(objspace);
}

/*
 *  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;
    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_pointer_to_heap(objspace, (void *)ptr) ||
        BUILTIN_TYPE(ptr) > T_FIXNUM || BUILTIN_TYPE(ptr) == T_ICLASS) {
        rb_raise(rb_eRangeError, "%p is not id value", p0);
    }
    if (BUILTIN_TYPE(ptr) == 0 || RBASIC(ptr)->klass == 0) {
        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 (TYPE(obj) == T_SYMBOL) {
        return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG;
    }
    if (SPECIAL_CONST_P(obj)) {
        return LONG2NUM((SIGNED_VALUE)obj);
    }
    return (VALUE)((SIGNED_VALUE)obj|FIXNUM_FLAG);
}

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 (TYPE(hash) != T_HASH)
            rb_raise(rb_eTypeError, "non-hash given");
    }

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

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

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

    if (hash == Qnil) {
        hash = rb_hash_new();
    }
    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;
}

/*
 *  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);
}

#if CALC_EXACT_MALLOC_SIZE
/*
 *  call-seq:
 *     GC.malloc_allocated_size -> Integer
 *
 *  The allocated size by malloc().
 *
 *  It returns the allocated size by malloc().
 */

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

/*
 *  call-seq:
 *     GC.malloc_allocations -> Integer
 *
 *  The number of allocated memory object by malloc().
 *
 *  It returns the number of allocated memory object by malloc().
 */

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

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")), rb_uint2inum(objspace->profile.record[i].heap_use_size));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_TOTAL_SIZE")), rb_uint2inum(objspace->profile.record[i].heap_total_size));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_TOTAL_OBJECTS")), rb_uint2inum(objspace->profile.record[i].heap_total_objects));
#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")), rb_uint2inum(objspace->profile.record[i].allocate_increase));
        rb_hash_aset(prof, ID2SYM(rb_intern("ALLOCATE_LIMIT")), rb_uint2inum(objspace->profile.record[i].allocate_limit));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_USE_SLOTS")), rb_uint2inum(objspace->profile.record[i].heap_use_slots));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_LIVE_OBJECTS")), rb_uint2inum(objspace->profile.record[i].heap_live_objects));
        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_FREE_OBJECTS")), rb_uint2inum(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;
}

/*
 *  call-seq:
 *     GC::Profiler.result -> string
 *
 *  Report profile data to string.
 *
 *  It returns a string 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)
{
    rb_objspace_t *objspace = &rb_objspace;
    VALUE record;
    VALUE result;
    int i;

    record = gc_profile_record_get();
    if (objspace->profile.run && objspace->profile.count) {
        result = rb_sprintf("GC %d invokes.\n", NUM2INT(gc_count(0)));
        rb_str_cat2(result, "Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC Time(ms)\n");
        for (i = 0; i < (int)RARRAY_LEN(record); i++) {
            VALUE r = RARRAY_PTR(record)[i];
            rb_str_catf(result, "%5d %19.3f %20d %20d %20d %30.20f\n",
                        i+1, NUM2DBL(rb_hash_aref(r, ID2SYM(rb_intern("GC_INVOKE_TIME")))),
                        NUM2INT(rb_hash_aref(r, ID2SYM(rb_intern("HEAP_USE_SIZE")))),
                        NUM2INT(rb_hash_aref(r, ID2SYM(rb_intern("HEAP_TOTAL_SIZE")))),
                        NUM2INT(rb_hash_aref(r, ID2SYM(rb_intern("HEAP_TOTAL_OBJECTS")))),
                        NUM2DBL(rb_hash_aref(r, ID2SYM(rb_intern("GC_TIME"))))*1000);
        }
#if GC_PROFILE_MORE_DETAIL
        rb_str_cat2(result, "\n\n");
        rb_str_cat2(result, "More detail.\n");
        rb_str_cat2(result, "Index Allocate Increase    Allocate Limit  Use Slot  Have Finalize             Mark Time(ms)            Sweep Time(ms)\n");
        for (i = 0; i < (int)RARRAY_LEN(record); i++) {
            VALUE r = RARRAY_PTR(record)[i];
            rb_str_catf(result, "%5d %17d %17d %9d %14s %25.20f %25.20f\n",
                        i+1, NUM2INT(rb_hash_aref(r, ID2SYM(rb_intern("ALLOCATE_INCREASE")))),
                        NUM2INT(rb_hash_aref(r, ID2SYM(rb_intern("ALLOCATE_LIMIT")))),
                        NUM2INT(rb_hash_aref(r, ID2SYM(rb_intern("HEAP_USE_SLOTS")))),
                        rb_hash_aref(r, ID2SYM(rb_intern("HAVE_FINALIZE")))? "true" : "false",
                        NUM2DBL(rb_hash_aref(r, ID2SYM(rb_intern("GC_MARK_TIME"))))*1000,
                        NUM2DBL(rb_hash_aref(r, ID2SYM(rb_intern("GC_SWEEP_TIME"))))*1000);
        }
#endif
    }
    else {
        result = rb_str_new2("");
    }
    return result;
}


/*
 *  call-seq:
 *     GC::Profiler.report
 *
 *  GC::Profiler.result display
 *
 */

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);
    }
    rb_io_write(out, gc_profile_result());

    return Qnil;
}

/*
 *  call-seq:
 *     GC::Profiler.total_time -> float
 *
 *  return total time that GC used. (msec)
 */

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);
}

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

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_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, "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_mKernel, "__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);

#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
}