gc.c

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

  gc.c -

  $Author: akr $
  $Date: 2005/12/16 04:58:51 $
  created at: Tue Oct  5 09:44:46 JST 1993

  Copyright (C) 1993-2003 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

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

#include "ruby.h"
#include "rubysig.h"
#include "st.h"
#include "node.h"
#include "env.h"
#include "re.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

#ifdef __ia64__
#include <ucontext.h>
#if defined(__FreeBSD__)
/*
 * FreeBSD/ia64 currently does not have a way for a process to get the
 * base address for the RSE backing store, so hardcode it.
 */
#define __libc_ia64_register_backing_store_base (4ULL<<61)
#else
#pragma weak __libc_ia64_register_backing_store_base
extern unsigned long __libc_ia64_register_backing_store_base;
#endif
#endif

#if defined _WIN32 || defined __CYGWIN__
#include <windows.h>
#endif

void re_free_registers (struct re_registers*);
void rb_io_fptr_finalize (struct OpenFile*);

#if !defined(setjmp) && defined(HAVE__SETJMP)
#define setjmp(env) _setjmp(env)
#endif

/* 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
#if defined(MSDOS) || defined(__human68k__)
#define GC_MALLOC_LIMIT 200000
#else
#define GC_MALLOC_LIMIT 8000000
#endif
#endif

static unsigned long malloc_increase = 0;
static unsigned long malloc_limit = GC_MALLOC_LIMIT;
static void run_final();
static VALUE nomem_error;
static void garbage_collect();

void
rb_memerror()
{
    static int recurse = 0;

    if (recurse > 0 && rb_safe_level() < 4) {
        fprintf(stderr, "[FATAL] failed to allocate memory\n");
        exit(1);
    }
    recurse++;
    rb_exc_raise(nomem_error);
}

void *
ruby_xmalloc(size)
    long size;
{
    void *mem;

    if (size < 0) {
        rb_raise(rb_eNoMemError, "negative allocation size (or too big)");
    }
    if (size == 0) size = 1;
    malloc_increase += size;

    if (malloc_increase > malloc_limit) {
        garbage_collect();
    }
    RUBY_CRITICAL(mem = malloc(size));
    if (!mem) {
        garbage_collect();
        RUBY_CRITICAL(mem = malloc(size));
        if (!mem) {
            rb_memerror();
        }
    }

    return mem;
}

void *
ruby_xcalloc(n, size)
    long n, size;
{
    void *mem;

    mem = xmalloc(n * size);
    memset(mem, 0, n * size);

    return mem;
}

void *
ruby_xrealloc(ptr, size)
    void *ptr;
    long size;
{
    void *mem;

    if (size < 0) {
        rb_raise(rb_eArgError, "negative re-allocation size");
    }
    if (!ptr) return xmalloc(size);
    if (size == 0) size = 1;
    malloc_increase += size;
    RUBY_CRITICAL(mem = realloc(ptr, size));
    if (!mem) {
        garbage_collect();
        RUBY_CRITICAL(mem = realloc(ptr, size));
        if (!mem) {
            rb_memerror();
        }
    }

    return mem;
}

void
ruby_xfree(x)
    void *x;
{
    if (x)
        RUBY_CRITICAL(free(x));
}

extern int ruby_in_compile;
static int dont_gc;
static int during_gc;
static int need_call_final = 0;
static st_table *finalizer_table = 0;


/*
 *  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()
{
    int old = dont_gc;

    dont_gc = Qfalse;
    return old;
}

/*
 *  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()
{
    int old = dont_gc;

    dont_gc = Qtrue;
    return old;
}

VALUE rb_mGC;

static struct gc_list {
    VALUE *varptr;
    struct gc_list *next;
} *global_List = 0;

void
rb_gc_register_address(addr)
    VALUE *addr;
{
    struct gc_list *tmp;

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

void
rb_gc_unregister_address(addr)
    VALUE *addr;
{
    struct gc_list *tmp = global_List;

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

            tmp->next = tmp->next->next;
            RUBY_CRITICAL(free(t));
            break;
        }
        tmp = tmp->next;
    }
}

#undef GC_DEBUG

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

typedef struct RVALUE {
    union {
        struct {
            unsigned long 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 RStruct rstruct;
        struct RBignum bignum;
        struct RFile   file;
        struct RNode   node;
        struct RMatch  match;
        struct RVarmap varmap;
        struct SCOPE   scope;
    } as;
#ifdef GC_DEBUG
    char *file;
    int   line;
#endif
} RVALUE;

static RVALUE *freelist = 0;
static RVALUE *deferred_final_list = 0;

#define HEAPS_INCREMENT 10
static struct heaps_slot {
    RVALUE *slot;
    int limit;
} *heaps;
static int heaps_length = 0;
static int heaps_used   = 0;

#define HEAP_MIN_SLOTS 10000
static int heap_slots = HEAP_MIN_SLOTS;

#define FREE_MIN  4096

static RVALUE *himem, *lomem;

static void
add_heap()
{
    RVALUE *p, *pend;

    if (heaps_used == heaps_length) {
        /* Realloc heaps */
        struct heaps_slot *p;
        int length;

        heaps_length += HEAPS_INCREMENT;
        length = heaps_length*sizeof(struct heaps_slot);
        RUBY_CRITICAL(
            if (heaps_used > 0) {
                p = (struct heaps_slot *)realloc(heaps, length);
                if (p) heaps = p;
            }
            else {
                p = heaps = (struct heaps_slot *)malloc(length);
            });
        if (p == 0) rb_memerror();
    }

    for (;;) {
        RUBY_CRITICAL(p = heaps[heaps_used].slot = (RVALUE*)malloc(sizeof(RVALUE)*heap_slots));
        heaps[heaps_used].limit = heap_slots;
        if (p == 0) {
            if (heap_slots == HEAP_MIN_SLOTS) {
                rb_memerror();
            }
            heap_slots = HEAP_MIN_SLOTS;
            continue;
        }
        break;
    }
    pend = p + heap_slots;
    if (lomem == 0 || lomem > p) lomem = p;
    if (himem < pend) himem = pend;
    heaps_used++;
    heap_slots *= 1.8;

    while (p < pend) {
        p->as.free.flags = 0;
        p->as.free.next = freelist;
        freelist = p;
        p++;
    }
}
#define RANY(o) ((RVALUE*)(o))

VALUE
rb_newobj()
{
    VALUE obj;

    if (!freelist) garbage_collect();

    obj = (VALUE)freelist;
    freelist = freelist->as.free.next;
    MEMZERO((void*)obj, RVALUE, 1);
#ifdef GC_DEBUG
    RANY(obj)->file = ruby_sourcefile;
    RANY(obj)->line = ruby_sourceline;
#endif
    return obj;
}

VALUE
rb_data_object_alloc(klass, datap, dmark, dfree)
    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;
}

extern st_table *rb_class_tbl;
VALUE *rb_gc_stack_start = 0;

#ifdef DJGPP
/* set stack size (http://www.delorie.com/djgpp/v2faq/faq15_9.html) */
unsigned int _stklen = 0x180000; /* 1.5 kB */
#endif

#if defined(DJGPP) || defined(_WIN32_WCE)
static unsigned int STACK_LEVEL_MAX = 65535;
#elif defined(__human68k__)
unsigned int _stacksize = 262144;
# define STACK_LEVEL_MAX (_stacksize - 4096)
# undef HAVE_GETRLIMIT
#elif defined(HAVE_GETRLIMIT)
static unsigned int STACK_LEVEL_MAX = 655300;
#else
# define STACK_LEVEL_MAX 655300
#endif

#ifdef C_ALLOCA
# define SET_STACK_END VALUE stack_end; alloca(0);
# define STACK_END (&stack_end)
#else
# if defined(__GNUC__) && defined(USE_BUILTIN_FRAME_ADDRESS) && !defined(__ia64__)
#  if ( __GNUC__ == 3 && __GNUC_MINOR__ > 0 ) || __GNUC__ > 3
__attribute__ ((noinline))
#  endif
static VALUE *
stack_end_address(void)
{
    return (VALUE *)__builtin_frame_address(0);
}
#  define  SET_STACK_END    VALUE *stack_end = stack_end_address()
# else
#  define  SET_STACK_END    VALUE *stack_end = alloca(1)
# endif
# define STACK_END (stack_end)
#endif
#if defined(sparc) || defined(__sparc__)
# define STACK_LENGTH  (rb_gc_stack_start - STACK_END + 0x80)
#elif STACK_GROW_DIRECTION < 0
# define STACK_LENGTH  (rb_gc_stack_start - STACK_END)
#elif STACK_GROW_DIRECTION > 0
# define STACK_LENGTH  (STACK_END - rb_gc_stack_start + 1)
#else
# define STACK_LENGTH  ((STACK_END < rb_gc_stack_start) ? rb_gc_stack_start - STACK_END\
                                           : STACK_END - rb_gc_stack_start + 1)
#endif
#if STACK_GROW_DIRECTION > 0
# define STACK_UPPER(x, a, b) a
#elif STACK_GROW_DIRECTION < 0
# define STACK_UPPER(x, a, b) b
#else
static int grow_direction;
static int
stack_grow_direction(addr)
    VALUE *addr;
{
    SET_STACK_END;

    if (STACK_END > addr) return grow_direction = 1;
    return grow_direction = -1;
}
# define stack_growup_p(x) ((grow_direction ? grow_direction : stack_grow_direction(x)) > 0)
# define STACK_UPPER(x, a, b) (stack_growup_p(x) ? a : b)
#endif

#define GC_WATER_MARK 512

#define CHECK_STACK(ret) do {\
    SET_STACK_END;\
    (ret) = (STACK_LENGTH > STACK_LEVEL_MAX + GC_WATER_MARK);\
} while (0)

int
ruby_stack_length(p)
    VALUE **p;
{
    SET_STACK_END;
    if (p) *p = STACK_UPPER(STACK_END, rb_gc_stack_start, STACK_END);
    return STACK_LENGTH;
}

int
ruby_stack_check()
{
    int ret;

    CHECK_STACK(ret);
    return ret;
}

#define MARK_STACK_MAX 1024
static VALUE mark_stack[MARK_STACK_MAX];
static VALUE *mark_stack_ptr;
static int mark_stack_overflow;

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

#define MARK_STACK_EMPTY (mark_stack_ptr == mark_stack)
            
static st_table *source_filenames;

char *
rb_source_filename(f)
    const char *f;
{
    char *name;

    if (!st_lookup(source_filenames, (st_data_t)f, (st_data_t *)&name)) {
        long len = strlen(f) + 1;
        char *ptr = name = ALLOC_N(char, len + 1);
        *ptr++ = 0;
        MEMCPY(ptr, f, char, len);
        st_add_direct(source_filenames, (st_data_t)ptr, (st_data_t)name);
        return ptr;
    }
    return name + 1;
}

static void
mark_source_filename(f)
    char *f;
{
    if (f) {
        f[-1] = 1;
    }
}

static int
sweep_source_filename(key, value)
    char *key, *value;
{
    if (*value) {
        *value = 0;
        return ST_CONTINUE;
    }
    else {
        free(value);
        return ST_DELETE;
    }
}

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

static void
gc_mark_all()
{
    RVALUE *p, *pend;
    int i;

    init_mark_stack();
    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((VALUE)p, 0);
            }
            p++;
        }
    }
}

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

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

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

static inline int
is_pointer_to_heap(ptr)
    void *ptr;
{
    register RVALUE *p = RANY(ptr);
    register RVALUE *heap_org;
    register long i;

    if (p < lomem || p > himem) return Qfalse;

    /* check if p looks like a pointer */
    for (i=0; i < heaps_used; i++) {
        heap_org = heaps[i].slot;
        if (heap_org <= p && p < heap_org + heaps[i].limit &&
            ((((char*)p)-((char*)heap_org))%sizeof(RVALUE)) == 0)
            return Qtrue;
    }
    return Qfalse;
}

static void
mark_locations_array(x, n)
    register VALUE *x;
    register long n;
{
    VALUE v;
    while (n--) {
        v = *x;
        if (is_pointer_to_heap((void *)v)) {
            gc_mark(v, 0);
        }
        x++;
    }
}

void
rb_gc_mark_locations(start, end)
    VALUE *start, *end;
{
    long n;

    n = end - start;
    mark_locations_array(start,n);
}

static int
mark_entry(key, value, lev)
    ID key;
    VALUE value;
    int lev;
{
    gc_mark(value, lev);
    return ST_CONTINUE;
}

static void
mark_tbl(tbl, lev)
    st_table *tbl;
    int lev;
{
    if (!tbl) return;
    st_foreach(tbl, mark_entry, lev);
}

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

static int
mark_keyvalue(key, value, lev)
    VALUE key;
    VALUE value;
    int lev;
{
    gc_mark(key, lev);
    gc_mark(value, lev);
    return ST_CONTINUE;
}

static void
mark_hash(tbl, lev)
    st_table *tbl;
    int lev;
{
    if (!tbl) return;
    st_foreach(tbl, mark_keyvalue, lev);
}

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

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

#define GC_LEVEL_MAX 250

static void
gc_mark(ptr, lev)
    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 && ruby_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(ptr, lev+1);
}

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

static void
gc_mark_children(ptr, lev)
    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 (obj->as.basic.flags & T_MASK) {
      case T_NIL:
      case T_FIXNUM:
        rb_bug("rb_gc_mark() called for broken object");
        break;

      case T_NODE:
        mark_source_filename(obj->as.node.nd_file);
        switch (nd_type(obj)) {
          case NODE_IF:         /* 1,2,3 */
          case NODE_FOR:
          case NODE_ITER:
          case NODE_CREF:
          case NODE_WHEN:
          case NODE_MASGN:
          case NODE_RESCUE:
          case NODE_RESBODY:
          case NODE_CLASS:
            gc_mark((VALUE)obj->as.node.u2.node, lev);
            /* fall through */
          case NODE_BLOCK:      /* 1,3 */
          case NODE_ARRAY:
          case NODE_DSTR:
          case NODE_DXSTR:
          case NODE_DREGX:
          case NODE_DREGX_ONCE:
          case NODE_FBODY:
          case NODE_ENSURE:
          case NODE_CALL:
          case NODE_DEFS:
          case NODE_OP_ASGN1:
            gc_mark((VALUE)obj->as.node.u1.node, lev);
            /* fall through */
          case NODE_SUPER:      /* 3 */
          case NODE_FCALL:
          case NODE_DEFN:
          case NODE_NEWLINE:
            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:
            gc_mark((VALUE)obj->as.node.u1.node, lev);
            /* fall through */
          case NODE_METHOD:     /* 2 */
          case NODE_NOT:
          case NODE_GASGN:
          case NODE_LASGN:
          case NODE_DASGN:
          case NODE_DASGN_CURR:
          case NODE_IASGN:
          case NODE_CVDECL:
          case NODE_CVASGN:
          case NODE_COLON3:
          case NODE_OPT_N:
          case NODE_EVSTR:
            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_ARGS:
          case NODE_SPLAT:
          case NODE_TO_ARY:
          case NODE_SVALUE:
            ptr = (VALUE)obj->as.node.u1.node;
            goto again;

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

          case NODE_ZARRAY:     /* - */
          case NODE_ZSUPER:
          case NODE_CFUNC:
          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_ALIAS:
          case NODE_VALIAS:
          case NODE_REDO:
          case NODE_RETRY:
          case NODE_UNDEF:
          case NODE_SELF:
          case NODE_NIL:
          case NODE_TRUE:
          case NODE_FALSE:
          case NODE_ATTRSET:
          case NODE_BLOCK_ARG:
          case NODE_POSTEXE:
            break;
          case NODE_ALLOCA:
            mark_locations_array((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(obj->as.node.u1.node)) {
                gc_mark((VALUE)obj->as.node.u1.node, lev);
            }
            if (is_pointer_to_heap(obj->as.node.u2.node)) {
                gc_mark((VALUE)obj->as.node.u2.node, lev);
            }
            if (is_pointer_to_heap(obj->as.node.u3.node)) {
                gc_mark((VALUE)obj->as.node.u3.node, lev);
            }
        }
        return;                 /* no need to mark class. */
    }

    gc_mark(obj->as.basic.klass, lev);
    switch (obj->as.basic.flags & T_MASK) {
      case T_ICLASS:
      case T_CLASS:
      case T_MODULE:
        mark_tbl(obj->as.klass.m_tbl, lev);
        mark_tbl(obj->as.klass.iv_tbl, lev);
        ptr = obj->as.klass.super;
        goto again;

      case T_ARRAY:
        if (FL_TEST(obj, ELTS_SHARED)) {
            ptr = obj->as.array.aux.shared;
            goto again;
        }
        else {
            long i, len = obj->as.array.len;
            VALUE *ptr = obj->as.array.ptr;

            for (i=0; i < len; i++) {
                gc_mark(*ptr++, lev);
            }
        }
        break;

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

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

      case T_DATA:
        if (obj->as.data.dmark) (*obj->as.data.dmark)(DATA_PTR(obj));
        break;

      case T_OBJECT:
        mark_tbl(obj->as.object.iv_tbl, lev);
        break;

      case T_FILE:
      case T_REGEXP:
      case T_FLOAT:
      case T_BIGNUM:
      case T_BLKTAG:
        break;

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

      case T_VARMAP:
        gc_mark(obj->as.varmap.val, lev);
        ptr = (VALUE)obj->as.varmap.next;
        goto again;

      case T_SCOPE:
        if (obj->as.scope.local_vars && (obj->as.scope.flags & SCOPE_MALLOC)) {
            int n = obj->as.scope.local_tbl[0]+1;
            VALUE *vars = &obj->as.scope.local_vars[-1];

            while (n--) {
                gc_mark(*vars++, lev);
            }
        }
        break;

      case T_STRUCT:
        {
            long len = obj->as.rstruct.len;
            VALUE *ptr = obj->as.rstruct.ptr;

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

      default:
        rb_bug("rb_gc_mark(): unknown data type 0x%lx(0x%lx) %s",
               obj->as.basic.flags & T_MASK, obj,
               is_pointer_to_heap(obj) ? "corrupted object" : "non object");
    }
}

static void obj_free (VALUE);

static void
finalize_list(p)
    RVALUE *p;
{
    while (p) {
        RVALUE *tmp = p->as.free.next;
        run_final((VALUE)p);
        if (!FL_TEST(p, FL_SINGLETON)) { /* not freeing page */
            p->as.free.flags = 0;
            p->as.free.next = freelist;
            freelist = p;
        }
        p = tmp;
    }
}

static void
free_unused_heaps()
{
    int i, j;

    for (i = j = 1; j < heaps_used; i++) {
        if (heaps[i].limit == 0) {
            free(heaps[i].slot);
            heaps_used--;
        }
        else {
            if (i != j) {
                heaps[j] = heaps[i];
            }
            j++;
        }
    }
}

static void
gc_sweep()
{
    RVALUE *p, *pend, *final_list;
    int freed = 0;
    int i;
    unsigned long live = 0;

    if (ruby_in_compile && ruby_parser_stack_on_heap()) {
        /* should not reclaim nodes during compilation
           if yacc's semantic stack is not allocated on machine stack */
        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) && BUILTIN_TYPE(p) == T_NODE)
                    gc_mark((VALUE)p, 0);
                p++;
            }
        }
    }

    mark_source_filename(ruby_sourcefile);
    if (source_filenames) {
        st_foreach(source_filenames, sweep_source_filename, 0);
    }

    freelist = 0;
    final_list = deferred_final_list;
    deferred_final_list = 0;
    for (i = 0; i < heaps_used; i++) {
        int n = 0;
        RVALUE *free = freelist;
        RVALUE *final = final_list;

        p = heaps[i].slot; pend = p + heaps[i].limit;
        while (p < pend) {
            if (!(p->as.basic.flags & FL_MARK)) {
                if (p->as.basic.flags) {
                    obj_free((VALUE)p);
                }
                if (need_call_final && FL_TEST(p, FL_FINALIZE)) {
                    p->as.free.flags = FL_MARK; /* remain marked */
                    p->as.free.next = final_list;
                    final_list = p;
                }
                else {
                    p->as.free.flags = 0;
                    p->as.free.next = freelist;
                    freelist = p;
                }
                n++;
            }
            else if (RBASIC(p)->flags == FL_MARK) {
                /* objects to be finalized */
                /* do notning remain marked */
            }
            else {
                RBASIC(p)->flags &= ~FL_MARK;
                live++;
            }
            p++;
        }
        if (n == heaps[i].limit && freed > FREE_MIN) {
            RVALUE *pp;

            heaps[i].limit = 0;
            for (pp = final_list; pp != final; pp = pp->as.free.next) {
                p->as.free.flags |= FL_SINGLETON; /* freeing page mark */
            }
            freelist = free;    /* cancel this page from freelist */
        }
        else {
            freed += n;
        }
    }
    if (malloc_increase > malloc_limit) {
        malloc_limit += (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) {
        add_heap();
    }
    during_gc = 0;

    /* clear finalization list */
    if (final_list) {
        deferred_final_list = final_list;
        return;
    }
    free_unused_heaps();
}

void
rb_gc_force_recycle(p)
    VALUE p;
{
    RANY(p)->as.free.flags = 0;
    RANY(p)->as.free.next = freelist;
    freelist = RANY(p);
}

static void
obj_free(obj)
    VALUE obj;
{
    switch (RANY(obj)->as.basic.flags & T_MASK) {
      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);
    }

    switch (RANY(obj)->as.basic.flags & T_MASK) {
      case T_OBJECT:
        if (RANY(obj)->as.object.iv_tbl) {
            st_free_table(RANY(obj)->as.object.iv_tbl);
        }
        break;
      case T_MODULE:
      case T_CLASS:
        rb_clear_cache_by_class((VALUE)obj);
        st_free_table(RANY(obj)->as.klass.m_tbl);
        if (RANY(obj)->as.object.iv_tbl) {
            st_free_table(RANY(obj)->as.object.iv_tbl);
        }
        break;
      case T_STRING:
        if (RANY(obj)->as.string.ptr && !FL_TEST(obj, ELTS_SHARED)) {
            RUBY_CRITICAL(free(RANY(obj)->as.string.ptr));
        }
        break;
      case T_ARRAY:
        if (RANY(obj)->as.array.ptr && !FL_TEST(obj, ELTS_SHARED)) {
            RUBY_CRITICAL(free(RANY(obj)->as.array.ptr));
        }
        break;
      case T_HASH:
        if (RANY(obj)->as.hash.tbl) {
            st_free_table(RANY(obj)->as.hash.tbl);
        }
        break;
      case T_REGEXP:
        if (RANY(obj)->as.regexp.ptr) {
            re_free_pattern(RANY(obj)->as.regexp.ptr);
        }
        if (RANY(obj)->as.regexp.str) {
            RUBY_CRITICAL(free(RANY(obj)->as.regexp.str));
        }
        break;
      case T_DATA:
        if (DATA_PTR(obj)) {
            if ((long)RANY(obj)->as.data.dfree == -1) {
                RUBY_CRITICAL(free(DATA_PTR(obj)));
            }
            else if (RANY(obj)->as.data.dfree) {
                (*RANY(obj)->as.data.dfree)(DATA_PTR(obj));
            }
        }
        break;
      case T_MATCH:
        if (RANY(obj)->as.match.regs) {
            re_free_registers(RANY(obj)->as.match.regs);
            RUBY_CRITICAL(free(RANY(obj)->as.match.regs));
        }
        break;
      case T_FILE:
        if (RANY(obj)->as.file.fptr) {
            rb_io_fptr_finalize(RANY(obj)->as.file.fptr);
            RUBY_CRITICAL(free(RANY(obj)->as.file.fptr));
        }
        break;
      case T_ICLASS:
        /* iClass shares table with the module */
        break;

      case T_FLOAT:
      case T_VARMAP:
      case T_BLKTAG:
        break;

      case T_BIGNUM:
        if (RANY(obj)->as.bignum.digits) {
            RUBY_CRITICAL(free(RANY(obj)->as.bignum.digits));
        }
        break;
      case T_NODE:
        switch (nd_type(obj)) {
          case NODE_SCOPE:
            if (RANY(obj)->as.node.u1.tbl) {
                RUBY_CRITICAL(free(RANY(obj)->as.node.u1.tbl));
            }
            break;
          case NODE_ALLOCA:
            RUBY_CRITICAL(free(RANY(obj)->as.node.u1.node));
            break;
        }
        return;                 /* no need to free iv_tbl */

      case T_SCOPE:
        if (RANY(obj)->as.scope.local_vars &&
            RANY(obj)->as.scope.flags != SCOPE_ALLOCA) {
            VALUE *vars = RANY(obj)->as.scope.local_vars-1;
            if (vars[0] == 0)
                RUBY_CRITICAL(free(RANY(obj)->as.scope.local_tbl));
            if (RANY(obj)->as.scope.flags & SCOPE_MALLOC)
                RUBY_CRITICAL(free(vars));
        }
        break;

      case T_STRUCT:
        if (RANY(obj)->as.rstruct.ptr) {
            RUBY_CRITICAL(free(RANY(obj)->as.rstruct.ptr));
        }
        break;

      default:
        rb_bug("gc_sweep(): unknown data type 0x%lx(0x%lx)",
               RANY(obj)->as.basic.flags & T_MASK, obj);
    }
}

void
rb_gc_mark_frame(frame)
    struct FRAME *frame;
{
    mark_locations_array(frame->argv, frame->argc);
    gc_mark((VALUE)frame->node, 0);
}

#ifdef __GNUC__
#if defined(__human68k__) || defined(DJGPP)
#if defined(__human68k__)
typedef unsigned long rb_jmp_buf[8];
__asm__ (".even\n\
_rb_setjmp:\n\
        move.l  4(sp),a0\n\
        movem.l d3-d7/a3-a5,(a0)\n\
        moveq.l #0,d0\n\
        rts");
#ifdef setjmp
#undef setjmp
#endif
#else
#if defined(DJGPP)
typedef unsigned long rb_jmp_buf[6];
__asm__ (".align 4\n\
_rb_setjmp:\n\
        pushl   %ebp\n\
        movl    %esp,%ebp\n\
        movl    8(%ebp),%ebp\n\
        movl    %eax,(%ebp)\n\
        movl    %ebx,4(%ebp)\n\
        movl    %ecx,8(%ebp)\n\
        movl    %edx,12(%ebp)\n\
        movl    %esi,16(%ebp)\n\
        movl    %edi,20(%ebp)\n\
        popl    %ebp\n\
        xorl    %eax,%eax\n\
        ret");
#endif
#endif
int rb_setjmp (rb_jmp_buf);
#define jmp_buf rb_jmp_buf
#define setjmp rb_setjmp
#endif /* __human68k__ or DJGPP */
#endif /* __GNUC__ */

static void
garbage_collect()
{
    struct gc_list *list;
    struct FRAME * volatile frame; /* gcc 2.7.2.3 -O2 bug??  */
    jmp_buf save_regs_gc_mark;
    SET_STACK_END;

#ifdef HAVE_NATIVETHREAD
    if (!is_ruby_native_thread()) {
        rb_bug("cross-thread violation on rb_gc()");
    }
#endif
    if (dont_gc || during_gc) {
        if (!freelist) {
            add_heap();
        }
        return;
    }
    if (during_gc) return;
    during_gc++;

    init_mark_stack();

    /* mark frame stack */
    for (frame = ruby_frame; frame; frame = frame->prev) {
        rb_gc_mark_frame(frame);
        if (frame->tmp) {
            struct FRAME *tmp = frame->tmp;
            while (tmp) {
                rb_gc_mark_frame(tmp);
                tmp = tmp->prev;
            }
        }
    }
    gc_mark((VALUE)ruby_scope, 0);
    gc_mark((VALUE)ruby_dyna_vars, 0);
    if (finalizer_table) {
        mark_tbl(finalizer_table, 0);
    }

    FLUSH_REGISTER_WINDOWS;
    /* This assumes that all registers are saved into the jmp_buf (and stack) */
    setjmp(save_regs_gc_mark);
    mark_locations_array((VALUE*)save_regs_gc_mark, sizeof(save_regs_gc_mark) / sizeof(VALUE *));
#if STACK_GROW_DIRECTION < 0
    rb_gc_mark_locations((VALUE*)STACK_END, rb_gc_stack_start);
#elif STACK_GROW_DIRECTION > 0
    rb_gc_mark_locations(rb_gc_stack_start, (VALUE*)STACK_END + 1);
#else
    if ((VALUE*)STACK_END < rb_gc_stack_start)
        rb_gc_mark_locations((VALUE*)STACK_END, rb_gc_stack_start);
    else
        rb_gc_mark_locations(rb_gc_stack_start, (VALUE*)STACK_END + 1);
#endif
#ifdef __ia64__
    /* mark backing store (flushed register window on the stack) */
    /* the basic idea from guile GC code                         */
    {
        ucontext_t ctx;
        VALUE *top, *bot;
        getcontext(&ctx);
        mark_locations_array((VALUE*)&ctx.uc_mcontext,
                             ((size_t)(sizeof(VALUE)-1 + sizeof ctx.uc_mcontext)/sizeof(VALUE)));
        bot = (VALUE*)__libc_ia64_register_backing_store_base;
#if defined(__FreeBSD__)
        top = (VALUE*)ctx.uc_mcontext.mc_special.bspstore;
#else
        top = (VALUE*)ctx.uc_mcontext.sc_ar_bsp;
#endif
        rb_gc_mark_locations(bot, top);
    }
#endif
#if defined(__human68k__) || defined(__mc68000__)
    rb_gc_mark_locations((VALUE*)((char*)STACK_END + 2),
                         (VALUE*)((char*)rb_gc_stack_start + 2));
#endif
    rb_gc_mark_threads();

    /* 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();

    rb_mark_tbl(rb_class_tbl);
    rb_gc_mark_trap_list();

    /* 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();
        }
        else {
            gc_mark_rest();
        }
    }
    gc_sweep();
}

void
rb_gc()
{
    garbage_collect();
    rb_gc_finalize_deferred();
}

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

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

void
ruby_set_stack_size(size)
    size_t size;
{
#ifndef STACK_LEVEL_MAX
    STACK_LEVEL_MAX = size / sizeof(VALUE);
#endif
}

void
Init_stack(addr)
    VALUE *addr;
{
#if defined(_WIN32) || defined(__CYGWIN__)
    MEMORY_BASIC_INFORMATION m;
    memset(&m, 0, sizeof(m));
    VirtualQuery(&m, &m, sizeof(m));
    rb_gc_stack_start =
        STACK_UPPER((VALUE *)&m, (VALUE *)m.BaseAddress,
                    (VALUE *)((char *)m.BaseAddress + m.RegionSize) - 1);
#elif defined(STACK_END_ADDRESS)
    extern void *STACK_END_ADDRESS;
    rb_gc_stack_start = STACK_END_ADDRESS;
#else
    if (!addr) addr = (VALUE *)&addr;
    STACK_UPPER(&addr, addr, ++addr);
    if (rb_gc_stack_start) {
        if (STACK_UPPER(&addr,
                        rb_gc_stack_start > addr,
                        rb_gc_stack_start < addr))
            rb_gc_stack_start = addr;
        return;
    }
    rb_gc_stack_start = addr;
#endif
#ifdef HAVE_GETRLIMIT
    {
        struct rlimit rlim;

        if (getrlimit(RLIMIT_STACK, &rlim) == 0) {
            unsigned int space = rlim.rlim_cur/5;

            if (space > 1024*1024) space = 1024*1024;
            STACK_LEVEL_MAX = (rlim.rlim_cur - space) / sizeof(VALUE);
        }
    }
#endif
}


/*
 * 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}" })
 *