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diff --git a/jni/ruby/gc.c b/jni/ruby/gc.c
new file mode 100644
index 0000000..90c4c15
--- /dev/null
+++ b/jni/ruby/gc.c
@@ -0,0 +1,8928 @@
+/**********************************************************************
+
+  gc.c -
+
+  $Author: nagachika $
+  created at: Tue Oct  5 09:44:46 JST 1993
+
+  Copyright (C) 1993-2007 Yukihiro Matsumoto
+  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
+  Copyright (C) 2000  Information-technology Promotion Agency, Japan
+
+**********************************************************************/
+
+#include "internal.h"
+#include "ruby/st.h"
+#include "ruby/re.h"
+#include "ruby/io.h"
+#include "ruby/thread.h"
+#include "ruby/util.h"
+#include "ruby/debug.h"
+#include "eval_intern.h"
+#include "vm_core.h"
+#include "gc.h"
+#include "constant.h"
+#include "ruby_atomic.h"
+#include "probes.h"
+#include <stdio.h>
+#include <stdarg.h>
+#include <setjmp.h>
+#include <sys/types.h>
+#include <assert.h>
+
+#undef rb_data_object_alloc
+
+#ifndef __has_feature
+# define __has_feature(x) 0
+#endif
+
+#ifndef HAVE_MALLOC_USABLE_SIZE
+# ifdef _WIN32
+#   define HAVE_MALLOC_USABLE_SIZE
+#   define malloc_usable_size(a) _msize(a)
+# elif defined HAVE_MALLOC_SIZE
+#   define HAVE_MALLOC_USABLE_SIZE
+#   define malloc_usable_size(a) malloc_size(a)
+# endif
+#endif
+#ifdef HAVE_MALLOC_USABLE_SIZE
+# ifdef HAVE_MALLOC_H
+#  include <malloc.h>
+# elif defined(HAVE_MALLOC_NP_H)
+#  include <malloc_np.h>
+# elif defined(HAVE_MALLOC_MALLOC_H)
+#  include <malloc/malloc.h>
+# endif
+#endif
+
+#if /* is ASAN enabled? */ \
+    __has_feature(address_sanitizer) /* Clang */ || \
+    defined(__SANITIZE_ADDRESS__)  /* GCC 4.8.x */
+  #define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS \
+        __attribute__((no_address_safety_analysis)) \
+        __attribute__((noinline))
+#else
+  #define ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS
+#endif
+
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+
+#ifdef HAVE_SYS_RESOURCE_H
+#include <sys/resource.h>
+#endif
+#if defined(__native_client__) && defined(NACL_NEWLIB)
+# include "nacl/resource.h"
+# undef HAVE_POSIX_MEMALIGN
+# undef HAVE_MEMALIGN
+
+#endif
+
+#if defined _WIN32 || defined __CYGWIN__
+#include <windows.h>
+#elif defined(HAVE_POSIX_MEMALIGN)
+#elif defined(HAVE_MEMALIGN)
+#include <malloc.h>
+#endif
+
+#define rb_setjmp(env) RUBY_SETJMP(env)
+#define rb_jmp_buf rb_jmpbuf_t
+
+#if defined(HAVE_RB_GC_GUARDED_PTR_VAL) && HAVE_RB_GC_GUARDED_PTR_VAL
+/* trick the compiler into thinking a external signal handler uses this */
+volatile VALUE rb_gc_guarded_val;
+volatile VALUE *
+rb_gc_guarded_ptr_val(volatile VALUE *ptr, VALUE val)
+{
+    rb_gc_guarded_val = val;
+
+    return ptr;
+}
+#endif
+
+#ifndef GC_HEAP_INIT_SLOTS
+#define GC_HEAP_INIT_SLOTS 10000
+#endif
+#ifndef GC_HEAP_FREE_SLOTS
+#define GC_HEAP_FREE_SLOTS  4096
+#endif
+#ifndef GC_HEAP_GROWTH_FACTOR
+#define GC_HEAP_GROWTH_FACTOR 1.8
+#endif
+#ifndef GC_HEAP_GROWTH_MAX_SLOTS
+#define GC_HEAP_GROWTH_MAX_SLOTS 0 /* 0 is disable */
+#endif
+#ifndef GC_HEAP_OLDOBJECT_LIMIT_FACTOR
+#define GC_HEAP_OLDOBJECT_LIMIT_FACTOR 2.0
+#endif
+
+#ifndef GC_HEAP_FREE_SLOTS_MIN_RATIO
+#define GC_HEAP_FREE_SLOTS_MIN_RATIO 0.3
+#endif
+#ifndef GC_HEAP_FREE_SLOTS_MAX_RATIO
+#define GC_HEAP_FREE_SLOTS_MAX_RATIO 0.8
+#endif
+
+#ifndef GC_MALLOC_LIMIT_MIN
+#define GC_MALLOC_LIMIT_MIN (16 * 1024 * 1024 /* 16MB */)
+#endif
+#ifndef GC_MALLOC_LIMIT_MAX
+#define GC_MALLOC_LIMIT_MAX (32 * 1024 * 1024 /* 32MB */)
+#endif
+#ifndef GC_MALLOC_LIMIT_GROWTH_FACTOR
+#define GC_MALLOC_LIMIT_GROWTH_FACTOR 1.4
+#endif
+
+#ifndef GC_OLDMALLOC_LIMIT_MIN
+#define GC_OLDMALLOC_LIMIT_MIN (16 * 1024 * 1024 /* 16MB */)
+#endif
+#ifndef GC_OLDMALLOC_LIMIT_GROWTH_FACTOR
+#define GC_OLDMALLOC_LIMIT_GROWTH_FACTOR 1.2
+#endif
+#ifndef GC_OLDMALLOC_LIMIT_MAX
+#define GC_OLDMALLOC_LIMIT_MAX (128 * 1024 * 1024 /* 128MB */)
+#endif
+
+#ifndef PRINT_MEASURE_LINE
+#define PRINT_MEASURE_LINE 0
+#endif
+#ifndef PRINT_ENTER_EXIT_TICK
+#define PRINT_ENTER_EXIT_TICK 0
+#endif
+#ifndef PRINT_ROOT_TICKS
+#define PRINT_ROOT_TICKS 0
+#endif
+
+#define USE_TICK_T                 (PRINT_ENTER_EXIT_TICK || PRINT_MEASURE_LINE)
+#define TICK_TYPE 1
+
+typedef struct {
+    size_t heap_init_slots;
+    size_t heap_free_slots;
+    double growth_factor;
+    size_t growth_max_slots;
+    double oldobject_limit_factor;
+    size_t malloc_limit_min;
+    size_t malloc_limit_max;
+    double malloc_limit_growth_factor;
+    size_t oldmalloc_limit_min;
+    size_t oldmalloc_limit_max;
+    double oldmalloc_limit_growth_factor;
+    VALUE gc_stress;
+} ruby_gc_params_t;
+
+static ruby_gc_params_t gc_params = {
+    GC_HEAP_INIT_SLOTS,
+    GC_HEAP_FREE_SLOTS,
+    GC_HEAP_GROWTH_FACTOR,
+    GC_HEAP_GROWTH_MAX_SLOTS,
+    GC_HEAP_OLDOBJECT_LIMIT_FACTOR,
+    GC_MALLOC_LIMIT_MIN,
+    GC_MALLOC_LIMIT_MAX,
+    GC_MALLOC_LIMIT_GROWTH_FACTOR,
+    GC_OLDMALLOC_LIMIT_MIN,
+    GC_OLDMALLOC_LIMIT_MAX,
+    GC_OLDMALLOC_LIMIT_GROWTH_FACTOR,
+#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
+    FALSE,
+#endif
+};
+
+/* GC_DEBUG:
+ *  enable to embed GC debugging information.
+ */
+#ifndef GC_DEBUG
+#define GC_DEBUG 0
+#endif
+
+#if USE_RGENGC
+/* RGENGC_DEBUG:
+ * 1: basic information
+ * 2: remember set operation
+ * 3: mark
+ * 4:
+ * 5: sweep
+ */
+#ifndef RGENGC_DEBUG
+#define RGENGC_DEBUG       0
+#endif
+
+/* RGENGC_CHECK_MODE
+ * 0: disable all assertions
+ * 1: enable assertions (to debug RGenGC)
+ * 2: enable internal consistency check at each GC (for debugging)
+ * 3: enable internal consistency check at each GC steps (for debugging)
+ * 4: enable livness check
+ * 5: show all references
+ */
+#ifndef RGENGC_CHECK_MODE
+#define RGENGC_CHECK_MODE  0
+#endif
+
+/* RGENGC_PROFILE
+ * 0: disable RGenGC profiling
+ * 1: enable profiling for basic information
+ * 2: enable profiling for each types
+ */
+#ifndef RGENGC_PROFILE
+#define RGENGC_PROFILE     0
+#endif
+
+/* RGENGC_ESTIMATE_OLDMALLOC
+ * Enable/disable to estimate increase size of malloc'ed size by old objects.
+ * If estimation exceeds threshold, then will invoke full GC.
+ * 0: disable estimation.
+ * 1: enable estimation.
+ */
+#ifndef RGENGC_ESTIMATE_OLDMALLOC
+#define RGENGC_ESTIMATE_OLDMALLOC 1
+#endif
+
+/* RGENGC_FORCE_MAJOR_GC
+ * Force major/full GC if this macro is not 0.
+ */
+#ifndef RGENGC_FORCE_MAJOR_GC
+#define RGENGC_FORCE_MAJOR_GC 0
+#endif
+
+#else /* USE_RGENGC */
+
+#ifdef RGENGC_DEBUG
+#undef RGENGC_DEBUG
+#endif
+#define RGENGC_DEBUG       0
+#ifdef RGENGC_CHECK_MODE
+#undef RGENGC_CHECK_MODE
+#endif
+#define RGENGC_CHECK_MODE  0
+#define RGENGC_PROFILE     0
+#define RGENGC_ESTIMATE_OLDMALLOC 0
+#define RGENGC_FORCE_MAJOR_GC 0
+
+#endif /* USE_RGENGC */
+
+#ifndef GC_PROFILE_MORE_DETAIL
+#define GC_PROFILE_MORE_DETAIL 0
+#endif
+#ifndef GC_PROFILE_DETAIL_MEMORY
+#define GC_PROFILE_DETAIL_MEMORY 0
+#endif
+#ifndef GC_ENABLE_INCREMENTAL_MARK
+#define GC_ENABLE_INCREMENTAL_MARK USE_RINCGC
+#endif
+#ifndef GC_ENABLE_LAZY_SWEEP
+#define GC_ENABLE_LAZY_SWEEP   1
+#endif
+#ifndef CALC_EXACT_MALLOC_SIZE
+#define CALC_EXACT_MALLOC_SIZE 0
+#endif
+#if defined(HAVE_MALLOC_USABLE_SIZE) || CALC_EXACT_MALLOC_SIZE > 0
+#ifndef MALLOC_ALLOCATED_SIZE
+#define MALLOC_ALLOCATED_SIZE 0
+#endif
+#else
+#define MALLOC_ALLOCATED_SIZE 0
+#endif
+#ifndef MALLOC_ALLOCATED_SIZE_CHECK
+#define MALLOC_ALLOCATED_SIZE_CHECK 0
+#endif
+
+typedef enum {
+    GPR_FLAG_NONE               = 0x000,
+    /* major reason */
+    GPR_FLAG_MAJOR_BY_NOFREE    = 0x001,
+    GPR_FLAG_MAJOR_BY_OLDGEN    = 0x002,
+    GPR_FLAG_MAJOR_BY_SHADY     = 0x004,
+    GPR_FLAG_MAJOR_BY_FORCE     = 0x008,
+#if RGENGC_ESTIMATE_OLDMALLOC
+    GPR_FLAG_MAJOR_BY_OLDMALLOC = 0x020,
+#endif
+    GPR_FLAG_MAJOR_MASK         = 0x0ff,
+
+    /* gc reason */
+    GPR_FLAG_NEWOBJ             = 0x100,
+    GPR_FLAG_MALLOC             = 0x200,
+    GPR_FLAG_METHOD             = 0x400,
+    GPR_FLAG_CAPI               = 0x800,
+    GPR_FLAG_STRESS            = 0x1000,
+
+    /* others */
+    GPR_FLAG_IMMEDIATE_SWEEP   = 0x2000,
+    GPR_FLAG_HAVE_FINALIZE     = 0x4000
+} gc_profile_record_flag;
+
+typedef struct gc_profile_record {
+    int flags;
+
+    double gc_time;
+    double gc_invoke_time;
+
+    size_t heap_total_objects;
+    size_t heap_use_size;
+    size_t heap_total_size;
+
+#if GC_PROFILE_MORE_DETAIL
+    double gc_mark_time;
+    double gc_sweep_time;
+
+    size_t heap_use_pages;
+    size_t heap_live_objects;
+    size_t heap_free_objects;
+
+    size_t allocate_increase;
+    size_t allocate_limit;
+
+    double prepare_time;
+    size_t removing_objects;
+    size_t empty_objects;
+#if GC_PROFILE_DETAIL_MEMORY
+    long maxrss;
+    long minflt;
+    long majflt;
+#endif
+#endif
+#if MALLOC_ALLOCATED_SIZE
+    size_t allocated_size;
+#endif
+
+#if RGENGC_PROFILE > 0
+    size_t old_objects;
+    size_t remembered_normal_objects;
+    size_t remembered_shady_objects;
+#endif
+} gc_profile_record;
+
+#if defined(_MSC_VER) || defined(__BORLANDC__) || defined(__CYGWIN__)
+#pragma pack(push, 1) /* magic for reducing sizeof(RVALUE): 24 -> 20 */
+#endif
+
+typedef struct RVALUE {
+    union {
+	struct {
+	    VALUE flags;		/* always 0 for freed obj */
+	    struct RVALUE *next;
+	} free;
+	struct RBasic  basic;
+	struct RObject object;
+	struct RClass  klass;
+	struct RFloat  flonum;
+	struct RString string;
+	struct RArray  array;
+	struct RRegexp regexp;
+	struct RHash   hash;
+	struct RData   data;
+	struct RTypedData   typeddata;
+	struct RStruct rstruct;
+	struct RBignum bignum;
+	struct RFile   file;
+	struct RNode   node;
+	struct RMatch  match;
+	struct RRational rational;
+	struct RComplex complex;
+	struct {
+	    struct RBasic basic;
+	    VALUE v1;
+	    VALUE v2;
+	    VALUE v3;
+	} values;
+    } as;
+#if GC_DEBUG
+    const char *file;
+    int line;
+#endif
+} RVALUE;
+
+#if defined(_MSC_VER) || defined(__BORLANDC__) || defined(__CYGWIN__)
+#pragma pack(pop)
+#endif
+
+typedef uintptr_t bits_t;
+enum {
+    BITS_SIZE = sizeof(bits_t),
+    BITS_BITLENGTH = ( BITS_SIZE * CHAR_BIT )
+};
+
+struct heap_page_header {
+    struct heap_page *page;
+};
+
+struct heap_page_body {
+    struct heap_page_header header;
+    /* char gap[];      */
+    /* RVALUE values[]; */
+};
+
+struct gc_list {
+    VALUE *varptr;
+    struct gc_list *next;
+};
+
+#define STACK_CHUNK_SIZE 500
+
+typedef struct stack_chunk {
+    VALUE data[STACK_CHUNK_SIZE];
+    struct stack_chunk *next;
+} stack_chunk_t;
+
+typedef struct mark_stack {
+    stack_chunk_t *chunk;
+    stack_chunk_t *cache;
+    int index;
+    int limit;
+    size_t cache_size;
+    size_t unused_cache_size;
+} mark_stack_t;
+
+typedef struct rb_heap_struct {
+    RVALUE *freelist;
+
+    struct heap_page *free_pages;
+    struct heap_page *using_page;
+    struct heap_page *pages;
+    struct heap_page *sweep_pages;
+#if GC_ENABLE_INCREMENTAL_MARK
+    struct heap_page *pooled_pages;
+#endif
+    size_t page_length;      /* total page count in a heap */
+    size_t total_slots;      /* total slot count (page_length * HEAP_OBJ_LIMIT) */
+} rb_heap_t;
+
+enum gc_stat {
+    gc_stat_none,
+    gc_stat_marking,
+    gc_stat_sweeping
+};
+
+typedef struct rb_objspace {
+    struct {
+	size_t limit;
+	size_t increase;
+#if MALLOC_ALLOCATED_SIZE
+	size_t allocated_size;
+	size_t allocations;
+#endif
+    } malloc_params;
+
+    struct {
+	enum gc_stat stat : 2;
+	unsigned int immediate_sweep : 1;
+	unsigned int dont_gc : 1;
+	unsigned int dont_incremental : 1;
+	unsigned int during_gc : 1;
+	unsigned int gc_stressful: 1;
+#if USE_RGENGC
+	unsigned int during_minor_gc : 1;
+#endif
+#if GC_ENABLE_INCREMENTAL_MARK
+	unsigned int during_incremental_marking : 1;
+#endif
+    } flags;
+
+    rb_event_flag_t hook_events;
+    size_t total_allocated_objects;
+
+    rb_heap_t eden_heap;
+    rb_heap_t tomb_heap; /* heap for zombies and ghosts */
+
+    struct {
+	rb_atomic_t finalizing;
+    } atomic_flags;
+
+    struct mark_func_data_struct {
+	void *data;
+	void (*mark_func)(VALUE v, void *data);
+    } *mark_func_data;
+
+    mark_stack_t mark_stack;
+    size_t marked_slots;
+
+    struct {
+	struct heap_page **sorted;
+	size_t allocated_pages;
+	size_t allocatable_pages;
+	size_t sorted_length;
+	RVALUE *range[2];
+
+	size_t swept_slots;
+	size_t min_free_slots;
+	size_t max_free_slots;
+
+	/* final */
+	size_t final_slots;
+	VALUE deferred_final;
+    } heap_pages;
+
+    st_table *finalizer_table;
+
+    struct {
+	int run;
+	int latest_gc_info;
+	gc_profile_record *records;
+	gc_profile_record *current_record;
+	size_t next_index;
+	size_t size;
+
+#if GC_PROFILE_MORE_DETAIL
+	double prepare_time;
+#endif
+	double invoke_time;
+
+#if USE_RGENGC
+	size_t minor_gc_count;
+	size_t major_gc_count;
+#if RGENGC_PROFILE > 0
+	size_t total_generated_normal_object_count;
+	size_t total_generated_shady_object_count;
+	size_t total_shade_operation_count;
+	size_t total_promoted_count;
+	size_t total_remembered_normal_object_count;
+	size_t total_remembered_shady_object_count;
+
+#if RGENGC_PROFILE >= 2
+	size_t generated_normal_object_count_types[RUBY_T_MASK];
+	size_t generated_shady_object_count_types[RUBY_T_MASK];
+	size_t shade_operation_count_types[RUBY_T_MASK];
+	size_t promoted_types[RUBY_T_MASK];
+	size_t remembered_normal_object_count_types[RUBY_T_MASK];
+	size_t remembered_shady_object_count_types[RUBY_T_MASK];
+#endif
+#endif /* RGENGC_PROFILE */
+#endif /* USE_RGENGC */
+
+	/* temporary profiling space */
+	double gc_sweep_start_time;
+	size_t total_allocated_objects_at_gc_start;
+	size_t heap_used_at_gc_start;
+
+	/* basic statistics */
+	size_t count;
+	size_t total_freed_objects;
+	size_t total_allocated_pages;
+	size_t total_freed_pages;
+    } profile;
+    struct gc_list *global_list;
+
+    VALUE gc_stress_mode;
+
+#if USE_RGENGC
+    struct {
+	VALUE parent_object;
+	int need_major_gc;
+	size_t last_major_gc;
+	size_t remembered_wb_unprotected_objects;
+	size_t remembered_wb_unprotected_objects_limit;
+	size_t old_objects;
+	size_t old_objects_limit;
+
+#if RGENGC_ESTIMATE_OLDMALLOC
+	size_t oldmalloc_increase;
+	size_t oldmalloc_increase_limit;
+#endif
+
+#if RGENGC_CHECK_MODE >= 2
+	struct st_table *allrefs_table;
+	size_t error_count;
+#endif
+    } rgengc;
+#if GC_ENABLE_INCREMENTAL_MARK
+    struct {
+	size_t pooled_slots;
+	size_t step_slots;
+    } rincgc;
+#endif
+#endif /* USE_RGENGC */
+} rb_objspace_t;
+
+
+#ifndef HEAP_ALIGN_LOG
+/* default tiny heap size: 16KB */
+#define HEAP_ALIGN_LOG 14
+#endif
+#define CEILDIV(i, mod) (((i) + (mod) - 1)/(mod))
+enum {
+    HEAP_ALIGN = (1UL << HEAP_ALIGN_LOG),
+    HEAP_ALIGN_MASK = (~(~0UL << HEAP_ALIGN_LOG)),
+    REQUIRED_SIZE_BY_MALLOC = (sizeof(size_t) * 5),
+    HEAP_SIZE = (HEAP_ALIGN - REQUIRED_SIZE_BY_MALLOC),
+    HEAP_OBJ_LIMIT = (unsigned int)((HEAP_SIZE - sizeof(struct heap_page_header))/sizeof(struct RVALUE)),
+    HEAP_BITMAP_LIMIT = CEILDIV(CEILDIV(HEAP_SIZE, sizeof(struct RVALUE)), BITS_BITLENGTH),
+    HEAP_BITMAP_SIZE = ( BITS_SIZE * HEAP_BITMAP_LIMIT),
+    HEAP_BITMAP_PLANES = USE_RGENGC ? 3 : 1 /* RGENGC: mark bits, rememberset bits and oldgen bits */
+};
+
+struct heap_page {
+    struct heap_page_body *body;
+    struct heap_page *prev;
+    rb_heap_t *heap;
+    int total_slots;
+    int free_slots;
+    int final_slots;
+    struct {
+	unsigned int before_sweep : 1;
+	unsigned int has_remembered_objects : 1;
+	unsigned int has_long_lived_shady_objects : 1;
+    } flags;
+
+    struct heap_page *free_next;
+    RVALUE *start;
+    RVALUE *freelist;
+    struct heap_page *next;
+
+#if USE_RGENGC
+    bits_t wb_unprotected_bits[HEAP_BITMAP_LIMIT];
+#endif
+    /* the following three bitmaps are cleared at the beggining of full GC */
+    bits_t mark_bits[HEAP_BITMAP_LIMIT];
+#if USE_RGENGC
+    bits_t long_lived_bits[HEAP_BITMAP_LIMIT];
+    bits_t marking_bits[HEAP_BITMAP_LIMIT];
+#endif
+};
+
+#define GET_PAGE_BODY(x)   ((struct heap_page_body *)((bits_t)(x) & ~(HEAP_ALIGN_MASK)))
+#define GET_PAGE_HEADER(x) (&GET_PAGE_BODY(x)->header)
+#define GET_HEAP_PAGE(x)   (GET_PAGE_HEADER(x)->page)
+
+#define NUM_IN_PAGE(p)   (((bits_t)(p) & HEAP_ALIGN_MASK)/sizeof(RVALUE))
+#define BITMAP_INDEX(p)  (NUM_IN_PAGE(p) / BITS_BITLENGTH )
+#define BITMAP_OFFSET(p) (NUM_IN_PAGE(p) & (BITS_BITLENGTH-1))
+#define BITMAP_BIT(p)    ((bits_t)1 << BITMAP_OFFSET(p))
+
+/* Bitmap Operations */
+#define MARKED_IN_BITMAP(bits, p)    ((bits)[BITMAP_INDEX(p)] & BITMAP_BIT(p))
+#define MARK_IN_BITMAP(bits, p)      ((bits)[BITMAP_INDEX(p)] = (bits)[BITMAP_INDEX(p)] | BITMAP_BIT(p))
+#define CLEAR_IN_BITMAP(bits, p)     ((bits)[BITMAP_INDEX(p)] = (bits)[BITMAP_INDEX(p)] & ~BITMAP_BIT(p))
+
+/* getting bitmap */
+#define GET_HEAP_MARK_BITS(x)           (&GET_HEAP_PAGE(x)->mark_bits[0])
+#if USE_RGENGC
+#define GET_HEAP_LONG_LIVED_BITS(x)     (&GET_HEAP_PAGE(x)->long_lived_bits[0])
+#define GET_HEAP_WB_UNPROTECTED_BITS(x) (&GET_HEAP_PAGE(x)->wb_unprotected_bits[0])
+#define GET_HEAP_MARKING_BITS(x)        (&GET_HEAP_PAGE(x)->marking_bits[0])
+#endif
+
+/* Aliases */
+#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
+#define rb_objspace (*GET_VM()->objspace)
+#else
+static rb_objspace_t rb_objspace = {{GC_MALLOC_LIMIT_MIN}};
+#endif
+
+#define ruby_initial_gc_stress	gc_params.gc_stress
+VALUE *ruby_initial_gc_stress_ptr = &ruby_initial_gc_stress;
+
+#define malloc_limit		objspace->malloc_params.limit
+#define malloc_increase 	objspace->malloc_params.increase
+#define malloc_allocated_size 	objspace->malloc_params.allocated_size
+#define heap_pages_sorted       objspace->heap_pages.sorted
+#define heap_allocated_pages    objspace->heap_pages.allocated_pages
+#define heap_pages_sorted_length objspace->heap_pages.sorted_length
+#define heap_pages_lomem	objspace->heap_pages.range[0]
+#define heap_pages_himem	objspace->heap_pages.range[1]
+#define heap_pages_swept_slots	objspace->heap_pages.swept_slots
+#define heap_allocatable_pages	objspace->heap_pages.allocatable_pages
+#define heap_pages_min_free_slots	objspace->heap_pages.min_free_slots
+#define heap_pages_max_free_slots	objspace->heap_pages.max_free_slots
+#define heap_pages_final_slots		objspace->heap_pages.final_slots
+#define heap_pages_deferred_final	objspace->heap_pages.deferred_final
+#define heap_eden               (&objspace->eden_heap)
+#define heap_tomb               (&objspace->tomb_heap)
+#define dont_gc 		objspace->flags.dont_gc
+#define during_gc		objspace->flags.during_gc
+#define finalizing		objspace->atomic_flags.finalizing
+#define finalizer_table 	objspace->finalizer_table
+#define global_list		objspace->global_list
+#define ruby_gc_stressful	objspace->flags.gc_stressful
+#define ruby_gc_stress_mode     objspace->gc_stress_mode
+
+#define is_marking(objspace)             ((objspace)->flags.stat == gc_stat_marking)
+#define is_sweeping(objspace)            ((objspace)->flags.stat == gc_stat_sweeping)
+#if USE_RGENGC
+#define is_full_marking(objspace)        ((objspace)->flags.during_minor_gc == FALSE)
+#else
+#define is_full_marking(objspace)        TRUE
+#endif
+#if GC_ENABLE_INCREMENTAL_MARK
+#define is_incremental_marking(objspace) ((objspace)->flags.during_incremental_marking != FALSE)
+#else
+#define is_incremental_marking(objspace) FALSE
+#endif
+#if GC_ENABLE_INCREMENTAL_MARK
+#define will_be_incremental_marking(objspace) ((objspace)->rgengc.need_major_gc != GPR_FLAG_NONE)
+#else
+#define will_be_incremental_marking(objspace) FALSE
+#endif
+#define has_sweeping_pages(heap)         ((heap)->sweep_pages != 0)
+#define is_lazy_sweeping(heap)           (GC_ENABLE_LAZY_SWEEP && has_sweeping_pages(heap))
+
+#if SIZEOF_LONG == SIZEOF_VOIDP
+# define nonspecial_obj_id(obj) (VALUE)((SIGNED_VALUE)(obj)|FIXNUM_FLAG)
+# define obj_id_to_ref(objid) ((objid) ^ FIXNUM_FLAG) /* unset FIXNUM_FLAG */
+#elif SIZEOF_LONG_LONG == SIZEOF_VOIDP
+# define nonspecial_obj_id(obj) LL2NUM((SIGNED_VALUE)(obj) / 2)
+# define obj_id_to_ref(objid) (FIXNUM_P(objid) ? \
+   ((objid) ^ FIXNUM_FLAG) : (NUM2PTR(objid) << 1))
+#else
+# error not supported
+#endif
+
+#define RANY(o) ((RVALUE*)(o))
+
+struct RZombie {
+    struct RBasic basic;
+    VALUE next;
+    void (*dfree)(void *);
+    void *data;
+};
+
+#define RZOMBIE(o) ((struct RZombie *)(o))
+
+#define nomem_error GET_VM()->special_exceptions[ruby_error_nomemory]
+
+int ruby_gc_debug_indent = 0;
+VALUE rb_mGC;
+int ruby_disable_gc = 0;
+
+void rb_gcdebug_print_obj_condition(VALUE obj);
+
+static void rb_objspace_call_finalizer(rb_objspace_t *objspace);
+static VALUE define_final0(VALUE obj, VALUE block);
+
+static void negative_size_allocation_error(const char *);
+static void *aligned_malloc(size_t, size_t);
+static void aligned_free(void *);
+
+static void init_mark_stack(mark_stack_t *stack);
+
+static int ready_to_gc(rb_objspace_t *objspace);
+
+static int garbage_collect(rb_objspace_t *, int full_mark, int immediate_mark, int immediate_sweep, int reason);
+
+static int  gc_start(rb_objspace_t *objspace, const int full_mark, const int immediate_mark, const unsigned int immediate_sweep, int reason);
+static void gc_rest(rb_objspace_t *objspace);
+static inline void gc_enter(rb_objspace_t *objspace, const char *event);
+static inline void gc_exit(rb_objspace_t *objspace, const char *event);
+
+static void gc_marks(rb_objspace_t *objspace, int full_mark);
+static void gc_marks_start(rb_objspace_t *objspace, int full);
+static int  gc_marks_finish(rb_objspace_t *objspace);
+static void gc_marks_rest(rb_objspace_t *objspace);
+#if GC_ENABLE_INCREMENTAL_MARK
+static void gc_marks_step(rb_objspace_t *objspace, int slots);
+static void gc_marks_continue(rb_objspace_t *objspace, rb_heap_t *heap);
+#endif
+
+static void gc_sweep(rb_objspace_t *objspace);
+static void gc_sweep_start(rb_objspace_t *objspace);
+static void gc_sweep_finish(rb_objspace_t *objspace);
+static int  gc_sweep_step(rb_objspace_t *objspace, rb_heap_t *heap);
+static void gc_sweep_rest(rb_objspace_t *objspace);
+#if GC_ENABLE_LAZY_SWEEP
+static void gc_sweep_continue(rb_objspace_t *objspace, rb_heap_t *heap);
+#endif
+
+static void gc_mark(rb_objspace_t *objspace, VALUE ptr);
+static void gc_mark_ptr(rb_objspace_t *objspace, VALUE ptr);
+static void gc_mark_maybe(rb_objspace_t *objspace, VALUE ptr);
+static void gc_mark_children(rb_objspace_t *objspace, VALUE ptr);
+
+static int gc_mark_stacked_objects_incremental(rb_objspace_t *, size_t count);
+static int gc_mark_stacked_objects_all(rb_objspace_t *);
+static void gc_grey(rb_objspace_t *objspace, VALUE ptr);
+
+static inline int is_pointer_to_heap(rb_objspace_t *objspace, void *ptr);
+
+static void   push_mark_stack(mark_stack_t *, VALUE);
+static int    pop_mark_stack(mark_stack_t *, VALUE *);
+static size_t mark_stack_size(mark_stack_t *stack);
+static void   shrink_stack_chunk_cache(mark_stack_t *stack);
+
+static size_t obj_memsize_of(VALUE obj, int use_all_types);
+static VALUE gc_verify_internal_consistency(VALUE self);
+static int gc_verify_heap_page(rb_objspace_t *objspace, struct heap_page *page, VALUE obj);
+static int gc_verify_heap_pages(rb_objspace_t *objspace);
+
+static void gc_stress_set(rb_objspace_t *objspace, VALUE flag);
+
+static double getrusage_time(void);
+static inline void gc_prof_setup_new_record(rb_objspace_t *objspace, int reason);
+static inline void gc_prof_timer_start(rb_objspace_t *);
+static inline void gc_prof_timer_stop(rb_objspace_t *);
+static inline void gc_prof_mark_timer_start(rb_objspace_t *);
+static inline void gc_prof_mark_timer_stop(rb_objspace_t *);
+static inline void gc_prof_sweep_timer_start(rb_objspace_t *);
+static inline void gc_prof_sweep_timer_stop(rb_objspace_t *);
+static inline void gc_prof_set_malloc_info(rb_objspace_t *);
+static inline void gc_prof_set_heap_info(rb_objspace_t *);
+
+#define gc_prof_record(objspace) (objspace)->profile.current_record
+#define gc_prof_enabled(objspace) ((objspace)->profile.run && (objspace)->profile.current_record)
+
+#ifdef HAVE_VA_ARGS_MACRO
+# define gc_report(level, objspace, fmt, ...) \
+    if ((level) > RGENGC_DEBUG) {} else gc_report_body(level, objspace, fmt, ##__VA_ARGS__)
+#else
+# define gc_report if (!(RGENGC_DEBUG)) {} else gc_report_body
+#endif
+PRINTF_ARGS(static void gc_report_body(int level, rb_objspace_t *objspace, const char *fmt, ...), 3, 4);
+static const char *obj_info(VALUE obj);
+
+#define PUSH_MARK_FUNC_DATA(v) do { \
+    struct mark_func_data_struct *prev_mark_func_data = objspace->mark_func_data; \
+    objspace->mark_func_data = (v);
+
+#define POP_MARK_FUNC_DATA() objspace->mark_func_data = prev_mark_func_data;} while (0)
+
+/*
+ * 1 - TSC (H/W Time Stamp Counter)
+ * 2 - getrusage
+ */
+#ifndef TICK_TYPE
+#define TICK_TYPE 1
+#endif
+
+#if USE_TICK_T
+
+#if TICK_TYPE == 1
+/* the following code is only for internal tuning. */
+
+/* Source code to use RDTSC is quoted and modified from
+ * http://www.mcs.anl.gov/~kazutomo/rdtsc.html
+ * written by Kazutomo Yoshii <kazutomo@mcs.anl.gov>
+ */
+
+#if defined(__GNUC__) && defined(__i386__)
+typedef unsigned long long tick_t;
+#define PRItick "llu"
+static inline tick_t
+tick(void)
+{
+    unsigned long long int x;
+    __asm__ __volatile__ ("rdtsc" : "=A" (x));
+    return x;
+}
+
+#elif defined(__GNUC__) && defined(__x86_64__)
+typedef unsigned long long tick_t;
+#define PRItick "llu"
+
+static __inline__ tick_t
+tick(void)
+{
+    unsigned long hi, lo;
+    __asm__ __volatile__ ("rdtsc" : "=a"(lo), "=d"(hi));
+    return ((unsigned long long)lo)|( ((unsigned long long)hi)<<32);
+}
+
+#elif defined(_WIN32) && defined(_MSC_VER)
+#include <intrin.h>
+typedef unsigned __int64 tick_t;
+#define PRItick "llu"
+
+static inline tick_t
+tick(void)
+{
+    return __rdtsc();
+}
+
+#else /* use clock */
+typedef clock_t tick_t;
+#define PRItick "llu"
+
+static inline tick_t
+tick(void)
+{
+    return clock();
+}
+#endif /* TSC */
+
+#elif TICK_TYPE == 2
+typedef double tick_t;
+#define PRItick "4.9f"
+
+static inline tick_t
+tick(void)
+{
+    return getrusage_time();
+}
+#else /* TICK_TYPE */
+#error "choose tick type"
+#endif /* TICK_TYPE */
+
+#define MEASURE_LINE(expr) do { \
+    volatile tick_t start_time = tick(); \
+    volatile tick_t end_time; \
+    expr; \
+    end_time = tick(); \
+    fprintf(stderr, "0\t%"PRItick"\t%s\n", end_time - start_time, #expr); \
+} while (0)
+
+#else /* USE_TICK_T */
+#define MEASURE_LINE(expr) expr
+#endif /* USE_TICK_T */
+
+#define FL_TEST2(x,f)         ((RGENGC_CHECK_MODE && SPECIAL_CONST_P(x)) ? (rb_bug("FL_TEST2: SPECIAL_CONST (%p)", (void *)(x)), 0) : FL_TEST_RAW((x),(f)) != 0)
+#define FL_SET2(x,f)          do {if (RGENGC_CHECK_MODE && SPECIAL_CONST_P(x)) rb_bug("FL_SET2: SPECIAL_CONST");   RBASIC(x)->flags |= (f);} while (0)
+#define FL_UNSET2(x,f)        do {if (RGENGC_CHECK_MODE && SPECIAL_CONST_P(x)) rb_bug("FL_UNSET2: SPECIAL_CONST"); RBASIC(x)->flags &= ~(f);} while (0)
+
+#define RVALUE_MARK_BITMAP(obj)           MARKED_IN_BITMAP(GET_HEAP_MARK_BITS(obj), (obj))
+#define RVALUE_PAGE_MARKED(page, obj)     MARKED_IN_BITMAP((page)->mark_bits, (obj))
+
+#if USE_RGENGC
+#define RVALUE_WB_UNPROTECTED_BITMAP(obj) MARKED_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(obj), (obj))
+#define RVALUE_LONG_LIVED_BITMAP(obj)     MARKED_IN_BITMAP(GET_HEAP_LONG_LIVED_BITS(obj), (obj))
+#define RVALUE_MARKING_BITMAP(obj)        MARKED_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), (obj))
+
+#define RVALUE_PAGE_WB_UNPROTECTED(apge, obj) MARKED_IN_BITMAP((page)->wb_unprotected_bits, (obj))
+#define RVALUE_PAGE_LONG_LIVED(page, obj)     MARKED_IN_BITMAP((page)->long_lived_bits, (obj))
+#define RVALUE_PAGE_MARKING(page, obj)        MARKED_IN_BITMAP((page)->marking_bits, (obj))
+
+#define RVALUE_OLD_AGE   3
+#define RVALUE_AGE_SHIFT 5 /* FL_PROMOTED0 bit */
+
+static int rgengc_remembered(rb_objspace_t *objspace, VALUE obj);
+static int rgengc_remember(rb_objspace_t *objspace, VALUE obj);
+static void rgengc_mark_and_rememberset_clear(rb_objspace_t *objspace, rb_heap_t *heap);
+static void rgengc_rememberset_mark(rb_objspace_t *objspace, rb_heap_t *heap);
+
+static inline int
+RVALUE_FLAGS_AGE(VALUE flags)
+{
+    return (int)((flags & (FL_PROMOTED0 | FL_PROMOTED1)) >> RVALUE_AGE_SHIFT);
+}
+
+#endif /* USE_RGENGC */
+
+static inline VALUE
+check_rvalue_consistency(const VALUE obj)
+{
+#if RGENGC_CHECK_MODE > 0
+    rb_objspace_t *objspace = &rb_objspace;
+
+    if (!is_pointer_to_heap(objspace, (void *)obj)) {
+	rb_bug("check_rvalue_consistency: %p is not a Ruby object.", (void *)obj);
+    }
+    else if (SPECIAL_CONST_P(obj)) {
+	rb_bug("check_rvalue_consistency: %p is a special const.", (void *)obj);
+    }
+    else {
+	int wb_unprotected_bit = RVALUE_WB_UNPROTECTED_BITMAP(obj) != 0;
+	int long_lived_bit = RVALUE_LONG_LIVED_BITMAP(obj) != 0;
+	int age = RVALUE_FLAGS_AGE(RBASIC(obj)->flags);
+
+	if (BUILTIN_TYPE(obj) == T_NONE)   rb_bug("check_rvalue_consistency: %p is T_NONE", obj_info(obj));
+	if (BUILTIN_TYPE(obj) == T_ZOMBIE) rb_bug("check_rvalue_consistency: %p is T_ZOMBIE", obj_info(obj));
+	obj_memsize_of((VALUE)obj, FALSE);
+
+	/* check generation
+	 *
+	 * OLD == age == 3 && old-bitmap && mark-bit (except incremental marking)
+	 */
+	if (age > 0 && wb_unprotected_bit) {
+	    rb_bug("check_rvalue_consistency: %s is not WB protected, but age is %d > 0.", obj_info(obj), age);
+	}
+	if (!is_full_marking(objspace) && long_lived_bit && age != RVALUE_OLD_AGE && !wb_unprotected_bit) {
+	    rb_bug("check_rvalue_consistency: %s is long lived, but not old (age: %d) and not WB unprotected.\n", obj_info(obj), age);
+	}
+	if (!is_marking(objspace) && !is_sweeping(objspace) && long_lived_bit && RVALUE_MARK_BITMAP(obj) == 0) {
+	    rb_bug("check_rvalue_consistency: %s is long lived, but is not marked while !gc.", obj_info(obj));
+	}
+
+	/*
+	 * check coloring
+	 *
+	 *               marking:false marking:true
+	 * marked:false  white         *invalid*
+	 * marked:true   black         grey
+	 */
+	if (RVALUE_MARKING_BITMAP(obj)) {
+	    if (!is_marking(objspace) && !RVALUE_MARK_BITMAP(obj)) rb_bug("check_rvalue_consistency: %s is marking, but not marked.", obj_info(obj));
+	}
+    }
+#endif
+    return obj;
+}
+
+static inline int
+RVALUE_MARKED(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_MARK_BITMAP(obj) != 0;
+}
+
+#if USE_RGENGC
+static inline int
+RVALUE_WB_UNPROTECTED(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_WB_UNPROTECTED_BITMAP(obj) != 0;
+}
+
+static inline int
+RVALUE_MARKING(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_MARKING_BITMAP(obj) != 0;
+}
+
+static inline int
+RVALUE_REMEMBERED(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_MARKING_BITMAP(obj) != 0;
+}
+
+static inline int
+RVALUE_LONG_LIVED(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_LONG_LIVED_BITMAP(obj) != 0;
+}
+
+static inline int
+RVALUE_OLD_P_RAW(VALUE obj)
+{
+    const VALUE promoted = FL_PROMOTED0 | FL_PROMOTED1;
+    return (RBASIC(obj)->flags & promoted) == promoted;
+}
+
+static inline int
+RVALUE_OLD_P(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_OLD_P_RAW(obj);
+}
+
+#if RGENGC_CHECK_MODE || GC_DEBUG
+static inline int
+RVALUE_AGE(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    return RVALUE_FLAGS_AGE(RBASIC(obj)->flags);
+}
+#endif
+
+static inline void
+RVALUE_PROMOTE_RAW(rb_objspace_t *objspace, VALUE obj)
+{
+    MARK_IN_BITMAP(GET_HEAP_LONG_LIVED_BITS(obj), obj);
+    objspace->rgengc.old_objects++;
+
+#if RGENGC_PROFILE >= 2
+    objspace->profile.total_promoted_count++;
+    objspace->profile.promoted_types[BUILTIN_TYPE(obj)]++;
+#endif
+}
+
+static inline VALUE
+RVALUE_FLAGS_AGE_SET(VALUE flags, int age)
+{
+    flags &= ~(FL_PROMOTED0 | FL_PROMOTED1);
+    flags |= (age << RVALUE_AGE_SHIFT);
+    return flags;
+}
+
+/* set age to age+1 */
+static inline void
+RVALUE_AGE_INC(rb_objspace_t *objspace, VALUE obj)
+{
+    VALUE flags = RBASIC(obj)->flags;
+    int age = RVALUE_FLAGS_AGE(flags);
+
+    if (RGENGC_CHECK_MODE && age == RVALUE_OLD_AGE) {
+	rb_bug("RVALUE_AGE_INC: can not increment age of OLD object %s.", obj_info(obj));
+    }
+
+    age++;
+    RBASIC(obj)->flags = RVALUE_FLAGS_AGE_SET(flags, age);
+
+    if (age == RVALUE_OLD_AGE) {
+	RVALUE_PROMOTE_RAW(objspace, obj);
+    }
+    check_rvalue_consistency(obj);
+}
+
+/* set age to RVALUE_OLD_AGE */
+static inline void
+RVALUE_AGE_SET_OLD(rb_objspace_t *objspace, VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    if (RGENGC_CHECK_MODE) assert(!RVALUE_OLD_P(obj));
+
+    RBASIC(obj)->flags = RVALUE_FLAGS_AGE_SET(RBASIC(obj)->flags, RVALUE_OLD_AGE);
+    RVALUE_PROMOTE_RAW(objspace, obj);
+
+    check_rvalue_consistency(obj);
+}
+
+/* set age to RVALUE_OLD_AGE - 1 */
+static inline void
+RVALUE_AGE_SET_CANDIDATE(rb_objspace_t *objspace, VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    if (RGENGC_CHECK_MODE) assert(!RVALUE_OLD_P(obj));
+
+    RBASIC(obj)->flags = RVALUE_FLAGS_AGE_SET(RBASIC(obj)->flags, RVALUE_OLD_AGE - 1);
+
+    check_rvalue_consistency(obj);
+}
+
+static inline void
+RVALUE_DEMOTE_RAW(rb_objspace_t *objspace, VALUE obj)
+{
+    RBASIC(obj)->flags = RVALUE_FLAGS_AGE_SET(RBASIC(obj)->flags, 0);
+    CLEAR_IN_BITMAP(GET_HEAP_LONG_LIVED_BITS(obj), obj);
+}
+
+static inline void
+RVALUE_DEMOTE(rb_objspace_t *objspace, VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    if (RGENGC_CHECK_MODE) assert(RVALUE_OLD_P(obj));
+
+    RVALUE_DEMOTE_RAW(objspace, obj);
+
+    if (RVALUE_MARKED(obj)) {
+	objspace->rgengc.old_objects--;
+    }
+
+    check_rvalue_consistency(obj);
+}
+
+static inline void
+RVALUE_AGE_RESET_RAW(VALUE obj)
+{
+    RBASIC(obj)->flags = RVALUE_FLAGS_AGE_SET(RBASIC(obj)->flags, 0);
+}
+
+static inline void
+RVALUE_AGE_RESET(VALUE obj)
+{
+    check_rvalue_consistency(obj);
+    if (RGENGC_CHECK_MODE) assert(!RVALUE_OLD_P(obj));
+    RVALUE_AGE_RESET_RAW(obj);
+    check_rvalue_consistency(obj);
+}
+
+static inline int
+RVALUE_BLACK_P(VALUE obj)
+{
+    return RVALUE_MARKED(obj) && !RVALUE_MARKING(obj);
+}
+
+#if 0
+static inline int
+RVALUE_GREY_P(VALUE obj)
+{
+    return RVALUE_MARKED(obj) && RVALUE_MARKING(obj);
+}
+#endif
+
+static inline int
+RVALUE_WHITE_P(VALUE obj)
+{
+    return RVALUE_MARKED(obj) == FALSE;
+}
+
+#endif /* USE_RGENGC */
+
+/*
+  --------------------------- ObjectSpace -----------------------------
+*/
+
+#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
+rb_objspace_t *
+rb_objspace_alloc(void)
+{
+    rb_objspace_t *objspace = calloc(1, sizeof(rb_objspace_t));
+    malloc_limit = gc_params.malloc_limit_min;
+
+    return objspace;
+}
+#endif
+
+#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
+static void free_stack_chunks(mark_stack_t *);
+static void heap_page_free(rb_objspace_t *objspace, struct heap_page *page);
+
+void
+rb_objspace_free(rb_objspace_t *objspace)
+{
+    if (is_lazy_sweeping(heap_eden))
+	rb_bug("lazy sweeping underway when freeing object space");
+
+    if (objspace->profile.records) {
+	free(objspace->profile.records);
+	objspace->profile.records = 0;
+    }
+
+    if (global_list) {
+	struct gc_list *list, *next;
+	for (list = global_list; list; list = next) {
+	    next = list->next;
+	    xfree(list);
+	}
+    }
+    if (heap_pages_sorted) {
+	size_t i;
+	for (i = 0; i < heap_allocated_pages; ++i) {
+	    heap_page_free(objspace, heap_pages_sorted[i]);
+	}
+	free(heap_pages_sorted);
+	heap_allocated_pages = 0;
+	heap_pages_sorted_length = 0;
+	heap_pages_lomem = 0;
+	heap_pages_himem = 0;
+
+	objspace->eden_heap.page_length = 0;
+	objspace->eden_heap.total_slots = 0;
+	objspace->eden_heap.pages = NULL;
+    }
+    free_stack_chunks(&objspace->mark_stack);
+    free(objspace);
+}
+#endif
+
+static void
+heap_pages_expand_sorted(rb_objspace_t *objspace)
+{
+    size_t next_length = heap_allocatable_pages;
+    next_length += heap_eden->page_length;
+    next_length += heap_tomb->page_length;
+
+    if (next_length > heap_pages_sorted_length) {
+	struct heap_page **sorted;
+	size_t size = next_length * sizeof(struct heap_page *);
+
+	gc_report(3, objspace, "heap_pages_expand_sorted: next_length: %d, size: %d\n", (int)next_length, (int)size);
+
+	if (heap_pages_sorted_length > 0) {
+	    sorted = (struct heap_page **)realloc(heap_pages_sorted, size);
+	    if (sorted) heap_pages_sorted = sorted;
+	}
+	else {
+	    sorted = heap_pages_sorted = (struct heap_page **)malloc(size);
+	}
+
+	if (sorted == 0) {
+	    rb_memerror();
+	}
+
+	heap_pages_sorted_length = next_length;
+    }
+}
+
+static inline void
+heap_page_add_freeobj(rb_objspace_t *objspace, struct heap_page *page, VALUE obj)
+{
+    RVALUE *p = (RVALUE *)obj;
+    p->as.free.flags = 0;
+    p->as.free.next = page->freelist;
+    page->freelist = p;
+
+    if (RGENGC_CHECK_MODE && !is_pointer_to_heap(objspace, p)) {
+	rb_bug("heap_page_add_freeobj: %p is not rvalue.", p);
+    }
+
+    gc_report(3, objspace, "heap_page_add_freeobj: add %p to freelist\n", (void *)obj);
+}
+
+static inline void
+heap_add_freepage(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *page)
+{
+    if (page->freelist) {
+	page->free_next = heap->free_pages;
+	heap->free_pages = page;
+    }
+}
+
+#if GC_ENABLE_INCREMENTAL_MARK
+static inline int
+heap_add_poolpage(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *page)
+{
+    if (page->freelist) {
+	page->free_next = heap->pooled_pages;
+	heap->pooled_pages = page;
+	objspace->rincgc.pooled_slots += page->free_slots;
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+#endif
+
+static void
+heap_unlink_page(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *page)
+{
+    if (page->prev) page->prev->next = page->next;
+    if (page->next) page->next->prev = page->prev;
+    if (heap->pages == page) heap->pages = page->next;
+    page->prev = NULL;
+    page->next = NULL;
+    page->heap = NULL;
+    heap->page_length--;
+    heap->total_slots -= page->total_slots;
+}
+
+static void
+heap_page_free(rb_objspace_t *objspace, struct heap_page *page)
+{
+    heap_allocated_pages--;
+    objspace->profile.total_freed_pages++;
+    aligned_free(page->body);
+    free(page);
+}
+
+static void
+heap_pages_free_unused_pages(rb_objspace_t *objspace)
+{
+    size_t i, j;
+
+    if (heap_tomb->pages && heap_pages_swept_slots > heap_pages_max_free_slots) {
+	for (i = j = 1; j < heap_allocated_pages; i++) {
+	    struct heap_page *page = heap_pages_sorted[i];
+
+	    if (page->heap == heap_tomb && page->free_slots == page->total_slots) {
+		if (heap_pages_swept_slots - page->total_slots > heap_pages_max_free_slots) {
+		    if (0) fprintf(stderr, "heap_pages_free_unused_pages: %d free page %p, heap_pages_swept_slots: %d, heap_pages_max_free_slots: %d\n",
+				   (int)i, page, (int)heap_pages_swept_slots, (int)heap_pages_max_free_slots);
+		    heap_pages_swept_slots -= page->total_slots;
+		    heap_unlink_page(objspace, heap_tomb, page);
+		    heap_page_free(objspace, page);
+		    continue;
+		}
+		else if (i == j) {
+		    return; /* no need to check rest pages */
+		}
+	    }
+	    if (i != j) {
+		heap_pages_sorted[j] = page;
+	    }
+	    j++;
+	}
+	if (RGENGC_CHECK_MODE) assert(j == heap_allocated_pages);
+    }
+}
+
+static struct heap_page *
+heap_page_allocate(rb_objspace_t *objspace)
+{
+    RVALUE *start, *end, *p;
+    struct heap_page *page;
+    struct heap_page_body *page_body = 0;
+    size_t hi, lo, mid;
+    int limit = HEAP_OBJ_LIMIT;
+
+    /* assign heap_page body (contains heap_page_header and RVALUEs) */
+    page_body = (struct heap_page_body *)aligned_malloc(HEAP_ALIGN, HEAP_SIZE);
+    if (page_body == 0) {
+	rb_memerror();
+    }
+
+    /* assign heap_page entry */
+    page = (struct heap_page *)calloc(1, sizeof(struct heap_page));
+    if (page == 0) {
+	aligned_free(page_body);
+	rb_memerror();
+    }
+
+    page->body = page_body;
+
+    /* setup heap_pages_sorted */
+    lo = 0;
+    hi = heap_allocated_pages;
+    while (lo < hi) {
+	struct heap_page *mid_page;
+
+	mid = (lo + hi) / 2;
+	mid_page = heap_pages_sorted[mid];
+	if (mid_page->body < page_body) {
+	    lo = mid + 1;
+	}
+	else if (mid_page->body > page_body) {
+	    hi = mid;
+	}
+	else {
+	    rb_bug("same heap page is allocated: %p at %"PRIuVALUE, (void *)page_body, (VALUE)mid);
+	}
+    }
+    if (hi < heap_allocated_pages) {
+	MEMMOVE(&heap_pages_sorted[hi+1], &heap_pages_sorted[hi], struct heap_page_header*, heap_allocated_pages - hi);
+    }
+
+    heap_pages_sorted[hi] = page;
+
+    heap_allocated_pages++;
+    objspace->profile.total_allocated_pages++;
+
+    if (RGENGC_CHECK_MODE) assert(heap_allocated_pages <= heap_pages_sorted_length);
+
+    /* adjust obj_limit (object number available in this page) */
+    start = (RVALUE*)((VALUE)page_body + sizeof(struct heap_page_header));
+    if ((VALUE)start % sizeof(RVALUE) != 0) {
+	int delta = (int)(sizeof(RVALUE) - ((VALUE)start % sizeof(RVALUE)));
+	start = (RVALUE*)((VALUE)start + delta);
+	limit = (HEAP_SIZE - (int)((VALUE)start - (VALUE)page_body))/(int)sizeof(RVALUE);
+    }
+    end = start + limit;
+
+    if (heap_pages_lomem == 0 || heap_pages_lomem > start) heap_pages_lomem = start;
+    if (heap_pages_himem < end) heap_pages_himem = end;
+
+    page->start = start;
+    page->total_slots = limit;
+    page_body->header.page = page;
+
+    for (p = start; p != end; p++) {
+	gc_report(3, objspace, "assign_heap_page: %p is added to freelist\n", p);
+	heap_page_add_freeobj(objspace, page, (VALUE)p);
+    }
+    page->free_slots = limit;
+
+    return page;
+}
+
+static struct heap_page *
+heap_page_resurrect(rb_objspace_t *objspace)
+{
+    struct heap_page *page;
+
+    if ((page = heap_tomb->pages) != NULL) {
+	heap_unlink_page(objspace, heap_tomb, page);
+	return page;
+    }
+    return NULL;
+}
+
+static struct heap_page *
+heap_page_create(rb_objspace_t *objspace)
+{
+    struct heap_page *page = heap_page_resurrect(objspace);
+    const char *method = "recycle";
+    if (page == NULL) {
+	page = heap_page_allocate(objspace);
+	method = "allocate";
+    }
+    if (0) fprintf(stderr, "heap_page_create: %s - %p, heap_allocated_pages: %d, heap_allocated_pages: %d, tomb->page_length: %d\n",
+		   method, page, (int)heap_pages_sorted_length, (int)heap_allocated_pages, (int)heap_tomb->page_length);
+    return page;
+}
+
+static void
+heap_add_page(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *page)
+{
+    page->heap = heap;
+    page->next = heap->pages;
+    if (heap->pages) heap->pages->prev = page;
+    heap->pages = page;
+    heap->page_length++;
+    heap->total_slots += page->total_slots;
+}
+
+static void
+heap_assign_page(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    struct heap_page *page = heap_page_create(objspace);
+    heap_add_page(objspace, heap, page);
+    heap_add_freepage(objspace, heap, page);
+}
+
+static void
+heap_add_pages(rb_objspace_t *objspace, rb_heap_t *heap, size_t add)
+{
+    size_t i;
+
+    heap_allocatable_pages = add;
+    heap_pages_expand_sorted(objspace);
+    for (i = 0; i < add; i++) {
+	heap_assign_page(objspace, heap);
+    }
+    heap_allocatable_pages = 0;
+}
+
+static size_t
+heap_extend_pages(rb_objspace_t *objspace)
+{
+    size_t used = heap_allocated_pages - heap_tomb->page_length;
+    size_t next_used_limit = (size_t)(used * gc_params.growth_factor);
+
+    if (gc_params.growth_max_slots > 0) {
+	size_t max_used_limit = (size_t)(used + gc_params.growth_max_slots/HEAP_OBJ_LIMIT);
+	if (next_used_limit > max_used_limit) next_used_limit = max_used_limit;
+    }
+
+    return next_used_limit - used;
+}
+
+static void
+heap_set_increment(rb_objspace_t *objspace, size_t additional_pages)
+{
+    size_t used = heap_eden->page_length;
+    size_t next_used_limit = used + additional_pages;
+
+    if (next_used_limit == heap_allocated_pages) next_used_limit++;
+
+    heap_allocatable_pages = next_used_limit - used;
+    heap_pages_expand_sorted(objspace);
+
+    gc_report(1, objspace, "heap_set_increment: heap_allocatable_pages is %d\n", (int)heap_allocatable_pages);
+}
+
+static int
+heap_increment(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    if (heap_allocatable_pages > 0) {
+	gc_report(1, objspace, "heap_increment: heap_pages_sorted_length: %d, heap_pages_inc: %d, heap->page_length: %d\n",
+		  (int)heap_pages_sorted_length, (int)heap_allocatable_pages, (int)heap->page_length);
+	heap_allocatable_pages--;
+	heap_assign_page(objspace, heap);
+	return TRUE;
+    }
+    return FALSE;
+}
+
+static void
+heap_prepare(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    if (RGENGC_CHECK_MODE) assert(heap->free_pages == NULL);
+
+#if GC_ENABLE_LAZY_SWEEP
+    if (is_lazy_sweeping(heap)) {
+	gc_sweep_continue(objspace, heap);
+    }
+#endif
+#if GC_ENABLE_INCREMENTAL_MARK
+    else if (is_incremental_marking(objspace)) {
+	gc_marks_continue(objspace, heap);
+    }
+#endif
+
+    if (heap->free_pages == NULL &&
+	(will_be_incremental_marking(objspace) || heap_increment(objspace, heap) == FALSE) &&
+	gc_start(objspace, FALSE, FALSE, FALSE, GPR_FLAG_NEWOBJ) == FALSE) {
+	rb_memerror();
+    }
+}
+
+static RVALUE *
+heap_get_freeobj_from_next_freepage(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    struct heap_page *page;
+    RVALUE *p;
+
+    while (UNLIKELY(heap->free_pages == NULL)) {
+	heap_prepare(objspace, heap);
+    }
+    page = heap->free_pages;
+    heap->free_pages = page->free_next;
+    heap->using_page = page;
+
+    if (RGENGC_CHECK_MODE) assert(page->free_slots != 0);
+    p = page->freelist;
+    page->freelist = NULL;
+    page->free_slots = 0;
+    return p;
+}
+
+static inline VALUE
+heap_get_freeobj(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    RVALUE *p = heap->freelist;
+
+    while (1) {
+	if (LIKELY(p != NULL)) {
+	    heap->freelist = p->as.free.next;
+	    return (VALUE)p;
+	}
+	else {
+	    p = heap_get_freeobj_from_next_freepage(objspace, heap);
+	}
+    }
+}
+
+void
+rb_objspace_set_event_hook(const rb_event_flag_t event)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    objspace->hook_events = event & RUBY_INTERNAL_EVENT_OBJSPACE_MASK;
+}
+
+static void
+gc_event_hook_body(rb_objspace_t *objspace, const rb_event_flag_t event, VALUE data)
+{
+    rb_thread_t *th = GET_THREAD();
+    EXEC_EVENT_HOOK(th, event, th->cfp->self, 0, 0, data);
+}
+
+#define gc_event_hook(objspace, event, data) do { \
+    if (UNLIKELY((objspace)->hook_events & (event))) { \
+	gc_event_hook_body((objspace), (event), (data)); \
+    } \
+} while (0)
+
+static VALUE
+newobj_of(VALUE klass, VALUE flags, VALUE v1, VALUE v2, VALUE v3)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE obj;
+
+    if (UNLIKELY(during_gc || ruby_gc_stressful)) {
+	if (during_gc) {
+	    dont_gc = 1;
+	    during_gc = 0;
+	    rb_bug("object allocation during garbage collection phase");
+	}
+
+	if (ruby_gc_stressful) {
+	    if (!garbage_collect(objspace, FALSE, FALSE, FALSE, GPR_FLAG_NEWOBJ)) {
+		rb_memerror();
+	    }
+	}
+    }
+
+    obj = heap_get_freeobj(objspace, heap_eden);
+
+    if (RGENGC_CHECK_MODE > 0) assert(BUILTIN_TYPE(obj) == T_NONE);
+
+    /* OBJSETUP */
+    RBASIC(obj)->flags = flags & ~FL_WB_PROTECTED;
+    RBASIC_SET_CLASS_RAW(obj, klass);
+    if (rb_safe_level() >= 3) FL_SET((obj), FL_TAINT);
+    RANY(obj)->as.values.v1 = v1;
+    RANY(obj)->as.values.v2 = v2;
+    RANY(obj)->as.values.v3 = v3;
+
+#if RGENGC_CHECK_MODE
+    assert(RVALUE_MARKED(obj) == FALSE);
+    assert(RVALUE_MARKING(obj) == FALSE);
+    assert(RVALUE_OLD_P(obj) == FALSE);
+    assert(RVALUE_WB_UNPROTECTED(obj) == FALSE);
+
+    if (flags & FL_PROMOTED1) {
+	if (RVALUE_AGE(obj) != 2) rb_bug("newobj: %s of age (%d) != 2.", obj_info(obj), RVALUE_AGE(obj));
+    }
+    else {
+	if (RVALUE_AGE(obj) > 0) rb_bug("newobj: %s of age (%d) > 0.", obj_info(obj), RVALUE_AGE(obj));
+    }
+    if (rgengc_remembered(objspace, (VALUE)obj)) rb_bug("newobj: %s is remembered.", obj_info(obj));
+#endif
+
+#if USE_RGENGC
+    if ((flags & FL_WB_PROTECTED) == 0) {
+	MARK_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(obj), obj);
+    }
+#endif
+
+#if RGENGC_PROFILE
+    if (flags & FL_WB_PROTECTED) {
+	objspace->profile.total_generated_normal_object_count++;
+#if RGENGC_PROFILE >= 2
+	objspace->profile.generated_normal_object_count_types[BUILTIN_TYPE(obj)]++;
+#endif
+    }
+    else {
+	objspace->profile.total_generated_shady_object_count++;
+#if RGENGC_PROFILE >= 2
+	objspace->profile.generated_shady_object_count_types[BUILTIN_TYPE(obj)]++;
+#endif
+    }
+#endif
+
+#if GC_DEBUG
+    RANY(obj)->file = rb_sourcefile();
+    RANY(obj)->line = rb_sourceline();
+    assert(!SPECIAL_CONST_P(obj)); /* check alignment */
+#endif
+
+    objspace->total_allocated_objects++;
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_NEWOBJ, obj);
+    gc_report(5, objspace, "newobj: %s\n", obj_info(obj));
+    return obj;
+}
+
+VALUE
+rb_newobj(void)
+{
+    return newobj_of(0, T_NONE, 0, 0, 0);
+}
+
+VALUE
+rb_newobj_of(VALUE klass, VALUE flags)
+{
+    return newobj_of(klass, flags, 0, 0, 0);
+}
+
+NODE*
+rb_node_newnode(enum node_type type, VALUE a0, VALUE a1, VALUE a2)
+{
+    VALUE flags = (RGENGC_WB_PROTECTED_NODE_CREF && type == NODE_CREF ? FL_WB_PROTECTED : 0);
+    NODE *n = (NODE *)newobj_of(0, T_NODE | flags, a0, a1, a2);
+    nd_set_type(n, type);
+    return n;
+}
+
+VALUE
+rb_data_object_alloc(VALUE klass, void *datap, RUBY_DATA_FUNC dmark, RUBY_DATA_FUNC dfree)
+{
+    if (klass) Check_Type(klass, T_CLASS);
+    return newobj_of(klass, T_DATA, (VALUE)dmark, (VALUE)dfree, (VALUE)datap);
+}
+
+VALUE
+rb_data_typed_object_alloc(VALUE klass, void *datap, const rb_data_type_t *type)
+{
+    if (klass) Check_Type(klass, T_CLASS);
+    return newobj_of(klass, T_DATA | (type->flags & ~T_MASK), (VALUE)type, (VALUE)1, (VALUE)datap);
+}
+
+size_t
+rb_objspace_data_type_memsize(VALUE obj)
+{
+    if (RTYPEDDATA_P(obj) && RTYPEDDATA_TYPE(obj)->function.dsize) {
+	return RTYPEDDATA_TYPE(obj)->function.dsize(RTYPEDDATA_DATA(obj));
+    }
+    else {
+	return 0;
+    }
+}
+
+const char *
+rb_objspace_data_type_name(VALUE obj)
+{
+    if (RTYPEDDATA_P(obj)) {
+	return RTYPEDDATA_TYPE(obj)->wrap_struct_name;
+    }
+    else {
+	return 0;
+    }
+}
+
+static inline int
+is_pointer_to_heap(rb_objspace_t *objspace, void *ptr)
+{
+    register RVALUE *p = RANY(ptr);
+    register struct heap_page *page;
+    register size_t hi, lo, mid;
+
+    if (p < heap_pages_lomem || p > heap_pages_himem) return FALSE;
+    if ((VALUE)p % sizeof(RVALUE) != 0) return FALSE;
+
+    /* check if p looks like a pointer using bsearch*/
+    lo = 0;
+    hi = heap_allocated_pages;
+    while (lo < hi) {
+	mid = (lo + hi) / 2;
+	page = heap_pages_sorted[mid];
+	if (page->start <= p) {
+	    if (p < page->start + page->total_slots) {
+		return TRUE;
+	    }
+	    lo = mid + 1;
+	}
+	else {
+	    hi = mid;
+	}
+    }
+    return FALSE;
+}
+
+static int
+free_method_entry_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    rb_method_entry_t *me = (rb_method_entry_t *)value;
+    if (!me->mark) {
+	rb_free_method_entry(me);
+    }
+    return ST_CONTINUE;
+}
+
+static void
+rb_free_m_tbl(st_table *tbl)
+{
+    st_foreach(tbl, free_method_entry_i, 0);
+    st_free_table(tbl);
+}
+
+void
+rb_free_m_tbl_wrapper(struct method_table_wrapper *wrapper)
+{
+    if (wrapper->tbl) {
+	rb_free_m_tbl(wrapper->tbl);
+    }
+    xfree(wrapper);
+}
+
+static int
+free_const_entry_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    rb_const_entry_t *ce = (rb_const_entry_t *)value;
+    xfree(ce);
+    return ST_CONTINUE;
+}
+
+void
+rb_free_const_table(st_table *tbl)
+{
+    st_foreach(tbl, free_const_entry_i, 0);
+    st_free_table(tbl);
+}
+
+static inline void
+make_zombie(rb_objspace_t *objspace, VALUE obj, void (*dfree)(void *), void *data)
+{
+    struct RZombie *zombie = RZOMBIE(obj);
+    zombie->basic.flags = T_ZOMBIE;
+    zombie->dfree = dfree;
+    zombie->data = data;
+    zombie->next = heap_pages_deferred_final;
+    heap_pages_deferred_final = (VALUE)zombie;
+}
+
+static inline void
+make_io_zombie(rb_objspace_t *objspace, VALUE obj)
+{
+    rb_io_t *fptr = RANY(obj)->as.file.fptr;
+    make_zombie(objspace, obj, (void (*)(void*))rb_io_fptr_finalize, fptr);
+}
+
+static int
+obj_free(rb_objspace_t *objspace, VALUE obj)
+{
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_FREEOBJ, 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);
+    }
+
+#if USE_RGENGC
+    if (RVALUE_WB_UNPROTECTED(obj)) CLEAR_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(obj), obj);
+
+#if RGENGC_CHECK_MODE
+#define CHECK(x) if (x(obj) != FALSE) rb_bug("obj_free: " #x "(%s) != FALSE", obj_info(obj))
+	CHECK(RVALUE_WB_UNPROTECTED);
+	CHECK(RVALUE_MARKED);
+	CHECK(RVALUE_MARKING);
+	CHECK(RVALUE_LONG_LIVED);
+#undef CHECK
+#endif
+#endif
+
+    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:
+        if (RCLASS_M_TBL_WRAPPER(obj)) {
+            rb_free_m_tbl_wrapper(RCLASS_M_TBL_WRAPPER(obj));
+        }
+	if (RCLASS_IV_TBL(obj)) {
+	    st_free_table(RCLASS_IV_TBL(obj));
+	}
+	if (RCLASS_CONST_TBL(obj)) {
+	    rb_free_const_table(RCLASS_CONST_TBL(obj));
+	}
+	if (RCLASS_IV_INDEX_TBL(obj)) {
+	    st_free_table(RCLASS_IV_INDEX_TBL(obj));
+	}
+	if (RCLASS_EXT(obj)->subclasses) {
+	    if (BUILTIN_TYPE(obj) == T_MODULE) {
+		rb_class_detach_module_subclasses(obj);
+	    }
+	    else {
+		rb_class_detach_subclasses(obj);
+	    }
+	    RCLASS_EXT(obj)->subclasses = NULL;
+	}
+	rb_class_remove_from_module_subclasses(obj);
+	rb_class_remove_from_super_subclasses(obj);
+	if (RANY(obj)->as.klass.ptr)
+	    xfree(RANY(obj)->as.klass.ptr);
+	RANY(obj)->as.klass.ptr = NULL;
+	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)) {
+	    int free_immediately = FALSE;
+	    void (*dfree)(void *);
+	    void *data = DATA_PTR(obj);
+
+	    if (RTYPEDDATA_P(obj)) {
+		free_immediately = (RANY(obj)->as.typeddata.type->flags & RUBY_TYPED_FREE_IMMEDIATELY) != 0;
+		dfree = RANY(obj)->as.typeddata.type->function.dfree;
+		if (0 && free_immediately == 0) {
+		    /* to expose non-free-immediate T_DATA */
+		    fprintf(stderr, "not immediate -> %s\n", RANY(obj)->as.typeddata.type->wrap_struct_name);
+		}
+	    }
+	    else {
+		dfree = RANY(obj)->as.data.dfree;
+	    }
+
+	    if (dfree) {
+		if (dfree == RUBY_DEFAULT_FREE) {
+		    xfree(data);
+		}
+		else if (free_immediately) {
+		    (*dfree)(data);
+		}
+		else {
+		    make_zombie(objspace, obj, dfree, data);
+		    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_zombie(objspace, obj);
+	    return 1;
+	}
+	break;
+      case T_RATIONAL:
+      case T_COMPLEX:
+	break;
+      case T_ICLASS:
+	/* iClass shares table with the module */
+	if (RCLASS_EXT(obj)->subclasses) {
+	    rb_class_detach_subclasses(obj);
+	    RCLASS_EXT(obj)->subclasses = NULL;
+	}
+	rb_class_remove_from_module_subclasses(obj);
+	rb_class_remove_from_super_subclasses(obj);
+	xfree(RANY(obj)->as.klass.ptr);
+	RANY(obj)->as.klass.ptr = NULL;
+	break;
+
+      case T_FLOAT:
+	break;
+
+      case T_BIGNUM:
+	if (!(RBASIC(obj)->flags & BIGNUM_EMBED_FLAG) && BIGNUM_DIGITS(obj)) {
+	    xfree(BIGNUM_DIGITS(obj));
+	}
+	break;
+
+      case T_NODE:
+	rb_gc_free_node(obj);
+	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((void *)RANY(obj)->as.rstruct.as.heap.ptr);
+	}
+	break;
+
+      case T_SYMBOL:
+	{
+            rb_gc_free_dsymbol(obj);
+	}
+	break;
+
+      default:
+	rb_bug("gc_sweep(): unknown data type 0x%x(%p) 0x%"PRIxVALUE,
+	       BUILTIN_TYPE(obj), (void*)obj, RBASIC(obj)->flags);
+    }
+
+    if (FL_TEST(obj, FL_FINALIZE)) {
+	make_zombie(objspace, obj, 0, 0);
+	return 1;
+    }
+    else {
+	return 0;
+    }
+}
+
+void
+Init_heap(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    gc_stress_set(objspace, ruby_initial_gc_stress);
+
+#if RGENGC_ESTIMATE_OLDMALLOC
+    objspace->rgengc.oldmalloc_increase_limit = gc_params.oldmalloc_limit_min;
+#endif
+
+    heap_add_pages(objspace, heap_eden, gc_params.heap_init_slots / HEAP_OBJ_LIMIT);
+    init_mark_stack(&objspace->mark_stack);
+
+#ifdef USE_SIGALTSTACK
+    {
+	/* altstack of another threads are allocated in another place */
+	rb_thread_t *th = GET_THREAD();
+	void *tmp = th->altstack;
+	th->altstack = malloc(rb_sigaltstack_size());
+	free(tmp); /* free previously allocated area */
+    }
+#endif
+
+    objspace->profile.invoke_time = getrusage_time();
+    finalizer_table = st_init_numtable();
+}
+
+typedef int each_obj_callback(void *, void *, size_t, void *);
+
+struct each_obj_args {
+    each_obj_callback *callback;
+    void *data;
+};
+
+static VALUE
+objspace_each_objects(VALUE arg)
+{
+    size_t i;
+    struct heap_page_body *last_body = 0;
+    struct heap_page *page;
+    RVALUE *pstart, *pend;
+    rb_objspace_t *objspace = &rb_objspace;
+    struct each_obj_args *args = (struct each_obj_args *)arg;
+
+    i = 0;
+    while (i < heap_allocated_pages) {
+	while (0 < i && last_body < heap_pages_sorted[i-1]->body)              i--;
+	while (i < heap_allocated_pages && heap_pages_sorted[i]->body <= last_body) i++;
+	if (heap_allocated_pages <= i) break;
+
+	page = heap_pages_sorted[i];
+	last_body = page->body;
+
+	pstart = page->start;
+	pend = pstart + page->total_slots;
+
+	if ((*args->callback)(pstart, pend, sizeof(RVALUE), args->data)) {
+	    break;
+	}
+    }
+
+    return Qnil;
+}
+
+static VALUE
+incremental_enable(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    objspace->flags.dont_incremental = FALSE;
+    return Qnil;
+}
+
+/*
+ * rb_objspace_each_objects() is special C API to walk through
+ * Ruby object space.  This C API is too difficult to use it.
+ * To be frank, you should not use it. Or you need to read the
+ * source code of this function and understand what this function does.
+ *
+ * 'callback' will be called several times (the number of heap page,
+ * at current implementation) with:
+ *   vstart: a pointer to the first living object of the heap_page.
+ *   vend: a pointer to next to the valid heap_page 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_page.  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 page
+ *       including freed object page.
+ *
+ * Note: On this implementation, 'stride' is same as sizeof(RVALUE).
+ *       However, there are possibilities to pass variable values with
+ *       'stride' with some reasons.  You must use stride instead of
+ *       use some constant value in the iteration.
+ */
+void
+rb_objspace_each_objects(each_obj_callback *callback, void *data)
+{
+    struct each_obj_args args;
+    rb_objspace_t *objspace = &rb_objspace;
+    int prev_dont_incremental = objspace->flags.dont_incremental;
+
+    gc_rest(objspace);
+    objspace->flags.dont_incremental = TRUE;
+
+    args.callback = callback;
+    args.data = data;
+
+    if (prev_dont_incremental) {
+	objspace_each_objects((VALUE)&args);
+    }
+    else {
+	rb_ensure(objspace_each_objects, (VALUE)&args, incremental_enable, Qnil);
+    }
+}
+
+void
+rb_objspace_each_objects_without_setup(each_obj_callback *callback, void *data)
+{
+    struct each_obj_args args;
+    args.callback = callback;
+    args.data = data;
+
+    objspace_each_objects((VALUE)&args);
+}
+
+struct os_each_struct {
+    size_t num;
+    VALUE of;
+};
+
+static int
+internal_object_p(VALUE obj)
+{
+    RVALUE *p = (RVALUE *)obj;
+
+    if (p->as.basic.flags) {
+	switch (BUILTIN_TYPE(p)) {
+	  case T_NONE:
+	  case T_ICLASS:
+	  case T_NODE:
+	  case T_ZOMBIE:
+	    break;
+	  case T_CLASS:
+	    if (FL_TEST(p, FL_SINGLETON))
+	      break;
+	  default:
+	    if (!p->as.basic.klass) break;
+	    return 0;
+	}
+    }
+    return 1;
+}
+
+int
+rb_objspace_internal_object_p(VALUE obj)
+{
+    return internal_object_p(obj);
+}
+
+static int
+os_obj_of_i(void *vstart, void *vend, size_t stride, void *data)
+{
+    struct os_each_struct *oes = (struct os_each_struct *)data;
+    RVALUE *p = (RVALUE *)vstart, *pend = (RVALUE *)vend;
+
+    for (; p != pend; p++) {
+	volatile VALUE v = (VALUE)p;
+	if (!internal_object_p(v)) {
+	    if (!oes->of || rb_obj_is_kind_of(v, oes->of)) {
+		rb_yield(v);
+		oes->num++;
+	    }
+	}
+    }
+
+    return 0;
+}
+
+static VALUE
+os_obj_of(VALUE of)
+{
+    struct os_each_struct oes;
+
+    oes.num = 0;
+    oes.of = of;
+    rb_objspace_each_objects(os_obj_of_i, &oes);
+    return SIZET2NUM(oes.num);
+}
+
+/*
+ *  call-seq:
+ *     ObjectSpace.each_object([module]) {|obj| ... } -> fixnum
+ *     ObjectSpace.each_object([module])              -> an_enumerator
+ *
+ *  Calls the block once for each living, nonimmediate object in this
+ *  Ruby process. If <i>module</i> is specified, calls the block
+ *  for only those classes or modules that match (or are a subclass of)
+ *  <i>module</i>. Returns the number of objects found. Immediate
+ *  objects (<code>Fixnum</code>s, <code>Symbol</code>s
+ *  <code>true</code>, <code>false</code>, and <code>nil</code>) are
+ *  never returned. In the example below, <code>each_object</code>
+ *  returns both the numbers we defined and several constants defined in
+ *  the <code>Math</code> module.
+ *
+ *  If no block is given, an enumerator is returned instead.
+ *
+ *     a = 102.7
+ *     b = 95       # Won't be returned
+ *     c = 12345678987654321
+ *     count = ObjectSpace.each_object(Numeric) {|x| p x }
+ *     puts "Total count: #{count}"
+ *
+ *  <em>produces:</em>
+ *
+ *     12345678987654321
+ *     102.7
+ *     2.71828182845905
+ *     3.14159265358979
+ *     2.22044604925031e-16
+ *     1.7976931348623157e+308
+ *     2.2250738585072e-308
+ *     Total count: 7
+ *
+ */
+
+static VALUE
+os_each_obj(int argc, VALUE *argv, VALUE os)
+{
+    VALUE of;
+
+    if (argc == 0) {
+	of = 0;
+    }
+    else {
+	rb_scan_args(argc, argv, "01", &of);
+    }
+    RETURN_ENUMERATOR(os, 1, &of);
+    return os_obj_of(of);
+}
+
+/*
+ *  call-seq:
+ *     ObjectSpace.undefine_finalizer(obj)
+ *
+ *  Removes all finalizers for <i>obj</i>.
+ *
+ */
+
+static VALUE
+undefine_final(VALUE os, VALUE obj)
+{
+    return rb_undefine_finalizer(obj);
+}
+
+VALUE
+rb_undefine_finalizer(VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    st_data_t data = obj;
+    rb_check_frozen(obj);
+    st_delete(finalizer_table, &data, 0);
+    FL_UNSET(obj, FL_FINALIZE);
+    return obj;
+}
+
+static void
+should_be_callable(VALUE block)
+{
+    if (!rb_obj_respond_to(block, rb_intern("call"), TRUE)) {
+	rb_raise(rb_eArgError, "wrong type argument %"PRIsVALUE" (should be callable)",
+		 rb_obj_class(block));
+    }
+}
+static void
+should_be_finalizable(VALUE obj)
+{
+    if (!FL_ABLE(obj)) {
+	rb_raise(rb_eArgError, "cannot define finalizer for %s",
+		 rb_obj_classname(obj));
+    }
+    rb_check_frozen(obj);
+}
+
+/*
+ *  call-seq:
+ *     ObjectSpace.define_finalizer(obj, aProc=proc())
+ *
+ *  Adds <i>aProc</i> as a finalizer, to be called after <i>obj</i>
+ *  was destroyed.
+ *
+ */
+
+static VALUE
+define_final(int argc, VALUE *argv, VALUE os)
+{
+    VALUE obj, block;
+
+    rb_scan_args(argc, argv, "11", &obj, &block);
+    should_be_finalizable(obj);
+    if (argc == 1) {
+	block = rb_block_proc();
+    }
+    else {
+	should_be_callable(block);
+    }
+
+    return define_final0(obj, block);
+}
+
+static VALUE
+define_final0(VALUE obj, VALUE block)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE table;
+    st_data_t data;
+
+    RBASIC(obj)->flags |= FL_FINALIZE;
+
+    block = rb_ary_new3(2, INT2FIX(rb_safe_level()), block);
+    OBJ_FREEZE(block);
+
+    if (st_lookup(finalizer_table, obj, &data)) {
+	table = (VALUE)data;
+
+	/* avoid duplicate block, table is usually small */
+	{
+	    const VALUE *ptr = RARRAY_CONST_PTR(table);
+	    long len = RARRAY_LEN(table);
+	    long i;
+
+	    for (i = 0; i < len; i++, ptr++) {
+		if (rb_funcall(*ptr, idEq, 1, block)) {
+		    return *ptr;
+		}
+	    }
+	}
+
+	rb_ary_push(table, block);
+    }
+    else {
+	table = rb_ary_new3(1, block);
+	RBASIC_CLEAR_CLASS(table);
+	st_add_direct(finalizer_table, obj, table);
+    }
+    return block;
+}
+
+VALUE
+rb_define_finalizer(VALUE obj, VALUE block)
+{
+    should_be_finalizable(obj);
+    should_be_callable(block);
+    return define_final0(obj, block);
+}
+
+void
+rb_gc_copy_finalizer(VALUE dest, VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE table;
+    st_data_t data;
+
+    if (!FL_TEST(obj, FL_FINALIZE)) return;
+    if (st_lookup(finalizer_table, obj, &data)) {
+	table = (VALUE)data;
+	st_insert(finalizer_table, dest, table);
+    }
+    FL_SET(dest, FL_FINALIZE);
+}
+
+static VALUE
+run_single_final(VALUE arg)
+{
+    VALUE *args = (VALUE *)arg;
+    rb_eval_cmd(args[0], args[1], (int)args[2]);
+    return Qnil;
+}
+
+static void
+run_finalizer(rb_objspace_t *objspace, VALUE obj, VALUE table)
+{
+    long i;
+    int status;
+    VALUE args[3];
+    VALUE objid = nonspecial_obj_id(obj);
+
+    if (RARRAY_LEN(table) > 0) {
+	args[1] = rb_obj_freeze(rb_ary_new3(1, objid));
+    }
+    else {
+	args[1] = 0;
+    }
+
+    args[2] = (VALUE)rb_safe_level();
+    for (i=0; i<RARRAY_LEN(table); i++) {
+	VALUE final = RARRAY_AREF(table, i);
+	args[0] = RARRAY_AREF(final, 1);
+	args[2] = FIX2INT(RARRAY_AREF(final, 0));
+	status = 0;
+	rb_protect(run_single_final, (VALUE)args, &status);
+	if (status)
+	    rb_set_errinfo(Qnil);
+    }
+}
+
+static void
+run_final(rb_objspace_t *objspace, VALUE zombie)
+{
+    st_data_t key, table;
+
+    if (RZOMBIE(zombie)->dfree) {
+	RZOMBIE(zombie)->dfree(RZOMBIE(zombie)->data);
+    }
+
+    key = (st_data_t)zombie;
+    if (st_delete(finalizer_table, &key, &table)) {
+	run_finalizer(objspace, zombie, (VALUE)table);
+    }
+}
+
+static void
+finalize_list(rb_objspace_t *objspace, VALUE zombie)
+{
+    while (zombie) {
+	VALUE next_zombie = RZOMBIE(zombie)->next;
+	struct heap_page *page = GET_HEAP_PAGE(zombie);
+
+	run_final(objspace, zombie);
+
+	RZOMBIE(zombie)->basic.flags = 0;
+	heap_pages_final_slots--;
+	page->final_slots--;
+	page->free_slots++;
+	heap_page_add_freeobj(objspace, GET_HEAP_PAGE(zombie), zombie);
+
+	heap_pages_swept_slots++;
+	objspace->profile.total_freed_objects++;
+
+	zombie = next_zombie;
+    }
+}
+
+static void
+finalize_deferred(rb_objspace_t *objspace)
+{
+    VALUE zombie;
+
+    while ((zombie = (VALUE)ATOMIC_PTR_EXCHANGE(heap_pages_deferred_final, 0)) != 0) {
+	finalize_list(objspace, zombie);
+    }
+}
+
+static void
+gc_finalize_deferred(void *dmy)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    if (ATOMIC_EXCHANGE(finalizing, 1)) return;
+    finalize_deferred(objspace);
+    ATOMIC_SET(finalizing, 0);
+}
+
+/* TODO: to keep compatibility, maybe unused. */
+void
+rb_gc_finalize_deferred(void)
+{
+    gc_finalize_deferred(0);
+}
+
+static void
+gc_finalize_deferred_register(void)
+{
+    if (rb_postponed_job_register_one(0, gc_finalize_deferred, 0) == 0) {
+	rb_bug("gc_finalize_deferred_register: can't register finalizer.");
+    }
+}
+
+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)
+{
+#if RGENGC_CHECK_MODE >= 2
+    gc_verify_internal_consistency(Qnil);
+#endif
+    rb_objspace_call_finalizer(&rb_objspace);
+}
+
+static void
+rb_objspace_call_finalizer(rb_objspace_t *objspace)
+{
+    RVALUE *p, *pend;
+    size_t i;
+
+    gc_rest(objspace);
+
+    if (ATOMIC_EXCHANGE(finalizing, 1)) return;
+
+    /* run finalizers */
+    finalize_deferred(objspace);
+    assert(heap_pages_deferred_final == 0);
+
+    gc_rest(objspace);
+    /* prohibit incremental GC */
+    objspace->flags.dont_incremental = 1;
+
+    /* force to run finalizer */
+    while (finalizer_table->num_entries) {
+	struct force_finalize_list *list = 0;
+	st_foreach(finalizer_table, force_chain_object, (st_data_t)&list);
+	while (list) {
+	    struct force_finalize_list *curr = list;
+	    st_data_t obj = (st_data_t)curr->obj;
+	    run_finalizer(objspace, curr->obj, curr->table);
+	    st_delete(finalizer_table, &obj, 0);
+	    list = curr->next;
+	    xfree(curr);
+	}
+    }
+
+    /* prohibit GC because force T_DATA finalizers can break an object graph consistency */
+    dont_gc = 1;
+
+    /* running data/file finalizers are part of garbage collection */
+    gc_enter(objspace, "rb_objspace_call_finalizer");
+
+    /* run data/file object's finalizers */
+    for (i = 0; i < heap_allocated_pages; i++) {
+	p = heap_pages_sorted[i]->start; pend = p + heap_pages_sorted[i]->total_slots;
+	while (p < pend) {
+	    switch (BUILTIN_TYPE(p)) {
+	      case T_DATA:
+		if (!DATA_PTR(p) || !RANY(p)->as.data.dfree) break;
+		if (rb_obj_is_thread((VALUE)p)) break;
+		if (rb_obj_is_mutex((VALUE)p)) break;
+		if (rb_obj_is_fiber((VALUE)p)) break;
+		p->as.free.flags = 0;
+		if (RTYPEDDATA_P(p)) {
+		    RDATA(p)->dfree = RANY(p)->as.typeddata.type->function.dfree;
+		}
+		if (RANY(p)->as.data.dfree == (RUBY_DATA_FUNC)-1) {
+		    xfree(DATA_PTR(p));
+		}
+		else if (RANY(p)->as.data.dfree) {
+		    make_zombie(objspace, (VALUE)p, RANY(p)->as.data.dfree, RANY(p)->as.data.data);
+		}
+		break;
+	      case T_FILE:
+		if (RANY(p)->as.file.fptr) {
+		    make_io_zombie(objspace, (VALUE)p);
+		}
+		break;
+	    }
+	    p++;
+	}
+    }
+
+    gc_exit(objspace, "rb_objspace_call_finalizer");
+
+    if (heap_pages_deferred_final) {
+	finalize_list(objspace, heap_pages_deferred_final);
+    }
+
+    st_free_table(finalizer_table);
+    finalizer_table = 0;
+    ATOMIC_SET(finalizing, 0);
+}
+
+static inline int
+is_id_value(rb_objspace_t *objspace, VALUE ptr)
+{
+    if (!is_pointer_to_heap(objspace, (void *)ptr)) return FALSE;
+    if (BUILTIN_TYPE(ptr) > T_FIXNUM) return FALSE;
+    if (BUILTIN_TYPE(ptr) == T_ICLASS) return FALSE;
+    return TRUE;
+}
+
+static inline int
+heap_is_swept_object(rb_objspace_t *objspace, rb_heap_t *heap, VALUE ptr)
+{
+    struct heap_page *page = GET_HEAP_PAGE(ptr);
+    return page->flags.before_sweep ? FALSE : TRUE;
+}
+
+static inline int
+is_swept_object(rb_objspace_t *objspace, VALUE ptr)
+{
+    if (heap_is_swept_object(objspace, heap_eden, ptr)) {
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+
+/* garbage objects will be collected soon. */
+static inline int
+is_garbage_object(rb_objspace_t *objspace, VALUE ptr)
+{
+    if (!is_lazy_sweeping(heap_eden) ||
+	is_swept_object(objspace, ptr) ||
+	MARKED_IN_BITMAP(GET_HEAP_MARK_BITS(ptr), ptr)) {
+
+	return FALSE;
+    }
+    else {
+	return TRUE;
+    }
+}
+
+static inline int
+is_live_object(rb_objspace_t *objspace, VALUE ptr)
+{
+    switch (BUILTIN_TYPE(ptr)) {
+      case T_NONE:
+      case T_ZOMBIE:
+	return FALSE;
+    }
+
+    if (!is_garbage_object(objspace, ptr)) {
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+
+static inline int
+is_markable_object(rb_objspace_t *objspace, VALUE obj)
+{
+    if (rb_special_const_p(obj)) return FALSE; /* special const is not markable */
+    check_rvalue_consistency(obj);
+    return TRUE;
+}
+
+int
+rb_objspace_markable_object_p(VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    return is_markable_object(objspace, obj) && is_live_object(objspace, obj);
+}
+
+int
+rb_objspace_garbage_object_p(VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    return is_garbage_object(objspace, obj);
+}
+
+/*
+ *  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;
+
+    ptr = NUM2PTR(objid);
+    p0 = (void *)ptr;
+
+    if (ptr == Qtrue) return Qtrue;
+    if (ptr == Qfalse) return Qfalse;
+    if (ptr == Qnil) return Qnil;
+    if (FIXNUM_P(ptr)) return (VALUE)ptr;
+    if (FLONUM_P(ptr)) return (VALUE)ptr;
+    ptr = obj_id_to_ref(objid);
+
+    if ((ptr % sizeof(RVALUE)) == (4 << 2)) {
+        ID symid = ptr / sizeof(RVALUE);
+        if (rb_id2str(symid) == 0)
+	    rb_raise(rb_eRangeError, "%p is not symbol id value", p0);
+	return ID2SYM(symid);
+    }
+
+    if (!is_id_value(objspace, ptr)) {
+	rb_raise(rb_eRangeError, "%p is not id value", p0);
+    }
+    if (!is_live_object(objspace, ptr)) {
+	rb_raise(rb_eRangeError, "%p is recycled object", p0);
+    }
+    if (RBASIC(ptr)->klass == 0) {
+	rb_raise(rb_eRangeError, "%p is internal object", p0);
+    }
+    return (VALUE)ptr;
+}
+
+/*
+ *  Document-method: __id__
+ *  Document-method: object_id
+ *
+ *  call-seq:
+ *     obj.__id__       -> integer
+ *     obj.object_id    -> integer
+ *
+ *  Returns an integer identifier for +obj+.
+ *
+ *  The same number will be returned on all calls to +object_id+ for a given
+ *  object, and no two active objects will share an id.
+ *
+ *  Note: that some objects of builtin classes are reused for optimization.
+ *  This is the case for immediate values and frozen string literals.
+ *
+ *  Immediate values are not passed by reference but are passed by value:
+ *  +nil+, +true+, +false+, Fixnums, Symbols, and some Floats.
+ *
+ *      Object.new.object_id  == Object.new.object_id  # => false
+ *      (21 * 2).object_id    == (21 * 2).object_id    # => true
+ *      "hello".object_id     == "hello".object_id     # => false
+ *      "hi".freeze.object_id == "hi".freeze.object_id # => true
+ */
+
+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 (STATIC_SYM_P(obj)) {
+        return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG;
+    }
+    else if (FLONUM_P(obj)) {
+#if SIZEOF_LONG == SIZEOF_VOIDP
+	return LONG2NUM((SIGNED_VALUE)obj);
+#else
+	return LL2NUM((SIGNED_VALUE)obj);
+#endif
+    }
+    else if (SPECIAL_CONST_P(obj)) {
+	return LONG2NUM((SIGNED_VALUE)obj);
+    }
+    return nonspecial_obj_id(obj);
+}
+
+#include "regint.h"
+
+static size_t
+obj_memsize_of(VALUE obj, int use_all_types)
+{
+    size_t size = 0;
+
+    if (SPECIAL_CONST_P(obj)) {
+	return 0;
+    }
+
+    if (FL_TEST(obj, FL_EXIVAR)) {
+	size += rb_generic_ivar_memsize(obj);
+    }
+
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+	if (!(RBASIC(obj)->flags & ROBJECT_EMBED) &&
+	    ROBJECT(obj)->as.heap.ivptr) {
+	    size += ROBJECT(obj)->as.heap.numiv * sizeof(VALUE);
+	}
+	break;
+      case T_MODULE:
+      case T_CLASS:
+	if (RCLASS_M_TBL_WRAPPER(obj)) {
+	    size += sizeof(struct method_table_wrapper);
+	}
+	if (RCLASS_M_TBL(obj)) {
+	    size += st_memsize(RCLASS_M_TBL(obj));
+	}
+	if (RCLASS_EXT(obj)) {
+	    if (RCLASS_IV_TBL(obj)) {
+		size += st_memsize(RCLASS_IV_TBL(obj));
+	    }
+	    if (RCLASS_IV_INDEX_TBL(obj)) {
+		size += st_memsize(RCLASS_IV_INDEX_TBL(obj));
+	    }
+	    if (RCLASS(obj)->ptr->iv_tbl) {
+		size += st_memsize(RCLASS(obj)->ptr->iv_tbl);
+	    }
+	    if (RCLASS(obj)->ptr->const_tbl) {
+		size += st_memsize(RCLASS(obj)->ptr->const_tbl);
+	    }
+	    size += sizeof(rb_classext_t);
+	}
+	break;
+      case T_STRING:
+	size += rb_str_memsize(obj);
+	break;
+      case T_ARRAY:
+	size += rb_ary_memsize(obj);
+	break;
+      case T_HASH:
+	if (RHASH(obj)->ntbl) {
+	    size += st_memsize(RHASH(obj)->ntbl);
+	}
+	break;
+      case T_REGEXP:
+	if (RREGEXP(obj)->ptr) {
+	    size += onig_memsize(RREGEXP(obj)->ptr);
+	}
+	break;
+      case T_DATA:
+	if (use_all_types) size += rb_objspace_data_type_memsize(obj);
+	break;
+      case T_MATCH:
+	if (RMATCH(obj)->rmatch) {
+            struct rmatch *rm = RMATCH(obj)->rmatch;
+	    size += onig_region_memsize(&rm->regs);
+	    size += sizeof(struct rmatch_offset) * rm->char_offset_num_allocated;
+	    size += sizeof(struct rmatch);
+	}
+	break;
+      case T_FILE:
+	if (RFILE(obj)->fptr) {
+	    size += rb_io_memsize(RFILE(obj)->fptr);
+	}
+	break;
+      case T_RATIONAL:
+      case T_COMPLEX:
+	break;
+      case T_ICLASS:
+	/* iClass shares table with the module */
+	break;
+
+      case T_FLOAT:
+      case T_SYMBOL:
+	break;
+
+      case T_BIGNUM:
+	if (!(RBASIC(obj)->flags & BIGNUM_EMBED_FLAG) && BIGNUM_DIGITS(obj)) {
+	    size += BIGNUM_LEN(obj) * sizeof(BDIGIT);
+	}
+	break;
+
+      case T_NODE:
+	if (use_all_types) size += rb_node_memsize(obj);
+	break;
+
+      case T_STRUCT:
+	if ((RBASIC(obj)->flags & RSTRUCT_EMBED_LEN_MASK) == 0 &&
+	    RSTRUCT(obj)->as.heap.ptr) {
+	    size += sizeof(VALUE) * RSTRUCT_LEN(obj);
+	}
+	break;
+
+      case T_ZOMBIE:
+	break;
+
+      default:
+	rb_bug("objspace/memsize_of(): unknown data type 0x%x(%p)",
+	       BUILTIN_TYPE(obj), (void*)obj);
+    }
+
+    return size + sizeof(RVALUE);
+}
+
+size_t
+rb_obj_memsize_of(VALUE obj)
+{
+    return obj_memsize_of(obj, TRUE);
+}
+
+static int
+set_zero(st_data_t key, st_data_t val, st_data_t arg)
+{
+    VALUE k = (VALUE)key;
+    VALUE hash = (VALUE)arg;
+    rb_hash_aset(hash, k, INT2FIX(0));
+    return ST_CONTINUE;
+}
+
+/*
+ *  call-seq:
+ *     ObjectSpace.count_objects([result_hash]) -> hash
+ *
+ *  Counts objects for each type.
+ *
+ *  It returns a hash, such as:
+ *	{
+ *	  :TOTAL=>10000,
+ *	  :FREE=>3011,
+ *	  :T_OBJECT=>6,
+ *	  :T_CLASS=>404,
+ *	  # ...
+ *	}
+ *
+ *  The contents of the returned hash are implementation specific.
+ *  It may be changed in future.
+ *
+ *  If the optional argument +result_hash+ is given,
+ *  it is overwritten and returned. This is intended to avoid probe effect.
+ *
+ *  This method is only expected to work on C Ruby.
+ *
+ */
+
+static VALUE
+count_objects(int argc, VALUE *argv, VALUE os)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    size_t counts[T_MASK+1];
+    size_t freed = 0;
+    size_t total = 0;
+    size_t i;
+    VALUE hash;
+
+    if (rb_scan_args(argc, argv, "01", &hash) == 1) {
+        if (!RB_TYPE_P(hash, T_HASH))
+            rb_raise(rb_eTypeError, "non-hash given");
+    }
+
+    for (i = 0; i <= T_MASK; i++) {
+        counts[i] = 0;
+    }
+
+    for (i = 0; i < heap_allocated_pages; i++) {
+	struct heap_page *page = heap_pages_sorted[i];
+	RVALUE *p, *pend;
+
+	p = page->start; pend = p + page->total_slots;
+	for (;p < pend; p++) {
+	    if (p->as.basic.flags) {
+		counts[BUILTIN_TYPE(p)]++;
+	    }
+	    else {
+		freed++;
+	    }
+	}
+	total += page->total_slots;
+    }
+
+    if (hash == Qnil) {
+        hash = rb_hash_new();
+    }
+    else if (!RHASH_EMPTY_P(hash)) {
+        st_foreach(RHASH_TBL_RAW(hash), set_zero, hash);
+    }
+    rb_hash_aset(hash, ID2SYM(rb_intern("TOTAL")), SIZET2NUM(total));
+    rb_hash_aset(hash, ID2SYM(rb_intern("FREE")), SIZET2NUM(freed));
+
+    for (i = 0; i <= T_MASK; i++) {
+        VALUE type;
+        switch (i) {
+#define COUNT_TYPE(t) case (t): type = ID2SYM(rb_intern(#t)); break;
+	    COUNT_TYPE(T_NONE);
+	    COUNT_TYPE(T_OBJECT);
+	    COUNT_TYPE(T_CLASS);
+	    COUNT_TYPE(T_MODULE);
+	    COUNT_TYPE(T_FLOAT);
+	    COUNT_TYPE(T_STRING);
+	    COUNT_TYPE(T_REGEXP);
+	    COUNT_TYPE(T_ARRAY);
+	    COUNT_TYPE(T_HASH);
+	    COUNT_TYPE(T_STRUCT);
+	    COUNT_TYPE(T_BIGNUM);
+	    COUNT_TYPE(T_FILE);
+	    COUNT_TYPE(T_DATA);
+	    COUNT_TYPE(T_MATCH);
+	    COUNT_TYPE(T_COMPLEX);
+	    COUNT_TYPE(T_RATIONAL);
+	    COUNT_TYPE(T_NIL);
+	    COUNT_TYPE(T_TRUE);
+	    COUNT_TYPE(T_FALSE);
+	    COUNT_TYPE(T_SYMBOL);
+	    COUNT_TYPE(T_FIXNUM);
+	    COUNT_TYPE(T_UNDEF);
+	    COUNT_TYPE(T_NODE);
+	    COUNT_TYPE(T_ICLASS);
+	    COUNT_TYPE(T_ZOMBIE);
+#undef COUNT_TYPE
+          default:              type = INT2NUM(i); break;
+        }
+        if (counts[i])
+            rb_hash_aset(hash, type, SIZET2NUM(counts[i]));
+    }
+
+    return hash;
+}
+
+/*
+  ------------------------ Garbage Collection ------------------------
+*/
+
+/* Sweeping */
+
+static size_t
+objspace_available_slots(rb_objspace_t *objspace)
+{
+    return heap_eden->total_slots + heap_tomb->total_slots;
+}
+
+static size_t
+objspace_live_slots(rb_objspace_t *objspace)
+{
+    return (objspace->total_allocated_objects - objspace->profile.total_freed_objects) - heap_pages_final_slots;
+}
+
+static size_t
+objspace_free_slots(rb_objspace_t *objspace)
+{
+    return objspace_available_slots(objspace) - objspace_live_slots(objspace) - heap_pages_final_slots;
+}
+
+static void
+gc_setup_mark_bits(struct heap_page *page)
+{
+#if USE_RGENGC
+    /* copy oldgen bitmap to mark bitmap */
+    memcpy(&page->mark_bits[0], &page->long_lived_bits[0], HEAP_BITMAP_SIZE);
+#else
+    /* clear mark bitmap */
+    memset(&page->mark_bits[0], 0, HEAP_BITMAP_SIZE);
+#endif
+}
+
+/* TRUE : has empty slots                                             */
+/* FALSE: no empty slots (or move to tomb heap because no live slots) */
+static inline void
+gc_page_sweep(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *sweep_page)
+{
+    int i;
+    int empty_slots = 0, freed_slots = 0, final_slots = 0;
+    RVALUE *p, *pend,*offset;
+    bits_t *bits, bitset;
+
+    gc_report(2, objspace, "page_sweep: start.\n");
+
+    sweep_page->flags.before_sweep = FALSE;
+
+    p = sweep_page->start; pend = p + sweep_page->total_slots;
+    offset = p - NUM_IN_PAGE(p);
+    bits = sweep_page->mark_bits;
+
+    /* create guard : fill 1 out-of-range */
+    bits[BITMAP_INDEX(p)] |= BITMAP_BIT(p)-1;
+    bits[BITMAP_INDEX(pend)] |= ~(BITMAP_BIT(pend) - 1);
+
+    for (i=0; i < HEAP_BITMAP_LIMIT; i++) {
+	bitset = ~bits[i];
+	if (bitset) {
+	    p = offset  + i * BITS_BITLENGTH;
+	    do {
+		if (bitset & 1) {
+		    switch (BUILTIN_TYPE(p)) {
+		      default: { /* majority case */
+			  gc_report(2, objspace, "page_sweep: free %s\n", obj_info((VALUE)p));
+#if USE_RGENGC && RGENGC_CHECK_MODE
+			  if (!is_full_marking(objspace)) {
+			      if (RVALUE_OLD_P((VALUE)p)) rb_bug("page_sweep: %s - old while minor GC.", obj_info((VALUE)p));
+			      if (rgengc_remembered(objspace, (VALUE)p)) rb_bug("page_sweep: %s - remembered.", obj_info((VALUE)p));
+			  }
+#endif
+			  if (obj_free(objspace, (VALUE)p)) {
+			      final_slots++;
+			  }
+			  else {
+			      (void)VALGRIND_MAKE_MEM_UNDEFINED((void*)p, sizeof(RVALUE));
+			      heap_page_add_freeobj(objspace, sweep_page, (VALUE)p);
+			      gc_report(3, objspace, "page_sweep: %s is added to freelist\n", obj_info((VALUE)p));
+			      freed_slots++;
+			  }
+			  break;
+		      }
+
+			/* minor cases */
+		      case T_ZOMBIE:
+			/* already counted */
+			break;
+		      case T_NONE:
+			empty_slots++; /* already freed */
+			break;
+		    }
+		}
+		p++;
+		bitset >>= 1;
+	    } while (bitset);
+	}
+    }
+
+    gc_setup_mark_bits(sweep_page);
+
+#if GC_PROFILE_MORE_DETAIL
+    if (gc_prof_enabled(objspace)) {
+	gc_profile_record *record = gc_prof_record(objspace);
+	record->removing_objects += final_slots + freed_slots;
+	record->empty_objects += empty_slots;
+    }
+#endif
+    if (0) fprintf(stderr, "gc_page_sweep(%d): total_slots: %d, freed_slots: %d, empty_slots: %d, final_slots: %d\n",
+		   (int)rb_gc_count(),
+		   (int)sweep_page->total_slots,
+		   freed_slots, empty_slots, final_slots);
+
+    heap_pages_swept_slots += sweep_page->free_slots = freed_slots + empty_slots;
+    objspace->profile.total_freed_objects += freed_slots;
+    heap_pages_final_slots += final_slots;
+    sweep_page->final_slots += final_slots;
+
+    if (heap_pages_deferred_final && !finalizing) {
+        rb_thread_t *th = GET_THREAD();
+        if (th) {
+	    gc_finalize_deferred_register();
+        }
+    }
+
+    gc_report(2, objspace, "page_sweep: end.\n");
+}
+
+/* allocate additional minimum page to work */
+static void
+gc_heap_prepare_minimum_pages(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    if (!heap->free_pages && heap_increment(objspace, heap) == FALSE) {
+	/* there is no free after page_sweep() */
+	heap_set_increment(objspace, 1);
+	if (!heap_increment(objspace, heap)) { /* can't allocate additional free objects */
+	    rb_memerror();
+	}
+    }
+}
+
+static void
+gc_stat_transition(rb_objspace_t *objspace, enum gc_stat stat)
+{
+#if RGENGC_CHECK_MODE
+    enum gc_stat prev_stat = objspace->flags.stat;
+    switch (prev_stat) {
+      case gc_stat_none: assert(stat == gc_stat_marking); break;
+      case gc_stat_marking: assert(stat == gc_stat_sweeping); break;
+      case gc_stat_sweeping: assert(stat == gc_stat_none); break;
+    }
+#endif
+    objspace->flags.stat = stat;
+}
+
+static void
+gc_sweep_start_heap(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    heap->sweep_pages = heap->pages;
+    heap->free_pages = NULL;
+#if GC_ENABLE_INCREMENTAL_MARK
+    heap->pooled_pages = NULL;
+    objspace->rincgc.pooled_slots = 0;
+#endif
+    if (heap->using_page) {
+	RVALUE **p = &heap->using_page->freelist;
+	while (*p) {
+	    p = &(*p)->as.free.next;
+	}
+	*p = heap->freelist;
+	heap->using_page = NULL;
+    }
+    heap->freelist = NULL;
+}
+
+#if defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ == 4
+__attribute__((noinline))
+#endif
+static void
+gc_sweep_start(rb_objspace_t *objspace)
+{
+    rb_heap_t *heap;
+    size_t total_limit_slot;
+
+    gc_stat_transition(objspace, gc_stat_sweeping);
+
+    /* sweep unlinked method entries */
+    if (GET_VM()->unlinked_method_entry_list) {
+	rb_sweep_method_entry(GET_VM());
+    }
+
+    /* sometimes heap_allocatable_pages is not 0 */
+    heap_pages_swept_slots = heap_allocatable_pages * HEAP_OBJ_LIMIT;
+    total_limit_slot = objspace_available_slots(objspace);
+
+    heap_pages_min_free_slots = (size_t)(total_limit_slot * GC_HEAP_FREE_SLOTS_MIN_RATIO);
+    if (heap_pages_min_free_slots < gc_params.heap_free_slots) {
+	heap_pages_min_free_slots = gc_params.heap_free_slots;
+    }
+    heap_pages_max_free_slots = (size_t)(total_limit_slot * GC_HEAP_FREE_SLOTS_MAX_RATIO);
+    if (heap_pages_max_free_slots < gc_params.heap_init_slots) {
+	heap_pages_max_free_slots = gc_params.heap_init_slots;
+    }
+    if (0) fprintf(stderr, "heap_pages_min_free_slots: %d, heap_pages_max_free_slots: %d\n",
+		   (int)heap_pages_min_free_slots, (int)heap_pages_max_free_slots);
+
+    heap = heap_eden;
+    gc_sweep_start_heap(objspace, heap);
+}
+
+static void
+gc_sweep_finish(rb_objspace_t *objspace)
+{
+    rb_heap_t *heap = heap_eden;
+
+    gc_report(1, objspace, "gc_sweep_finish: heap->total_slots: %d, heap->swept_slots: %d, min_free_slots: %d\n",
+		  (int)heap->total_slots, (int)heap_pages_swept_slots, (int)heap_pages_min_free_slots);
+
+    gc_prof_set_heap_info(objspace);
+
+    heap_pages_free_unused_pages(objspace);
+
+    /* if heap_pages has unused pages, then assign them to increment */
+    if (heap_allocatable_pages < heap_tomb->page_length) {
+	heap_allocatable_pages = heap_tomb->page_length;
+    }
+
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_GC_END_SWEEP, 0);
+    gc_stat_transition(objspace, gc_stat_none);
+
+#if RGENGC_CHECK_MODE >= 2
+    gc_verify_internal_consistency(Qnil);
+#endif
+}
+
+static int
+gc_sweep_step(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    struct heap_page *sweep_page = heap->sweep_pages, *next;
+    int unlink_limit = 3;
+#if GC_ENABLE_INCREMENTAL_MARK
+    int need_pool = will_be_incremental_marking(objspace) ? TRUE : FALSE;
+
+    gc_report(2, objspace, "gc_sweep_step (need_pool: %d)\n", need_pool);
+#else
+    gc_report(2, objspace, "gc_sweep_step\n");
+#endif
+
+    if (sweep_page == NULL) return FALSE;
+
+#if GC_ENABLE_LAZY_SWEEP
+    gc_prof_sweep_timer_start(objspace);
+#endif
+
+    while (sweep_page) {
+	heap->sweep_pages = next = sweep_page->next;
+	gc_page_sweep(objspace, heap, sweep_page);
+
+	if (sweep_page->final_slots + sweep_page->free_slots == sweep_page->total_slots &&
+	    unlink_limit > 0) {
+	    unlink_limit--;
+	    /* there are no living objects -> move this page to tomb heap */
+	    heap_unlink_page(objspace, heap, sweep_page);
+	    heap_add_page(objspace, heap_tomb, sweep_page);
+	}
+	else if (sweep_page->free_slots > 0) {
+#if GC_ENABLE_INCREMENTAL_MARK
+	    if (need_pool) {
+		if (heap_add_poolpage(objspace, heap, sweep_page)) {
+		    need_pool = FALSE;
+		}
+	    }
+	    else {
+		heap_add_freepage(objspace, heap, sweep_page);
+		break;
+	    }
+#else
+	    heap_add_freepage(objspace, heap, sweep_page);
+	    break;
+#endif
+	}
+	else {
+	    sweep_page->free_next = NULL;
+	}
+
+	sweep_page = next;
+    }
+
+    if (heap->sweep_pages == NULL) {
+	gc_sweep_finish(objspace);
+    }
+
+#if GC_ENABLE_LAZY_SWEEP
+    gc_prof_sweep_timer_stop(objspace);
+#endif
+
+    return heap->free_pages != NULL;
+}
+
+static void
+gc_sweep_rest(rb_objspace_t *objspace)
+{
+    rb_heap_t *heap = heap_eden; /* lazy sweep only for eden */
+
+    while (has_sweeping_pages(heap)) {
+	gc_sweep_step(objspace, heap);
+    }
+}
+
+#if GC_ENABLE_LAZY_SWEEP
+static void
+gc_sweep_continue(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    if (RGENGC_CHECK_MODE) assert(dont_gc == FALSE);
+
+    gc_enter(objspace, "sweep_continue");
+#if USE_RGENGC
+    if (objspace->rgengc.need_major_gc == GPR_FLAG_NONE && heap_increment(objspace, heap)) {
+	gc_report(3, objspace, "gc_sweep_continue: success heap_increment().\n");
+    }
+#endif
+    gc_sweep_step(objspace, heap);
+    gc_exit(objspace, "sweep_continue");
+}
+#endif
+
+static void
+gc_sweep(rb_objspace_t *objspace)
+{
+    const unsigned int immediate_sweep = objspace->flags.immediate_sweep;
+
+    gc_report(1, objspace, "gc_sweep: immediate: %d\n", immediate_sweep);
+
+    if (immediate_sweep) {
+#if !GC_ENABLE_LAZY_SWEEP
+	gc_prof_sweep_timer_start(objspace);
+#endif
+	gc_sweep_start(objspace);
+	gc_sweep_rest(objspace);
+#if !GC_ENABLE_LAZY_SWEEP
+	gc_prof_sweep_timer_stop(objspace);
+#endif
+    }
+    else {
+	struct heap_page *page;
+	gc_sweep_start(objspace);
+	page = heap_eden->sweep_pages;
+	while (page) {
+	    page->flags.before_sweep = TRUE;
+	    page = page->next;
+	}
+	gc_sweep_step(objspace, heap_eden);
+    }
+
+    gc_heap_prepare_minimum_pages(objspace, heap_eden);
+}
+
+/* Marking - Marking stack */
+
+static stack_chunk_t *
+stack_chunk_alloc(void)
+{
+    stack_chunk_t *res;
+
+    res = malloc(sizeof(stack_chunk_t));
+    if (!res)
+        rb_memerror();
+
+    return res;
+}
+
+static inline int
+is_mark_stack_empty(mark_stack_t *stack)
+{
+    return stack->chunk == NULL;
+}
+
+static size_t
+mark_stack_size(mark_stack_t *stack)
+{
+    size_t size = stack->index;
+    stack_chunk_t *chunk = stack->chunk ? stack->chunk->next : NULL;
+
+    while (chunk) {
+	size += stack->limit;
+	chunk = chunk->next;
+    }
+    return size;
+}
+
+static void
+add_stack_chunk_cache(mark_stack_t *stack, stack_chunk_t *chunk)
+{
+    chunk->next = stack->cache;
+    stack->cache = chunk;
+    stack->cache_size++;
+}
+
+static void
+shrink_stack_chunk_cache(mark_stack_t *stack)
+{
+    stack_chunk_t *chunk;
+
+    if (stack->unused_cache_size > (stack->cache_size/2)) {
+        chunk = stack->cache;
+        stack->cache = stack->cache->next;
+        stack->cache_size--;
+        free(chunk);
+    }
+    stack->unused_cache_size = stack->cache_size;
+}
+
+static void
+push_mark_stack_chunk(mark_stack_t *stack)
+{
+    stack_chunk_t *next;
+
+    if (RGENGC_CHECK_MODE) assert(stack->index == stack->limit);
+
+    if (stack->cache_size > 0) {
+        next = stack->cache;
+        stack->cache = stack->cache->next;
+        stack->cache_size--;
+        if (stack->unused_cache_size > stack->cache_size)
+            stack->unused_cache_size = stack->cache_size;
+    }
+    else {
+        next = stack_chunk_alloc();
+    }
+    next->next = stack->chunk;
+    stack->chunk = next;
+    stack->index = 0;
+}
+
+static void
+pop_mark_stack_chunk(mark_stack_t *stack)
+{
+    stack_chunk_t *prev;
+
+    prev = stack->chunk->next;
+    if (RGENGC_CHECK_MODE) assert(stack->index == 0);
+    add_stack_chunk_cache(stack, stack->chunk);
+    stack->chunk = prev;
+    stack->index = stack->limit;
+}
+
+#if (defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE) || (RGENGC_CHECK_MODE >= 4)
+static void
+free_stack_chunks(mark_stack_t *stack)
+{
+    stack_chunk_t *chunk = stack->chunk;
+    stack_chunk_t *next = NULL;
+
+    while (chunk != NULL) {
+        next = chunk->next;
+        free(chunk);
+        chunk = next;
+    }
+}
+#endif
+
+static void
+push_mark_stack(mark_stack_t *stack, VALUE data)
+{
+    if (stack->index == stack->limit) {
+        push_mark_stack_chunk(stack);
+    }
+    stack->chunk->data[stack->index++] = data;
+}
+
+static int
+pop_mark_stack(mark_stack_t *stack, VALUE *data)
+{
+    if (is_mark_stack_empty(stack)) {
+        return FALSE;
+    }
+    if (stack->index == 1) {
+        *data = stack->chunk->data[--stack->index];
+        pop_mark_stack_chunk(stack);
+    }
+    else {
+	*data = stack->chunk->data[--stack->index];
+    }
+    return TRUE;
+}
+
+#if GC_ENABLE_INCREMENTAL_MARK
+static int
+invalidate_mark_stack_chunk(stack_chunk_t *chunk, int limit, VALUE obj)
+{
+    int i;
+    for (i=0; i<limit; i++) {
+	if (chunk->data[i] == obj) {
+	    chunk->data[i] = Qundef;
+	    return TRUE;
+	}
+    }
+    return FALSE;
+}
+
+static void
+invalidate_mark_stack(mark_stack_t *stack, VALUE obj)
+{
+    stack_chunk_t *chunk = stack->chunk;
+    int limit = stack->index;
+
+    while (chunk) {
+	if (invalidate_mark_stack_chunk(chunk, limit, obj)) return;
+	chunk = chunk->next;
+	limit = stack->limit;
+    }
+    rb_bug("invalid_mark_stack: unreachable");
+}
+#endif
+
+static void
+init_mark_stack(mark_stack_t *stack)
+{
+    int i;
+
+    MEMZERO(stack, mark_stack_t, 1);
+    stack->index = stack->limit = STACK_CHUNK_SIZE;
+    stack->cache_size = 0;
+
+    for (i=0; i < 4; i++) {
+        add_stack_chunk_cache(stack, stack_chunk_alloc());
+    }
+    stack->unused_cache_size = stack->cache_size;
+}
+
+/* Marking */
+
+#ifdef __ia64
+#define SET_STACK_END (SET_MACHINE_STACK_END(&th->machine.stack_end), th->machine.register_stack_end = rb_ia64_bsp())
+#else
+#define SET_STACK_END SET_MACHINE_STACK_END(&th->machine.stack_end)
+#endif
+
+#define STACK_START (th->machine.stack_start)
+#define STACK_END (th->machine.stack_end)
+#define STACK_LEVEL_MAX (th->machine.stack_maxsize/sizeof(VALUE))
+
+#if STACK_GROW_DIRECTION < 0
+# define STACK_LENGTH  (size_t)(STACK_START - STACK_END)
+#elif STACK_GROW_DIRECTION > 0
+# define STACK_LENGTH  (size_t)(STACK_END - STACK_START + 1)
+#else
+# define STACK_LENGTH  ((STACK_END < STACK_START) ? (size_t)(STACK_START - STACK_END) \
+			: (size_t)(STACK_END - STACK_START + 1))
+#endif
+#if !STACK_GROW_DIRECTION
+int ruby_stack_grow_direction;
+int
+ruby_get_stack_grow_direction(volatile VALUE *addr)
+{
+    VALUE *end;
+    SET_MACHINE_STACK_END(&end);
+
+    if (end > addr) return ruby_stack_grow_direction = 1;
+    return ruby_stack_grow_direction = -1;
+}
+#endif
+
+size_t
+ruby_stack_length(VALUE **p)
+{
+    rb_thread_t *th = GET_THREAD();
+    SET_STACK_END;
+    if (p) *p = STACK_UPPER(STACK_END, STACK_START, STACK_END);
+    return STACK_LENGTH;
+}
+
+#if !(defined(POSIX_SIGNAL) && defined(SIGSEGV) && defined(HAVE_SIGALTSTACK))
+static int
+stack_check(int water_mark)
+{
+    int ret;
+    rb_thread_t *th = GET_THREAD();
+    SET_STACK_END;
+    ret = STACK_LENGTH > STACK_LEVEL_MAX - water_mark;
+#ifdef __ia64
+    if (!ret) {
+        ret = (VALUE*)rb_ia64_bsp() - th->machine.register_stack_start >
+              th->machine.register_stack_maxsize/sizeof(VALUE) - water_mark;
+    }
+#endif
+    return ret;
+}
+#endif
+
+#define STACKFRAME_FOR_CALL_CFUNC 512
+
+int
+ruby_stack_check(void)
+{
+#if defined(POSIX_SIGNAL) && defined(SIGSEGV) && defined(HAVE_SIGALTSTACK)
+    return 0;
+#else
+    return stack_check(STACKFRAME_FOR_CALL_CFUNC);
+#endif
+}
+
+ATTRIBUTE_NO_ADDRESS_SAFETY_ANALYSIS
+static void
+mark_locations_array(rb_objspace_t *objspace, register const VALUE *x, register long n)
+{
+    VALUE v;
+    while (n--) {
+        v = *x;
+	gc_mark_maybe(objspace, v);
+	x++;
+    }
+}
+
+static void
+gc_mark_locations(rb_objspace_t *objspace, const VALUE *start, const VALUE *end)
+{
+    long n;
+
+    if (end <= start) return;
+    n = end - start;
+    mark_locations_array(objspace, start, n);
+}
+
+void
+rb_gc_mark_locations(const VALUE *start, const VALUE *end)
+{
+    gc_mark_locations(&rb_objspace, start, end);
+}
+
+void
+rb_gc_mark_values(long n, const VALUE *values)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    long i;
+
+    for (i=0; i<n; i++) {
+	gc_mark(objspace, values[i]);
+    }
+}
+
+#define rb_gc_mark_locations(start, end) gc_mark_locations(objspace, (start), (end))
+
+struct mark_tbl_arg {
+    rb_objspace_t *objspace;
+};
+
+static int
+mark_entry(st_data_t key, st_data_t value, st_data_t data)
+{
+    struct mark_tbl_arg *arg = (void*)data;
+    gc_mark(arg->objspace, (VALUE)value);
+    return ST_CONTINUE;
+}
+
+static void
+mark_tbl(rb_objspace_t *objspace, st_table *tbl)
+{
+    struct mark_tbl_arg arg;
+    if (!tbl || tbl->num_entries == 0) return;
+    arg.objspace = objspace;
+    st_foreach(tbl, mark_entry, (st_data_t)&arg);
+}
+
+static int
+mark_key(st_data_t key, st_data_t value, st_data_t data)
+{
+    struct mark_tbl_arg *arg = (void*)data;
+    gc_mark(arg->objspace, (VALUE)key);
+    return ST_CONTINUE;
+}
+
+static void
+mark_set(rb_objspace_t *objspace, st_table *tbl)
+{
+    struct mark_tbl_arg arg;
+    if (!tbl) return;
+    arg.objspace = objspace;
+    st_foreach(tbl, mark_key, (st_data_t)&arg);
+}
+
+void
+rb_mark_set(st_table *tbl)
+{
+    mark_set(&rb_objspace, tbl);
+}
+
+static int
+mark_keyvalue(st_data_t key, st_data_t value, st_data_t data)
+{
+    struct mark_tbl_arg *arg = (void*)data;
+    gc_mark(arg->objspace, (VALUE)key);
+    gc_mark(arg->objspace, (VALUE)value);
+    return ST_CONTINUE;
+}
+
+static void
+mark_hash(rb_objspace_t *objspace, st_table *tbl)
+{
+    struct mark_tbl_arg arg;
+    if (!tbl) return;
+    arg.objspace = objspace;
+    st_foreach(tbl, mark_keyvalue, (st_data_t)&arg);
+}
+
+void
+rb_mark_hash(st_table *tbl)
+{
+    mark_hash(&rb_objspace, tbl);
+}
+
+static void
+mark_method_entry(rb_objspace_t *objspace, const rb_method_entry_t *me)
+{
+    const rb_method_definition_t *def = me->def;
+
+    gc_mark(objspace, me->klass);
+  again:
+    if (!def) return;
+    switch (def->type) {
+      case VM_METHOD_TYPE_ISEQ:
+	gc_mark(objspace, def->body.iseq->self);
+	break;
+      case VM_METHOD_TYPE_BMETHOD:
+	gc_mark(objspace, def->body.proc);
+	break;
+      case VM_METHOD_TYPE_ATTRSET:
+      case VM_METHOD_TYPE_IVAR:
+	gc_mark(objspace, def->body.attr.location);
+	break;
+      case VM_METHOD_TYPE_REFINED:
+	if (def->body.orig_me) {
+	    def = def->body.orig_me->def;
+	    goto again;
+	}
+	break;
+      default:
+	break; /* ignore */
+    }
+}
+
+void
+rb_mark_method_entry(const rb_method_entry_t *me)
+{
+    mark_method_entry(&rb_objspace, me);
+}
+
+static int
+mark_method_entry_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    const rb_method_entry_t *me = (const rb_method_entry_t *)value;
+    struct mark_tbl_arg *arg = (void*)data;
+    mark_method_entry(arg->objspace, me);
+    return ST_CONTINUE;
+}
+
+static void
+mark_m_tbl_wrapper(rb_objspace_t *objspace, struct method_table_wrapper *wrapper)
+{
+    struct mark_tbl_arg arg;
+    if (!wrapper || !wrapper->tbl) return;
+    if (LIKELY(objspace->mark_func_data == 0) && !is_incremental_marking(objspace)) {
+	/* prevent multiple marking during same GC cycle,
+	 * since m_tbl is shared between several T_ICLASS */
+	size_t serial = rb_gc_count();
+	if (wrapper->serial == serial) return;
+	wrapper->serial = serial;
+    }
+    arg.objspace = objspace;
+    st_foreach(wrapper->tbl, mark_method_entry_i, (st_data_t)&arg);
+}
+
+static int
+mark_const_entry_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    const rb_const_entry_t *ce = (const rb_const_entry_t *)value;
+    struct mark_tbl_arg *arg = (void*)data;
+    gc_mark(arg->objspace, ce->value);
+    gc_mark(arg->objspace, ce->file);
+    return ST_CONTINUE;
+}
+
+static void
+mark_const_tbl(rb_objspace_t *objspace, st_table *tbl)
+{
+    struct mark_tbl_arg arg;
+    if (!tbl) return;
+    arg.objspace = objspace;
+    st_foreach(tbl, mark_const_entry_i, (st_data_t)&arg);
+}
+
+#if STACK_GROW_DIRECTION < 0
+#define GET_STACK_BOUNDS(start, end, appendix) ((start) = STACK_END, (end) = STACK_START)
+#elif STACK_GROW_DIRECTION > 0
+#define GET_STACK_BOUNDS(start, end, appendix) ((start) = STACK_START, (end) = STACK_END+(appendix))
+#else
+#define GET_STACK_BOUNDS(start, end, appendix) \
+    ((STACK_END < STACK_START) ? \
+     ((start) = STACK_END, (end) = STACK_START) : ((start) = STACK_START, (end) = STACK_END+(appendix)))
+#endif
+
+static void
+mark_current_machine_context(rb_objspace_t *objspace, rb_thread_t *th)
+{
+    union {
+	rb_jmp_buf j;
+	VALUE v[sizeof(rb_jmp_buf) / sizeof(VALUE)];
+    } save_regs_gc_mark;
+    VALUE *stack_start, *stack_end;
+
+    FLUSH_REGISTER_WINDOWS;
+    /* This assumes that all registers are saved into the jmp_buf (and stack) */
+    rb_setjmp(save_regs_gc_mark.j);
+
+    /* SET_STACK_END must be called in this function because
+     * the stack frame of this function may contain
+     * callee save registers and they should be marked. */
+    SET_STACK_END;
+    GET_STACK_BOUNDS(stack_start, stack_end, 1);
+
+    mark_locations_array(objspace, save_regs_gc_mark.v, numberof(save_regs_gc_mark.v));
+
+    rb_gc_mark_locations(stack_start, stack_end);
+#ifdef __ia64
+    rb_gc_mark_locations(th->machine.register_stack_start, th->machine.register_stack_end);
+#endif
+#if defined(__mc68000__)
+    rb_gc_mark_locations((VALUE*)((char*)stack_start + 2),
+			 (VALUE*)((char*)stack_end - 2));
+#endif
+}
+
+void
+rb_gc_mark_machine_stack(rb_thread_t *th)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE *stack_start, *stack_end;
+
+    GET_STACK_BOUNDS(stack_start, stack_end, 0);
+    rb_gc_mark_locations(stack_start, stack_end);
+#ifdef __ia64
+    rb_gc_mark_locations(th->machine.register_stack_start, th->machine.register_stack_end);
+#endif
+#if defined(__mc68000__)
+    rb_gc_mark_locations((VALUE*)((char*)stack_start + 2),
+			 (VALUE*)((char*)stack_end - 2));
+#endif
+}
+
+void
+rb_mark_tbl(st_table *tbl)
+{
+    mark_tbl(&rb_objspace, tbl);
+}
+
+static void
+gc_mark_maybe(rb_objspace_t *objspace, VALUE obj)
+{
+    (void)VALGRIND_MAKE_MEM_DEFINED(&obj, sizeof(obj));
+    if (is_pointer_to_heap(objspace, (void *)obj)) {
+	int type = BUILTIN_TYPE(obj);
+	if (type != T_ZOMBIE && type != T_NONE) {
+	    gc_mark_ptr(objspace, obj);
+	}
+    }
+}
+
+void
+rb_gc_mark_maybe(VALUE obj)
+{
+    gc_mark_maybe(&rb_objspace, obj);
+}
+
+static inline int
+gc_mark_set(rb_objspace_t *objspace, VALUE obj)
+{
+    if (RVALUE_MARKED(obj)) return 0;
+    MARK_IN_BITMAP(GET_HEAP_MARK_BITS(obj), obj);
+    return 1;
+}
+
+#if USE_RGENGC
+static int
+gc_remember_unprotected(rb_objspace_t *objspace, VALUE obj)
+{
+    struct heap_page *page = GET_HEAP_PAGE(obj);
+    bits_t *bits = &page->long_lived_bits[0];
+
+    if (!MARKED_IN_BITMAP(bits, obj)) {
+	page->flags.has_long_lived_shady_objects = TRUE;
+	MARK_IN_BITMAP(bits, obj);
+	objspace->rgengc.remembered_wb_unprotected_objects++;
+
+#if RGENGC_PROFILE > 0
+	objspace->profile.total_remembered_shady_object_count++;
+#if RGENGC_PROFILE >= 2
+	objspace->profile.remembered_shady_object_count_types[BUILTIN_TYPE(obj)]++;
+#endif
+#endif
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+#endif
+
+static void
+rgengc_check_relation(rb_objspace_t *objspace, VALUE obj)
+{
+#if USE_RGENGC
+    const VALUE old_parent = objspace->rgengc.parent_object;
+
+    if (old_parent) { /* parent object is old */
+	if (RVALUE_WB_UNPROTECTED(obj)) {
+	    if (gc_remember_unprotected(objspace, obj)) {
+		gc_report(2, objspace, "relation: (O->S) %s -> %s\n", obj_info(old_parent), obj_info(obj));
+	    }
+	}
+	else {
+	    if (!RVALUE_OLD_P(obj)) {
+		if (RVALUE_MARKED(obj)) {
+		    /* An object pointed from an OLD object should be OLD. */
+		    gc_report(2, objspace, "relation: (O->unmarked Y) %s -> %s\n", obj_info(old_parent), obj_info(obj));
+		    RVALUE_AGE_SET_OLD(objspace, obj);
+		    if (is_incremental_marking(objspace)) {
+			if (!RVALUE_MARKING(obj)) {
+			    gc_grey(objspace, obj);
+			}
+		    }
+		    else {
+			rgengc_remember(objspace, obj);
+		    }
+		}
+		else {
+		    gc_report(2, objspace, "relation: (O->Y) %s -> %s\n", obj_info(old_parent), obj_info(obj));
+		    RVALUE_AGE_SET_CANDIDATE(objspace, obj);
+		}
+	    }
+	}
+    }
+
+    if (RGENGC_CHECK_MODE) assert(old_parent == objspace->rgengc.parent_object);
+#endif
+}
+
+static void
+gc_grey(rb_objspace_t *objspace, VALUE obj)
+{
+#if RGENGC_CHECK_MODE
+    if (RVALUE_MARKED(obj) == FALSE) rb_bug("gc_grey: %s is not marked.", obj_info(obj));
+    if (RVALUE_MARKING(obj) == TRUE) rb_bug("gc_grey: %s is marking/remembered.", obj_info(obj));
+#endif
+
+#if GC_ENABLE_INCREMENTAL_MARK
+    if (is_incremental_marking(objspace)) {
+	MARK_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), obj);
+    }
+#endif
+
+    push_mark_stack(&objspace->mark_stack, obj);
+}
+
+static void
+gc_aging(rb_objspace_t *objspace, VALUE obj)
+{
+#if USE_RGENGC
+    struct heap_page *page = GET_HEAP_PAGE(obj);
+
+#if RGENGC_CHECK_MODE
+    assert(RVALUE_MARKING(obj) == FALSE);
+#endif
+
+    check_rvalue_consistency(obj);
+
+    if (RVALUE_PAGE_WB_UNPROTECTED(page, obj) == 0) {
+	if (!RVALUE_OLD_P(obj)) {
+	    gc_report(3, objspace, "gc_aging: YOUNG: %s\n", obj_info(obj));
+	    RVALUE_AGE_INC(objspace, obj);
+	}
+	else if (is_full_marking(objspace)) {
+	    if (RGENGC_CHECK_MODE) assert(RVALUE_PAGE_LONG_LIVED(page, obj) == FALSE);
+	    MARK_IN_BITMAP(page->long_lived_bits, obj);
+	    objspace->rgengc.old_objects++;
+	}
+    }
+    check_rvalue_consistency(obj);
+#endif /* USE_RGENGC */
+
+    objspace->marked_slots++;
+}
+
+static void
+gc_mark_ptr(rb_objspace_t *objspace, VALUE obj)
+{
+    if (LIKELY(objspace->mark_func_data == NULL)) {
+	rgengc_check_relation(objspace, obj);
+	if (!gc_mark_set(objspace, obj)) return; /* already marked */
+	gc_aging(objspace, obj);
+	gc_grey(objspace, obj);
+    }
+    else {
+	objspace->mark_func_data->mark_func(obj, objspace->mark_func_data->data);
+    }
+}
+
+static void
+gc_mark(rb_objspace_t *objspace, VALUE obj)
+{
+    if (!is_markable_object(objspace, obj)) return;
+    gc_mark_ptr(objspace, obj);
+}
+
+void
+rb_gc_mark(VALUE ptr)
+{
+    gc_mark(&rb_objspace, ptr);
+}
+
+/* CAUTION: THIS FUNCTION ENABLE *ONLY BEFORE* SWEEPING.
+ * This function is only for GC_END_MARK timing.
+ */
+
+int
+rb_objspace_marked_object_p(VALUE obj)
+{
+    return RVALUE_MARKED(obj) ? TRUE : FALSE;
+}
+
+static inline void
+gc_mark_set_parent(rb_objspace_t *objspace, VALUE obj)
+{
+#if USE_RGENGC
+    if (RVALUE_OLD_P(obj)) {
+	objspace->rgengc.parent_object = obj;
+    }
+    else {
+	objspace->rgengc.parent_object = Qfalse;
+    }
+#endif
+}
+
+static void
+gc_mark_children(rb_objspace_t *objspace, VALUE obj)
+{
+    register RVALUE *any = RANY(obj);
+    gc_mark_set_parent(objspace, obj);
+
+    if (FL_TEST(obj, FL_EXIVAR)) {
+	rb_mark_generic_ivar(obj);
+    }
+
+    switch (BUILTIN_TYPE(obj)) {
+      case T_NIL:
+      case T_FIXNUM:
+	rb_bug("rb_gc_mark() called for broken object");
+	break;
+
+      case T_NODE:
+	obj = rb_gc_mark_node(&any->as.node);
+	if (obj) gc_mark(objspace, obj);
+	return;			/* no need to mark class. */
+    }
+
+    gc_mark(objspace, any->as.basic.klass);
+
+    switch (BUILTIN_TYPE(obj)) {
+      case T_ICLASS:
+      case T_CLASS:
+      case T_MODULE:
+	mark_m_tbl_wrapper(objspace, RCLASS_M_TBL_WRAPPER(obj));
+	if (!RCLASS_EXT(obj)) break;
+	mark_tbl(objspace, RCLASS_IV_TBL(obj));
+	mark_const_tbl(objspace, RCLASS_CONST_TBL(obj));
+	gc_mark(objspace, RCLASS_SUPER((VALUE)obj));
+	break;
+
+      case T_ARRAY:
+	if (FL_TEST(obj, ELTS_SHARED)) {
+	    gc_mark(objspace, any->as.array.as.heap.aux.shared);
+	}
+	else {
+	    long i, len = RARRAY_LEN(obj);
+	    const VALUE *ptr = RARRAY_CONST_PTR(obj);
+	    for (i=0; i < len; i++) {
+		gc_mark(objspace, *ptr++);
+	    }
+	}
+	break;
+
+      case T_HASH:
+	mark_hash(objspace, any->as.hash.ntbl);
+	gc_mark(objspace, any->as.hash.ifnone);
+	break;
+
+      case T_STRING:
+	if (STR_SHARED_P(obj)) {
+	    gc_mark(objspace, any->as.string.as.heap.aux.shared);
+	}
+	break;
+
+      case T_DATA:
+	if (RTYPEDDATA_P(obj)) {
+	    RUBY_DATA_FUNC mark_func = any->as.typeddata.type->function.dmark;
+	    if (mark_func) (*mark_func)(DATA_PTR(obj));
+	}
+	else {
+	    if (any->as.data.dmark) (*any->as.data.dmark)(DATA_PTR(obj));
+	}
+	break;
+
+      case T_OBJECT:
+        {
+            long i, len = ROBJECT_NUMIV(obj);
+	    VALUE *ptr = ROBJECT_IVPTR(obj);
+            for (i  = 0; i < len; i++) {
+		gc_mark(objspace, *ptr++);
+            }
+        }
+	break;
+
+      case T_FILE:
+        if (any->as.file.fptr) {
+            gc_mark(objspace, any->as.file.fptr->pathv);
+            gc_mark(objspace, any->as.file.fptr->tied_io_for_writing);
+            gc_mark(objspace, any->as.file.fptr->writeconv_asciicompat);
+            gc_mark(objspace, any->as.file.fptr->writeconv_pre_ecopts);
+            gc_mark(objspace, any->as.file.fptr->encs.ecopts);
+            gc_mark(objspace, any->as.file.fptr->write_lock);
+        }
+        break;
+
+      case T_REGEXP:
+        gc_mark(objspace, any->as.regexp.src);
+	break;
+
+      case T_FLOAT:
+      case T_BIGNUM:
+      case T_SYMBOL:
+	break;
+
+      case T_MATCH:
+	gc_mark(objspace, any->as.match.regexp);
+	if (any->as.match.str) {
+	    gc_mark(objspace, any->as.match.str);
+	}
+	break;
+
+      case T_RATIONAL:
+	gc_mark(objspace, any->as.rational.num);
+	gc_mark(objspace, any->as.rational.den);
+	break;
+
+      case T_COMPLEX:
+	gc_mark(objspace, any->as.complex.real);
+	gc_mark(objspace, any->as.complex.imag);
+	break;
+
+      case T_STRUCT:
+	{
+	    long len = RSTRUCT_LEN(obj);
+	    const VALUE *ptr = RSTRUCT_CONST_PTR(obj);
+
+	    while (len--) {
+		gc_mark(objspace, *ptr++);
+	    }
+	}
+	break;
+
+      default:
+#if GC_DEBUG
+	rb_gcdebug_print_obj_condition((VALUE)obj);
+#endif
+	if (BUILTIN_TYPE(obj) == T_NONE)   rb_bug("rb_gc_mark(): %p is T_NONE", (void *)obj);
+	if (BUILTIN_TYPE(obj) == T_ZOMBIE) rb_bug("rb_gc_mark(): %p is T_ZOMBIE", (void *)obj);
+	rb_bug("rb_gc_mark(): unknown data type 0x%x(%p) %s",
+	       BUILTIN_TYPE(obj), any,
+	       is_pointer_to_heap(objspace, any) ? "corrupted object" : "non object");
+    }
+}
+
+/**
+ * incremental: 0 -> not incremental (do all)
+ * incremental: n -> mark at most `n' objects
+ */
+static inline int
+gc_mark_stacked_objects(rb_objspace_t *objspace, int incremental, size_t count)
+{
+    mark_stack_t *mstack = &objspace->mark_stack;
+    VALUE obj;
+#if GC_ENABLE_INCREMENTAL_MARK
+    size_t marked_slots_at_the_beggining = objspace->marked_slots;
+    size_t popped_count = 0;
+#endif
+
+    while (pop_mark_stack(mstack, &obj)) {
+	if (obj == Qundef) continue; /* skip */
+
+	if (RGENGC_CHECK_MODE && !RVALUE_MARKED(obj)) {
+	    rb_bug("gc_mark_stacked_objects: %s is not marked.", obj_info(obj));
+	}
+        gc_mark_children(objspace, obj);
+
+#if GC_ENABLE_INCREMENTAL_MARK
+	if (incremental) {
+	    if (RGENGC_CHECK_MODE && !RVALUE_MARKING(obj)) {
+		rb_bug("gc_mark_stacked_objects: incremental, but marking bit is 0");
+	    }
+	    CLEAR_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), obj);
+	    popped_count++;
+
+	    if (popped_count + (objspace->marked_slots - marked_slots_at_the_beggining) > count) {
+		break;
+	    }
+	}
+	else {
+	    /* just ignore marking bits */
+	}
+#endif
+    }
+
+    if (RGENGC_CHECK_MODE >= 3) {
+	gc_verify_internal_consistency(Qnil);
+    }
+
+    if (is_mark_stack_empty(mstack)) {
+	shrink_stack_chunk_cache(mstack);
+	return TRUE;
+    }
+    else {
+	return FALSE;
+    }
+}
+
+static int
+gc_mark_stacked_objects_incremental(rb_objspace_t *objspace, size_t count)
+{
+    return gc_mark_stacked_objects(objspace, TRUE, count);
+}
+
+static int
+gc_mark_stacked_objects_all(rb_objspace_t *objspace)
+{
+    return gc_mark_stacked_objects(objspace, FALSE, 0);
+}
+
+#if PRINT_ROOT_TICKS
+#define MAX_TICKS 0x100
+static tick_t mark_ticks[MAX_TICKS];
+static const char *mark_ticks_categories[MAX_TICKS];
+
+static void
+show_mark_ticks(void)
+{
+    int i;
+    fprintf(stderr, "mark ticks result:\n");
+    for (i=0; i<MAX_TICKS; i++) {
+	const char *category = mark_ticks_categories[i];
+	if (category) {
+	    fprintf(stderr, "%s\t%8lu\n", category, (unsigned long)mark_ticks[i]);
+	}
+	else {
+	    break;
+	}
+    }
+}
+
+#endif /* PRITNT_ROOT_TICKS */
+
+static void
+gc_mark_roots(rb_objspace_t *objspace, const char **categoryp)
+{
+    struct gc_list *list;
+    rb_thread_t *th = GET_THREAD();
+    if (categoryp) *categoryp = "xxx";
+
+#if USE_RGENGC
+    objspace->rgengc.parent_object = Qfalse;
+#endif
+
+#if PRINT_ROOT_TICKS
+    tick_t start_tick = tick();
+    int tick_count = 0;
+    const char *prev_category = 0;
+
+    if (mark_ticks_categories[0] == 0) {
+	atexit(show_mark_ticks);
+    }
+#endif
+
+#if PRINT_ROOT_TICKS
+#define MARK_CHECKPOINT_PRINT_TICK(category) do { \
+    if (prev_category) { \
+	tick_t t = tick(); \
+	mark_ticks[tick_count] = t - start_tick; \
+	mark_ticks_categories[tick_count] = prev_category; \
+	tick_count++; \
+    } \
+    prev_category = category; \
+    start_tick = tick(); \
+} while (0)
+#else /* PRITNT_ROOT_TICKS */
+#define MARK_CHECKPOINT_PRINT_TICK(category)
+#endif
+
+#define MARK_CHECKPOINT(category) do { \
+    if (categoryp) *categoryp = category; \
+    MARK_CHECKPOINT_PRINT_TICK(category); \
+} while (0)
+
+    MARK_CHECKPOINT("vm");
+    SET_STACK_END;
+    rb_vm_mark(th->vm);
+    if (th->vm->self) gc_mark_set(objspace, th->vm->self);
+
+    MARK_CHECKPOINT("finalizers");
+    mark_tbl(objspace, finalizer_table);
+
+    MARK_CHECKPOINT("machine_context");
+    mark_current_machine_context(objspace, th);
+
+    MARK_CHECKPOINT("encodings");
+    rb_gc_mark_encodings();
+
+    /* mark protected global variables */
+    MARK_CHECKPOINT("global_list");
+    for (list = global_list; list; list = list->next) {
+	rb_gc_mark_maybe(*list->varptr);
+    }
+
+    MARK_CHECKPOINT("end_proc");
+    rb_mark_end_proc();
+
+    MARK_CHECKPOINT("global_tbl");
+    rb_gc_mark_global_tbl();
+
+    /* mark generic instance variables for special constants */
+    MARK_CHECKPOINT("generic_ivars");
+    rb_mark_generic_ivar_tbl();
+
+    MARK_CHECKPOINT("live_method_entries");
+    rb_gc_mark_unlinked_live_method_entries(th->vm);
+
+    MARK_CHECKPOINT("finish");
+#undef MARK_CHECKPOINT
+}
+
+#if RGENGC_CHECK_MODE >= 4
+
+#define MAKE_ROOTSIG(obj) (((VALUE)(obj) << 1) | 0x01)
+#define IS_ROOTSIG(obj)   ((VALUE)(obj) & 0x01)
+#define GET_ROOTSIG(obj)  ((const char *)((VALUE)(obj) >> 1))
+
+struct reflist {
+    VALUE *list;
+    int pos;
+    int size;
+};
+
+static struct reflist *
+reflist_create(VALUE obj)
+{
+    struct reflist *refs = xmalloc(sizeof(struct reflist));
+    refs->size = 1;
+    refs->list = ALLOC_N(VALUE, refs->size);
+    refs->list[0] = obj;
+    refs->pos = 1;
+    return refs;
+}
+
+static void
+reflist_destruct(struct reflist *refs)
+{
+    xfree(refs->list);
+    xfree(refs);
+}
+
+static void
+reflist_add(struct reflist *refs, VALUE obj)
+{
+    if (refs->pos == refs->size) {
+	refs->size *= 2;
+	SIZED_REALLOC_N(refs->list, VALUE, refs->size, refs->size/2);
+    }
+
+    refs->list[refs->pos++] = obj;
+}
+
+static void
+reflist_dump(struct reflist *refs)
+{
+    int i;
+    for (i=0; i<refs->pos; i++) {
+	VALUE obj = refs->list[i];
+	if (IS_ROOTSIG(obj)) { /* root */
+	    fprintf(stderr, "<root@%s>", GET_ROOTSIG(obj));
+	}
+	else {
+	    fprintf(stderr, "<%s>", obj_info(obj));
+	}
+	if (i+1 < refs->pos) fprintf(stderr, ", ");
+    }
+}
+
+static int
+reflist_refered_from_machine_context(struct reflist *refs)
+{
+    int i;
+    for (i=0; i<refs->pos; i++) {
+	VALUE obj = refs->list[i];
+	if (IS_ROOTSIG(obj) && strcmp(GET_ROOTSIG(obj), "machine_context") == 0) return 1;
+    }
+    return 0;
+}
+
+struct allrefs {
+    rb_objspace_t *objspace;
+    /* a -> obj1
+     * b -> obj1
+     * c -> obj1
+     * c -> obj2
+     * d -> obj3
+     * #=> {obj1 => [a, b, c], obj2 => [c, d]}
+     */
+    struct st_table *references;
+    const char *category;
+    VALUE root_obj;
+    mark_stack_t mark_stack;
+};
+
+static int
+allrefs_add(struct allrefs *data, VALUE obj)
+{
+    struct reflist *refs;
+
+    if (st_lookup(data->references, obj, (st_data_t *)&refs)) {
+	reflist_add(refs, data->root_obj);
+	return 0;
+    }
+    else {
+	refs = reflist_create(data->root_obj);
+	st_insert(data->references, obj, (st_data_t)refs);
+	return 1;
+    }
+}
+
+static void
+allrefs_i(VALUE obj, void *ptr)
+{
+    struct allrefs *data = (struct allrefs *)ptr;
+
+    if (allrefs_add(data, obj)) {
+	push_mark_stack(&data->mark_stack, obj);
+    }
+}
+
+static void
+allrefs_roots_i(VALUE obj, void *ptr)
+{
+    struct allrefs *data = (struct allrefs *)ptr;
+    if (strlen(data->category) == 0) rb_bug("!!!");
+    data->root_obj = MAKE_ROOTSIG(data->category);
+
+    if (allrefs_add(data, obj)) {
+	push_mark_stack(&data->mark_stack, obj);
+    }
+}
+
+static st_table *
+objspace_allrefs(rb_objspace_t *objspace)
+{
+    struct allrefs data;
+    struct mark_func_data_struct mfd;
+    VALUE obj;
+    int prev_dont_gc = dont_gc;
+    dont_gc = TRUE;
+
+    data.objspace = objspace;
+    data.references = st_init_numtable();
+    init_mark_stack(&data.mark_stack);
+
+    mfd.mark_func = allrefs_roots_i;
+    mfd.data = &data;
+
+    /* traverse root objects */
+    PUSH_MARK_FUNC_DATA(&mfd);
+    objspace->mark_func_data = &mfd;
+    gc_mark_roots(objspace, &data.category);
+    POP_MARK_FUNC_DATA();
+
+    /* traverse rest objects reachable from root objects */
+    while (pop_mark_stack(&data.mark_stack, &obj)) {
+	rb_objspace_reachable_objects_from(data.root_obj = obj, allrefs_i, &data);
+    }
+    free_stack_chunks(&data.mark_stack);
+
+    dont_gc = prev_dont_gc;
+    return data.references;
+}
+
+static int
+objspaec_allrefs_destruct_i(st_data_t key, st_data_t value, void *ptr)
+{
+    struct reflist *refs = (struct reflist *)value;
+    reflist_destruct(refs);
+    return ST_CONTINUE;
+}
+
+static void
+objspace_allrefs_destruct(struct st_table *refs)
+{
+    st_foreach(refs, objspaec_allrefs_destruct_i, 0);
+    st_free_table(refs);
+}
+
+#if RGENGC_CHECK_MODE >= 5
+static int
+allrefs_dump_i(st_data_t k, st_data_t v, st_data_t ptr)
+{
+    VALUE obj = (VALUE)k;
+    struct reflist *refs = (struct reflist *)v;
+    fprintf(stderr, "[allrefs_dump_i] %s <- ", obj_info(obj));
+    reflist_dump(refs);
+    fprintf(stderr, "\n");
+    return ST_CONTINUE;
+}
+
+static void
+allrefs_dump(rb_objspace_t *objspace)
+{
+    fprintf(stderr, "[all refs] (size: %d)\n", (int)objspace->rgengc.allrefs_table->num_entries);
+    st_foreach(objspace->rgengc.allrefs_table, allrefs_dump_i, 0);
+}
+#endif
+
+static int
+gc_check_after_marks_i(st_data_t k, st_data_t v, void *ptr)
+{
+    VALUE obj = k;
+    struct reflist *refs = (struct reflist *)v;
+    rb_objspace_t *objspace = (rb_objspace_t *)ptr;
+
+    /* object should be marked or oldgen */
+    if (!MARKED_IN_BITMAP(GET_HEAP_MARK_BITS(obj), obj)) {
+	fprintf(stderr, "gc_check_after_marks_i: %s is not marked and not oldgen.\n", obj_info(obj));
+	fprintf(stderr, "gc_check_after_marks_i: %p is referred from ", (void *)obj);
+	reflist_dump(refs);
+
+	if (reflist_refered_from_machine_context(refs)) {
+	    fprintf(stderr, " (marked from machine stack).\n");
+	    /* marked from machine context can be false positive */
+	}
+	else {
+	    objspace->rgengc.error_count++;
+	    fprintf(stderr, "\n");
+	}
+    }
+    return ST_CONTINUE;
+}
+
+static void
+gc_marks_check(rb_objspace_t *objspace, int (*checker_func)(ANYARGS), const char *checker_name)
+{
+    size_t saved_malloc_increase = objspace->malloc_params.increase;
+#if RGENGC_ESTIMATE_OLDMALLOC
+    size_t saved_oldmalloc_increase = objspace->rgengc.oldmalloc_increase;
+#endif
+    VALUE already_disabled = rb_gc_disable();
+
+    objspace->rgengc.allrefs_table = objspace_allrefs(objspace);
+
+    if (checker_func) {
+	st_foreach(objspace->rgengc.allrefs_table, checker_func, (st_data_t)objspace);
+    }
+
+    if (objspace->rgengc.error_count > 0) {
+#if RGENGC_CHECK_MODE >= 5
+	allrefs_dump(objspace);
+#endif
+	if (checker_name) rb_bug("%s: GC has problem.", checker_name);
+    }
+
+    objspace_allrefs_destruct(objspace->rgengc.allrefs_table);
+    objspace->rgengc.allrefs_table = 0;
+
+    if (already_disabled == Qfalse) rb_gc_enable();
+    objspace->malloc_params.increase = saved_malloc_increase;
+#if RGENGC_ESTIMATE_OLDMALLOC
+    objspace->rgengc.oldmalloc_increase = saved_oldmalloc_increase;
+#endif
+}
+#endif /* RGENGC_CHECK_MODE >= 4 */
+
+struct verify_internal_consistency_struct {
+    rb_objspace_t *objspace;
+    int err_count;
+    size_t live_object_count;
+    size_t zombie_object_count;
+
+#if USE_RGENGC
+    VALUE parent;
+    size_t old_object_count;
+    size_t remembered_shady_count;
+#endif
+};
+
+#if USE_RGENGC
+static void
+check_generation_i(const VALUE child, void *ptr)
+{
+    struct verify_internal_consistency_struct *data = (struct verify_internal_consistency_struct *)ptr;
+    const VALUE parent = data->parent;
+
+    if (RGENGC_CHECK_MODE) assert(RVALUE_OLD_P(parent));
+
+    if (!RVALUE_OLD_P(child)) {
+	if (!RVALUE_REMEMBERED(parent) &&
+	    !RVALUE_REMEMBERED(child) &&
+	    !RVALUE_LONG_LIVED(child)) {
+	    fprintf(stderr, "verify_internal_consistency_reachable_i: WB miss (O->Y) %s -> %s\n", obj_info(parent), obj_info(child));
+	    data->err_count++;
+	}
+    }
+}
+
+static void
+check_color_i(const VALUE child, void *ptr)
+{
+    struct verify_internal_consistency_struct *data = (struct verify_internal_consistency_struct *)ptr;
+    const VALUE parent = data->parent;
+
+    if (!RVALUE_WB_UNPROTECTED(parent) && RVALUE_WHITE_P(child)) {
+	fprintf(stderr, "verify_internal_consistency_reachable_i: WB miss (B->W) - %s -> %s\n",
+		obj_info(parent), obj_info(child));
+	data->err_count++;
+    }
+}
+#endif
+
+static void
+check_children_i(const VALUE child, void *ptr)
+{
+    check_rvalue_consistency(child);
+}
+
+static int
+verify_internal_consistency_i(void *page_start, void *page_end, size_t stride, void *ptr)
+{
+    struct verify_internal_consistency_struct *data = (struct verify_internal_consistency_struct *)ptr;
+    VALUE obj;
+    rb_objspace_t *objspace = data->objspace;
+
+    for (obj = (VALUE)page_start; obj != (VALUE)page_end; obj += stride) {
+	if (is_live_object(objspace, obj)) {
+	    /* count objects */
+	    data->live_object_count++;
+
+	    rb_objspace_reachable_objects_from(obj, check_children_i, (void *)data);
+
+#if USE_RGENGC
+	    /* check health of children */
+	    data->parent = obj;
+
+	    if (RVALUE_OLD_P(obj)) data->old_object_count++;
+	    if (RVALUE_WB_UNPROTECTED(obj) && RVALUE_LONG_LIVED(obj)) data->remembered_shady_count++;
+
+	    if (!is_marking(objspace) && RVALUE_OLD_P(obj)) {
+		/* reachable objects from an oldgen object should be old or (young with remember) */
+		data->parent = obj;
+		rb_objspace_reachable_objects_from(obj, check_generation_i, (void *)data);
+	    }
+
+	    if (is_incremental_marking(objspace)) {
+		if (RVALUE_BLACK_P(obj)) {
+		    /* reachable objects from black objects should be black or grey objects */
+		    data->parent = obj;
+		    rb_objspace_reachable_objects_from(obj, check_color_i, (void *)data);
+		}
+	    }
+#endif
+	}
+	else {
+	    if (BUILTIN_TYPE(obj) == T_ZOMBIE) {
+		if (RGENGC_CHECK_MODE) assert(RBASIC(obj)->flags == T_ZOMBIE);
+		data->zombie_object_count++;
+	    }
+	}
+    }
+
+    return 0;
+}
+
+static int
+gc_verify_heap_page(rb_objspace_t *objspace, struct heap_page *page, VALUE obj)
+{
+#if USE_RGENGC
+    int i;
+    unsigned int has_remembered_shady = FALSE;
+    unsigned int has_remembered_old = FALSE;
+    int rememberd_old_objects = 0;
+
+    for (i=0; i<page->total_slots; i++) {
+	VALUE obj = (VALUE)&page->start[i];
+	if (RVALUE_PAGE_LONG_LIVED(page, obj) && RVALUE_PAGE_WB_UNPROTECTED(page, obj)) has_remembered_shady = TRUE;
+	if (RVALUE_PAGE_MARKING(page, obj)) {
+	    has_remembered_old = TRUE;
+	    rememberd_old_objects++;
+	}
+    }
+
+    if (!is_incremental_marking(objspace) &&
+	page->flags.has_remembered_objects == FALSE && has_remembered_old == TRUE) {
+
+	for (i=0; i<page->total_slots; i++) {
+	    VALUE obj = (VALUE)&page->start[i];
+	    if (RVALUE_PAGE_MARKING(page, obj)) {
+		fprintf(stderr, "marking -> %s\n", obj_info(obj));
+	    }
+	}
+	rb_bug("page %p's has_remembered_objects should be false, but there are remembered old objects (%d). %s",
+	       page, rememberd_old_objects, obj ? obj_info(obj) : "");
+    }
+
+    if (page->flags.has_long_lived_shady_objects == FALSE && has_remembered_shady == TRUE) {
+	rb_bug("page %p's has_remembered_shady should be false, but there are remembered shady objects. %s",
+	       page, obj ? obj_info(obj) : "");
+    }
+
+    return rememberd_old_objects;
+#else
+    return 0;
+#endif
+}
+
+static int
+gc_verify_heap_pages(rb_objspace_t *objspace)
+{
+    int rememberd_old_objects = 0;
+    struct heap_page *page = heap_eden->pages;
+
+    while (page) {
+	if (page->flags.has_remembered_objects == FALSE)
+	  rememberd_old_objects += gc_verify_heap_page(objspace, page, Qfalse);
+	page = page->next;
+    }
+
+    return rememberd_old_objects;
+}
+
+/*
+ *  call-seq:
+ *     GC.verify_internal_consistency                  -> nil
+ *
+ *  Verify internal consistency.
+ *
+ *  This method is implementation specific.
+ *  Now this method checks generational consistency
+ *  if RGenGC is supported.
+ */
+static VALUE
+gc_verify_internal_consistency(VALUE self)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    struct verify_internal_consistency_struct data = {0};
+    struct each_obj_args eo_args;
+
+    data.objspace = objspace;
+    gc_report(5, objspace, "gc_verify_internal_consistency: start\n");
+
+    /* check relations */
+
+    eo_args.callback = verify_internal_consistency_i;
+    eo_args.data = (void *)&data;
+    objspace_each_objects((VALUE)&eo_args);
+
+    if (data.err_count != 0) {
+#if RGENGC_CHECK_MODE >= 5
+	objspace->rgengc.error_count = data.err_count;
+	gc_marks_check(objspace, NULL, NULL);
+	allrefs_dump(objspace);
+#endif
+	rb_bug("gc_verify_internal_consistency: found internal inconsistency.");
+    }
+
+    /* check heap_page status */
+    gc_verify_heap_pages(objspace);
+
+    /* check counters */
+
+    if (!is_lazy_sweeping(heap_eden) && !finalizing) {
+	if (objspace_live_slots(objspace) != data.live_object_count) {
+	    fprintf(stderr, "heap_pages_final_slots: %d, objspace->profile.total_freed_objects: %d\n",
+		    (int)heap_pages_final_slots, (int)objspace->profile.total_freed_objects);
+	    rb_bug("inconsistent live slot nubmer: expect %"PRIuSIZE", but %"PRIuSIZE".", objspace_live_slots(objspace), data.live_object_count);
+	}
+    }
+
+#if USE_RGENGC
+    if (!is_marking(objspace)) {
+	if (objspace->rgengc.old_objects != data.old_object_count) {
+	    rb_bug("inconsistent old slot nubmer: expect %"PRIuSIZE", but %"PRIuSIZE".", objspace->rgengc.old_objects, data.old_object_count);
+	}
+	if (objspace->rgengc.remembered_wb_unprotected_objects != data.remembered_shady_count) {
+	    rb_bug("inconsistent old slot nubmer: expect %"PRIuSIZE", but %"PRIuSIZE".", objspace->rgengc.remembered_wb_unprotected_objects, data.remembered_shady_count);
+	}
+    }
+#endif
+
+    if (!finalizing) {
+	size_t list_count = 0;
+
+	{
+	    VALUE z = heap_pages_deferred_final;
+	    while (z) {
+		list_count++;
+		z = RZOMBIE(z)->next;
+	    }
+	}
+
+	if (heap_pages_final_slots != data.zombie_object_count ||
+	    heap_pages_final_slots != list_count) {
+
+	    rb_bug("inconsistent finalizing object count:\n"
+		   "  expect %"PRIuSIZE"\n"
+		   "  but    %"PRIuSIZE" zombies\n"
+		   "  heap_pages_deferred_final list has %"PRIuSIZE" items.",
+		   heap_pages_final_slots,
+		   data.zombie_object_count,
+		   list_count);
+	}
+    }
+
+    gc_report(5, objspace, "gc_verify_internal_consistency: OK\n");
+
+    return Qnil;
+}
+
+/* marks */
+
+static void
+gc_marks_start(rb_objspace_t *objspace, int full_mark)
+{
+    /* start marking */
+    gc_report(1, objspace, "gc_marks_start: (%s)\n", full_mark ? "full" : "minor");
+    gc_stat_transition(objspace, gc_stat_marking);
+
+#if USE_RGENGC
+    if (full_mark) {
+#if GC_ENABLE_INCREMENTAL_MARK
+	objspace->rincgc.step_slots = (objspace->marked_slots * 2) / ((objspace->rincgc.pooled_slots / HEAP_OBJ_LIMIT) + 1);
+
+	if (0) fprintf(stderr, "objspace->marked_slots: %d, objspace->rincgc.pooled_page_num: %d, objspace->rincgc.step_slots: %d, \n",
+		       (int)objspace->marked_slots, (int)objspace->rincgc.pooled_slots, (int)objspace->rincgc.step_slots);
+#endif
+	objspace->flags.during_minor_gc = FALSE;
+	objspace->profile.major_gc_count++;
+	objspace->rgengc.remembered_wb_unprotected_objects = 0;
+	objspace->rgengc.old_objects = 0;
+	objspace->rgengc.last_major_gc = objspace->profile.count;
+	objspace->marked_slots = 0;
+	rgengc_mark_and_rememberset_clear(objspace, heap_eden);
+    }
+    else {
+	objspace->flags.during_minor_gc = TRUE;
+	objspace->marked_slots =
+	  objspace->rgengc.old_objects +
+	  objspace->rgengc.remembered_wb_unprotected_objects; /* long lived objects are marked already */
+	objspace->profile.minor_gc_count++;
+	rgengc_rememberset_mark(objspace, heap_eden);
+    }
+#endif
+
+    gc_mark_roots(objspace, NULL);
+
+    gc_report(1, objspace, "gc_marks_start: (%s) end, stack in %d\n", full_mark ? "full" : "minor", (int)mark_stack_size(&objspace->mark_stack));
+}
+
+#if GC_ENABLE_INCREMENTAL_MARK
+static void
+gc_marks_wb_unprotected_objects(rb_objspace_t *objspace)
+{
+    struct heap_page *page = heap_eden->pages;
+
+    while (page) {
+	bits_t *mark_bits = page->mark_bits;
+	bits_t *wbun_bits = page->wb_unprotected_bits;
+	RVALUE *p = page->start;
+	RVALUE *offset = p - NUM_IN_PAGE(p);
+	size_t j;
+
+	for (j=0; j<HEAP_BITMAP_LIMIT; j++) {
+	    bits_t bits = mark_bits[j] & wbun_bits[j];
+
+	    if (bits) {
+		p = offset  + j * BITS_BITLENGTH;
+
+		do {
+		    if (bits & 1) {
+			gc_report(2, objspace, "gc_marks_wb_unprotected_objects: marked shady: %s\n", obj_info((VALUE)p));
+			if (RGENGC_CHECK_MODE > 0) {
+			    assert(RVALUE_WB_UNPROTECTED((VALUE)p));
+			    assert(RVALUE_MARKED((VALUE)p));
+			}
+			gc_mark_children(objspace, (VALUE)p);
+		    }
+		    p++;
+		    bits >>= 1;
+		} while (bits);
+	    }
+	}
+
+	page = page->next;
+    }
+
+    gc_mark_stacked_objects_all(objspace);
+}
+
+static struct heap_page *
+heap_move_pooled_pages_to_free_pages(rb_heap_t *heap)
+{
+    struct heap_page *page = heap->pooled_pages;
+
+    if (page) {
+	heap->pooled_pages = page->free_next;
+	page->free_next = heap->free_pages;
+	heap->free_pages = page;
+    }
+
+    return page;
+}
+#endif
+
+static int
+gc_marks_finish(rb_objspace_t *objspace)
+{
+#if GC_ENABLE_INCREMENTAL_MARK
+    /* finish incremental GC */
+    if (is_incremental_marking(objspace)) {
+	if (heap_eden->pooled_pages) {
+	    heap_move_pooled_pages_to_free_pages(heap_eden);
+	    gc_report(1, objspace, "gc_marks_finish: pooled pages are exists. retry.\n");
+	    return FALSE; /* continue marking phase */
+	}
+
+	if (RGENGC_CHECK_MODE && is_mark_stack_empty(&objspace->mark_stack) == 0) {
+	    rb_bug("gc_marks_finish: mark stack is not empty (%d).", (int)mark_stack_size(&objspace->mark_stack));
+	}
+
+	gc_mark_roots(objspace, 0);
+
+	if (is_mark_stack_empty(&objspace->mark_stack) == FALSE) {
+	    gc_report(1, objspace, "gc_marks_finish: not empty (%d). retry.\n", (int)mark_stack_size(&objspace->mark_stack));
+	    return FALSE;
+	}
+
+#if RGENGC_CHECK_MODE >= 2
+	if (gc_verify_heap_pages(objspace) != 0) {
+	    rb_bug("gc_marks_finish (incremental): there are remembered old objects.");
+	}
+#endif
+
+	objspace->flags.during_incremental_marking = FALSE;
+	/* check children of all marked wb-unprotected objects */
+	gc_marks_wb_unprotected_objects(objspace);
+    }
+#endif /* GC_ENABLE_INCREMENTAL_MARK */
+
+#if RGENGC_CHECK_MODE >= 2
+    gc_verify_internal_consistency(Qnil);
+#endif
+
+#if USE_RGENGC
+    if (is_full_marking(objspace)) {
+	/* See the comment about RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR */
+	const double r = gc_params.oldobject_limit_factor;
+	objspace->rgengc.remembered_wb_unprotected_objects_limit = (size_t)(objspace->rgengc.remembered_wb_unprotected_objects * r);
+	objspace->rgengc.old_objects_limit = (size_t)(objspace->rgengc.old_objects * r);
+    }
+#endif
+
+#if RGENGC_CHECK_MODE >= 4
+    gc_marks_check(objspace, gc_check_after_marks_i, "after_marks");
+#endif
+
+    {   /* decide full GC is needed or not */
+	rb_heap_t *heap = heap_eden;
+	size_t sweep_slots =
+	  (heap_allocatable_pages * HEAP_OBJ_LIMIT) +   /* allocatable slots in empty pages */
+	  (heap->total_slots - objspace->marked_slots); /* will be sweep slots */
+
+#if RGENGC_CHECK_MODE
+	assert(heap->total_slots >= objspace->marked_slots);
+#endif
+
+	if (sweep_slots < heap_pages_min_free_slots) {
+#if USE_RGENGC
+	    if (!is_full_marking(objspace) && objspace->profile.count - objspace->rgengc.last_major_gc > 3 /* magic number */) {
+		gc_report(1, objspace, "gc_marks_finish: next is full GC!!)\n");
+		objspace->rgengc.need_major_gc |= GPR_FLAG_MAJOR_BY_NOFREE;
+	    }
+	    else {
+		gc_report(1, objspace, "gc_marks_finish: heap_set_increment!!\n");
+		heap_set_increment(objspace, heap_extend_pages(objspace));
+		heap_increment(objspace, heap);
+	    }
+#else
+	    gc_report(1, objspace, "gc_marks_finish: heap_set_increment!!\n");
+	    heap_set_increment(objspace, heap_extend_pages(objspace));
+	    heap_increment(objspace, heap);
+#endif
+	}
+
+#if USE_RGENGC
+	if (objspace->rgengc.remembered_wb_unprotected_objects > objspace->rgengc.remembered_wb_unprotected_objects_limit) {
+	    objspace->rgengc.need_major_gc |= GPR_FLAG_MAJOR_BY_SHADY;
+	}
+	if (objspace->rgengc.old_objects > objspace->rgengc.old_objects_limit) {
+	    objspace->rgengc.need_major_gc |= GPR_FLAG_MAJOR_BY_OLDGEN;
+	}
+	if (RGENGC_FORCE_MAJOR_GC) {
+	    objspace->rgengc.need_major_gc = GPR_FLAG_MAJOR_BY_FORCE;
+	}
+
+	gc_report(1, objspace, "gc_marks_finish (marks %d objects, old %d objects, total %d slots, sweep %d slots, increment: %d, next GC: %s)\n",
+		  (int)objspace->marked_slots, (int)objspace->rgengc.old_objects, (int)heap->total_slots, (int)sweep_slots, (int)heap_allocatable_pages,
+		  objspace->rgengc.need_major_gc ? "major" : "minor");
+#endif
+    }
+
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_GC_END_MARK, 0);
+
+    return TRUE;
+}
+
+#if GC_ENABLE_INCREMENTAL_MARK
+static void
+gc_marks_step(rb_objspace_t *objspace, int slots)
+{
+    if (RGENGC_CHECK_MODE) assert(is_marking(objspace));
+
+    if (gc_mark_stacked_objects_incremental(objspace, slots)) {
+	if (gc_marks_finish(objspace)) {
+	    /* finish */
+	    gc_sweep(objspace);
+	}
+    }
+    if (0) fprintf(stderr, "objspace->marked_slots: %d\n", (int)objspace->marked_slots);
+}
+#endif
+
+static void
+gc_marks_rest(rb_objspace_t *objspace)
+{
+    gc_report(1, objspace, "gc_marks_rest\n");
+
+#if GC_ENABLE_INCREMENTAL_MARK
+    heap_eden->pooled_pages = NULL;
+#endif
+
+    if (is_incremental_marking(objspace)) {
+	do {
+	    while (gc_mark_stacked_objects_incremental(objspace, INT_MAX) == FALSE);
+	} while (gc_marks_finish(objspace) == FALSE);
+    }
+    else {
+	gc_mark_stacked_objects_all(objspace);
+	gc_marks_finish(objspace);
+    }
+
+    /* move to sweep */
+    gc_sweep(objspace);
+}
+
+#if GC_ENABLE_INCREMENTAL_MARK
+static void
+gc_marks_continue(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    int slots = 0;
+    const char *from;
+
+    if (RGENGC_CHECK_MODE) assert(dont_gc == FALSE);
+
+    gc_enter(objspace, "marks_continue");
+
+    PUSH_MARK_FUNC_DATA(NULL);
+    {
+	if (heap->pooled_pages) {
+	    while (heap->pooled_pages && slots < HEAP_OBJ_LIMIT) {
+		struct heap_page *page = heap_move_pooled_pages_to_free_pages(heap);
+		slots += page->free_slots;
+	    }
+	    from = "pooled-pages";
+	}
+	else if (heap_increment(objspace, heap)) {
+	    slots = heap->free_pages->free_slots;
+	    from = "incremented-pages";
+	}
+
+	if (slots > 0) {
+	    gc_report(2, objspace, "gc_marks_continue: provide %d slots from %s.\n", slots, from);
+	    gc_marks_step(objspace, (int)objspace->rincgc.step_slots);
+	}
+	else {
+	    gc_report(2, objspace, "gc_marks_continue: no more pooled pages (stack depth: %d).\n", (int)mark_stack_size(&objspace->mark_stack));
+	    gc_marks_rest(objspace);
+	}
+    }
+    POP_MARK_FUNC_DATA();
+
+    gc_exit(objspace, "marks_continue");
+}
+#endif
+
+static void
+gc_marks(rb_objspace_t *objspace, int full_mark)
+{
+    gc_prof_mark_timer_start(objspace);
+
+    PUSH_MARK_FUNC_DATA(NULL);
+    {
+	/* setup marking */
+
+#if USE_RGENGC
+	gc_marks_start(objspace, full_mark);
+	if (!is_incremental_marking(objspace)) {
+	    gc_marks_rest(objspace);
+	}
+
+#if RGENGC_PROFILE > 0
+	if (gc_prof_record(objspace)) {
+	    gc_profile_record *record = gc_prof_record(objspace);
+	    record->old_objects = objspace->rgengc.old_objects;
+	}
+#endif
+
+#else /* USE_RGENGC */
+	gc_marks_start(objspace, TRUE);
+	gc_marks_rest(objspace);
+#endif
+    }
+    POP_MARK_FUNC_DATA();
+    gc_prof_mark_timer_stop(objspace);
+}
+
+/* RGENGC */
+
+static void
+gc_report_body(int level, rb_objspace_t *objspace, const char *fmt, ...)
+{
+    if (level <= RGENGC_DEBUG) {
+	char buf[1024];
+	FILE *out = stderr;
+	va_list args;
+	const char *status = " ";
+
+#if USE_RGENGC
+	if (during_gc) {
+	    status = is_full_marking(objspace) ? "+" : "-";
+	}
+	else {
+	    if (is_lazy_sweeping(heap_eden)) {
+		status = "S";
+	    }
+	    if (is_incremental_marking(objspace)) {
+		status = "M";
+	    }
+	}
+#endif
+
+	va_start(args, fmt);
+	vsnprintf(buf, 1024, fmt, args);
+	va_end(args);
+
+	fprintf(out, "%s|", status);
+	fputs(buf, out);
+    }
+}
+
+#if USE_RGENGC
+
+/* bit operations */
+
+static int
+rgengc_remembersetbits_get(rb_objspace_t *objspace, VALUE obj)
+{
+    return RVALUE_REMEMBERED(obj);
+}
+
+static int
+rgengc_remembersetbits_set(rb_objspace_t *objspace, VALUE obj)
+{
+    struct heap_page *page = GET_HEAP_PAGE(obj);
+    bits_t *bits = &page->marking_bits[0];
+
+    if (RGENGC_CHECK_MODE) assert(!is_incremental_marking(objspace));
+
+    if (MARKED_IN_BITMAP(bits, obj)) {
+	return FALSE;
+    }
+    else {
+	page->flags.has_remembered_objects = TRUE;
+	MARK_IN_BITMAP(bits, obj);
+	return TRUE;
+    }
+}
+
+/* wb, etc */
+
+/* return FALSE if already remembered */
+static int
+rgengc_remember(rb_objspace_t *objspace, VALUE obj)
+{
+    gc_report(6, objspace, "rgengc_remember: %s %s\n", obj_info(obj),
+	      rgengc_remembersetbits_get(objspace, obj) ? "was already remembered" : "is remembered now");
+
+    check_rvalue_consistency(obj);
+
+    if (RGENGC_CHECK_MODE) {
+	if (RVALUE_WB_UNPROTECTED(obj)) rb_bug("rgengc_remember: %s is not wb protected.", obj_info(obj));
+    }
+
+#if RGENGC_PROFILE > 0
+    if (!rgengc_remembered(objspace, obj)) {
+	if (RVALUE_WB_UNPROTECTED(obj) == 0) {
+	    objspace->profile.total_remembered_normal_object_count++;
+#if RGENGC_PROFILE >= 2
+	    objspace->profile.remembered_normal_object_count_types[BUILTIN_TYPE(obj)]++;
+#endif
+	}
+    }
+#endif /* RGENGC_PROFILE > 0 */
+
+    return rgengc_remembersetbits_set(objspace, obj);
+}
+
+static int
+rgengc_remembered(rb_objspace_t *objspace, VALUE obj)
+{
+    int result = rgengc_remembersetbits_get(objspace, obj);
+    check_rvalue_consistency(obj);
+    gc_report(6, objspace, "rgengc_remembered: %s\n", obj_info(obj));
+    return result;
+}
+
+#ifndef PROFILE_REMEMBERSET_MARK
+#define PROFILE_REMEMBERSET_MARK 0
+#endif
+
+static void
+rgengc_rememberset_mark(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    size_t j;
+    struct heap_page *page = heap->pages;
+#if PROFILE_REMEMBERSET_MARK
+    int has_old = 0, has_shady = 0, has_both = 0, skip = 0;
+#endif
+    gc_report(1, objspace, "rgengc_rememberset_mark: start\n");
+
+    while (page) {
+	if (page->flags.has_remembered_objects | page->flags.has_long_lived_shady_objects) {
+	    RVALUE *p = page->start;
+	    RVALUE *offset = p - NUM_IN_PAGE(p);
+	    bits_t bitset, bits[HEAP_BITMAP_LIMIT];
+	    bits_t *marking_bits = page->marking_bits;
+	    bits_t *long_lived_bits = page->long_lived_bits;
+	    bits_t *wb_unprotected_bits = page->wb_unprotected_bits;
+#if PROFILE_REMEMBERSET_MARK
+	    if (page->flags.has_remembered_objects && page->flags.has_long_lived_shady_objects) has_both++;
+	    else if (page->flags.has_remembered_objects) has_old++;
+	    else if (page->flags.has_long_lived_shady_objects) has_shady++;
+#endif
+	    for (j=0; j<HEAP_BITMAP_LIMIT; j++) {
+		bits[j] = marking_bits[j] | (long_lived_bits[j] & wb_unprotected_bits[j]);
+		marking_bits[j] = 0;
+	    }
+	    page->flags.has_remembered_objects = FALSE;
+
+	    for (j=0; j < HEAP_BITMAP_LIMIT; j++) {
+		bitset = bits[j];
+
+		if (bitset) {
+		    p = offset  + j * BITS_BITLENGTH;
+
+		    do {
+			if (bitset & 1) {
+			    VALUE obj = (VALUE)p;
+			    gc_report(2, objspace, "rgengc_rememberset_mark: mark %s\n", obj_info(obj));
+
+			    if (RGENGC_CHECK_MODE) {
+				assert(RVALUE_LONG_LIVED(obj));
+				assert(RVALUE_OLD_P(obj) || RVALUE_WB_UNPROTECTED(obj));
+			    }
+
+			    gc_mark_children(objspace, obj);
+			}
+			p++;
+			bitset >>= 1;
+		    } while (bitset);
+		}
+	    }
+	}
+#if PROFILE_REMEMBERSET_MARK
+	else {
+	    skip++;
+	}
+#endif
+
+	page = page->next;
+    }
+
+#if PROFILE_REMEMBERSET_MARK
+    fprintf(stderr, "%d\t%d\t%d\t%d\n", has_both, has_old, has_shady, skip);
+#endif
+    gc_report(1, objspace, "rgengc_rememberset_mark: finished\n");
+}
+
+static void
+rgengc_mark_and_rememberset_clear(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    struct heap_page *page = heap->pages;
+
+    while (page) {
+	memset(&page->mark_bits[0],       0, HEAP_BITMAP_SIZE);
+	memset(&page->marking_bits[0],    0, HEAP_BITMAP_SIZE);
+	memset(&page->long_lived_bits[0], 0, HEAP_BITMAP_SIZE);
+	page->flags.has_long_lived_shady_objects = FALSE;
+	page->flags.has_remembered_objects = FALSE;
+	page = page->next;
+    }
+}
+
+/* RGENGC: APIs */
+
+void
+rb_gc_writebarrier_generational(VALUE a, VALUE b)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    if (RGENGC_CHECK_MODE) {
+	if (!RVALUE_OLD_P(a)) rb_bug("rb_gc_writebarrier_generational: %s is not an old object.", obj_info(a));
+	if ( RVALUE_OLD_P(b)) rb_bug("rb_gc_writebarrier_generational: %s is an old object.", obj_info(b));
+	if (is_incremental_marking(objspace)) rb_bug("rb_gc_writebarrier_generational: called while incremental marking: %s -> %s", obj_info(a), obj_info(b));
+    }
+
+    if (!rgengc_remembered(objspace, a)) {
+	gc_report(1, objspace, "rb_gc_writebarrier_generational: %s -> %s\n", obj_info(a), obj_info(b));
+	rgengc_remember(objspace, a);
+    }
+}
+
+#if GC_ENABLE_INCREMENTAL_MARK
+static void
+gc_mark_from(rb_objspace_t *objspace, VALUE obj, VALUE parent)
+{
+    gc_mark_set_parent(objspace, parent);
+    rgengc_check_relation(objspace, obj);
+    if (gc_mark_set(objspace, obj) == FALSE) return;
+    gc_aging(objspace, obj);
+    gc_grey(objspace, obj);
+}
+
+int
+rb_gc_writebarrier_incremental(VALUE a, VALUE b)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    if (RGENGC_CHECK_MODE) {
+	if (SPECIAL_CONST_P(a)) rb_bug("rb_gc_writebarrier: a is special const");
+	if (SPECIAL_CONST_P(b)) rb_bug("rb_gc_writebarrier: a is special const");
+    }
+
+    if (LIKELY(!is_incremental_marking(objspace))) {
+	return FALSE;
+    }
+    else {
+	gc_report(2, objspace, "rb_gc_writebarrier_incremental: [LG] %s -> %s\n", obj_info(a), obj_info(b));
+
+	if (RVALUE_BLACK_P(a)) {
+	    if (RVALUE_WHITE_P(b)) {
+		if (!RVALUE_WB_UNPROTECTED(a)) {
+		    gc_report(2, objspace, "rb_gc_writebarrier_incremental: [IN] %s -> %s\n", obj_info(a), obj_info(b));
+		    gc_mark_from(objspace, b, a);
+		}
+	    }
+	    else if (RVALUE_OLD_P(a) && !RVALUE_OLD_P(b)) {
+		if (!RVALUE_WB_UNPROTECTED(b)) {
+		    gc_report(1, objspace, "rb_gc_writebarrier_incremental: [GN] %s -> %s\n", obj_info(a), obj_info(b));
+		    RVALUE_AGE_SET_OLD(objspace, b);
+
+		    if (RVALUE_BLACK_P(b)) {
+			gc_grey(objspace, b);
+		    }
+		}
+		else {
+		    gc_report(1, objspace, "rb_gc_writebarrier_incremental: [LL] %s -> %s\n", obj_info(a), obj_info(b));
+		    gc_remember_unprotected(objspace, b);
+		}
+	    }
+	}
+
+	return TRUE;
+    }
+}
+#endif
+
+void
+rb_gc_writebarrier_unprotect(VALUE obj)
+{
+    if (RVALUE_WB_UNPROTECTED(obj)) {
+	return;
+    }
+    else {
+	rb_objspace_t *objspace = &rb_objspace;
+
+	gc_report(2, objspace, "rb_gc_writebarrier_unprotect: %s %s\n", obj_info(obj),
+		  rgengc_remembered(objspace, obj) ? " (already remembered)" : "");
+
+	if (RVALUE_OLD_P(obj)) {
+	    gc_report(1, objspace, "rb_gc_writebarrier_unprotect: %s\n", obj_info(obj));
+	    RVALUE_DEMOTE(objspace, obj);
+	    gc_mark_set(objspace, obj);
+	    gc_remember_unprotected(objspace, obj);
+
+#if RGENGC_PROFILE
+	    objspace->profile.total_shade_operation_count++;
+#if RGENGC_PROFILE >= 2
+	    objspace->profile.shade_operation_count_types[BUILTIN_TYPE(obj)]++;
+#endif /* RGENGC_PROFILE >= 2 */
+#endif /* RGENGC_PROFILE */
+	}
+	else {
+	    RVALUE_AGE_RESET(obj);
+	}
+
+	MARK_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(obj), obj);
+    }
+}
+
+/*
+ * remember `obj' if needed.
+ */
+void
+rb_gc_writebarrier_remember(VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    gc_report(1, objspace, "rb_gc_writebarrier_remember: %s\n", obj_info(obj));
+
+    if (is_incremental_marking(objspace)) {
+	if (RVALUE_BLACK_P(obj)) {
+	    gc_grey(objspace, obj);
+	}
+    }
+    else {
+	if (RVALUE_OLD_P(obj)) {
+	    rgengc_remember(objspace, obj);
+	}
+    }
+}
+
+static st_table *rgengc_unprotect_logging_table;
+
+static int
+rgengc_unprotect_logging_exit_func_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    fprintf(stderr, "%s\t%d\n", (char *)key, (int)val);
+    return ST_CONTINUE;
+}
+
+static void
+rgengc_unprotect_logging_exit_func(void)
+{
+    st_foreach(rgengc_unprotect_logging_table, rgengc_unprotect_logging_exit_func_i, 0);
+}
+
+void
+rb_gc_unprotect_logging(void *objptr, const char *filename, int line)
+{
+    VALUE obj = (VALUE)objptr;
+
+    if (rgengc_unprotect_logging_table == 0) {
+	rgengc_unprotect_logging_table = st_init_strtable();
+	atexit(rgengc_unprotect_logging_exit_func);
+    }
+
+    if (RVALUE_WB_UNPROTECTED(obj) == 0) {
+	char buff[0x100];
+	st_data_t cnt = 1;
+	char *ptr = buff;
+
+	snprintf(ptr, 0x100 - 1, "%s|%s:%d", obj_info(obj), filename, line);
+
+	if (st_lookup(rgengc_unprotect_logging_table, (st_data_t)ptr, &cnt)) {
+	    cnt++;
+	}
+	else {
+	    ptr = (char *)malloc(strlen(buff) + 1);
+	    strcpy(ptr, buff);
+	}
+	st_insert(rgengc_unprotect_logging_table, (st_data_t)ptr, cnt);
+    }
+}
+#endif /* USE_RGENGC */
+
+void
+rb_copy_wb_protected_attribute(VALUE dest, VALUE obj)
+{
+#if USE_RGENGC
+    if (RVALUE_WB_UNPROTECTED(obj)) {
+	MARK_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(dest), dest);
+	RVALUE_AGE_RESET_RAW(dest);
+    }
+
+    check_rvalue_consistency(dest);
+#endif
+}
+
+/* RGENGC analysis information */
+
+VALUE
+rb_obj_rgengc_writebarrier_protected_p(VALUE obj)
+{
+#if USE_RGENGC
+    return RVALUE_WB_UNPROTECTED(obj) ? Qfalse : Qtrue;
+#else
+    return Qfalse;
+#endif
+}
+
+VALUE
+rb_obj_rgengc_promoted_p(VALUE obj)
+{
+    return OBJ_PROMOTED(obj) ? Qtrue : Qfalse;
+}
+
+size_t
+rb_obj_gc_flags(VALUE obj, ID* flags, size_t max)
+{
+    size_t n = 0;
+    static ID ID_marked;
+#if USE_RGENGC
+    static ID ID_wb_protected, ID_old, ID_marking, ID_long_lived;
+#endif
+
+    if (!ID_marked) {
+#define I(s) ID_##s = rb_intern(#s);
+	I(marked);
+#if USE_RGENGC
+	I(wb_protected);
+	I(old);
+	I(marking);
+	I(long_lived);
+#endif
+#undef I
+    }
+
+#if USE_RGENGC
+    if (RVALUE_WB_UNPROTECTED(obj) == 0 && n<max)                   flags[n++] = ID_wb_protected;
+    if (RVALUE_OLD_P(obj) && n<max)                                 flags[n++] = ID_old;
+    if (RVALUE_LONG_LIVED(obj) && n<max)                            flags[n++] = ID_long_lived;
+    if (MARKED_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), obj) && n<max) flags[n++] = ID_marking;
+#endif
+    if (MARKED_IN_BITMAP(GET_HEAP_MARK_BITS(obj), obj) && n<max)    flags[n++] = ID_marked;
+    return n;
+}
+
+/* GC */
+
+void
+rb_gc_force_recycle(VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+#if USE_RGENGC
+    int is_old = RVALUE_OLD_P(obj);
+
+    gc_report(2, objspace, "rb_gc_force_recycle: %s\n", obj_info(obj));
+
+    if (is_old) {
+	if (RVALUE_MARKED(obj)) {
+	    objspace->rgengc.old_objects--;
+	}
+    }
+    CLEAR_IN_BITMAP(GET_HEAP_LONG_LIVED_BITS(obj), obj);
+    CLEAR_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(obj), obj);
+
+#if GC_ENABLE_INCREMENTAL_MARK
+    if (is_incremental_marking(objspace)) {
+	if (MARKED_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), obj)) {
+	    invalidate_mark_stack(&objspace->mark_stack, obj);
+	    CLEAR_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), obj);
+	}
+	CLEAR_IN_BITMAP(GET_HEAP_MARK_BITS(obj), obj);
+    }
+    else {
+#endif
+	if (is_old || !GET_HEAP_PAGE(obj)->flags.before_sweep) {
+	    CLEAR_IN_BITMAP(GET_HEAP_MARK_BITS(obj), obj);
+	}
+	CLEAR_IN_BITMAP(GET_HEAP_MARKING_BITS(obj), obj);
+#if GC_ENABLE_INCREMENTAL_MARK
+    }
+#endif
+#endif
+
+    objspace->profile.total_freed_objects++;
+
+    heap_page_add_freeobj(objspace, GET_HEAP_PAGE(obj), obj);
+
+    /* Disable counting swept_slots because there are no meaning.
+     * if (!MARKED_IN_BITMAP(GET_HEAP_MARK_BITS(p), p)) {
+     *   objspace->heap.swept_slots++;
+     * }
+     */
+}
+
+#ifndef MARK_OBJECT_ARY_BUCKET_SIZE
+#define MARK_OBJECT_ARY_BUCKET_SIZE 1024
+#endif
+
+void
+rb_gc_register_mark_object(VALUE obj)
+{
+    VALUE ary_ary = GET_THREAD()->vm->mark_object_ary;
+    VALUE ary = rb_ary_last(0, 0, ary_ary);
+
+    if (ary == Qnil || RARRAY_LEN(ary) >= MARK_OBJECT_ARY_BUCKET_SIZE) {
+	ary = rb_ary_tmp_new(MARK_OBJECT_ARY_BUCKET_SIZE);
+	rb_ary_push(ary_ary, 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;
+    }
+}
+
+void
+rb_global_variable(VALUE *var)
+{
+    rb_gc_register_address(var);
+}
+
+#define GC_NOTIFY 0
+
+enum {
+    gc_stress_no_major,
+    gc_stress_no_immediate_sweep,
+    gc_stress_full_mark_after_malloc,
+    gc_stress_max
+};
+
+#define gc_stress_full_mark_after_malloc_p() \
+    (FIXNUM_P(ruby_gc_stress_mode) && (FIX2LONG(ruby_gc_stress_mode) & (1<<gc_stress_full_mark_after_malloc)))
+
+static void
+heap_ready_to_gc(rb_objspace_t *objspace, rb_heap_t *heap)
+{
+    if (!heap->freelist && !heap->free_pages) {
+	if (!heap_increment(objspace, heap)) {
+	    heap_set_increment(objspace, 1);
+	    heap_increment(objspace, heap);
+	}
+    }
+}
+
+static int
+ready_to_gc(rb_objspace_t *objspace)
+{
+    if (dont_gc || during_gc || ruby_disable_gc) {
+	heap_ready_to_gc(objspace, heap_eden);
+	return FALSE;
+    }
+    else {
+	return TRUE;
+    }
+}
+
+static void
+gc_reset_malloc_info(rb_objspace_t *objspace)
+{
+    gc_prof_set_malloc_info(objspace);
+    {
+	size_t inc = ATOMIC_SIZE_EXCHANGE(malloc_increase, 0);
+	size_t old_limit = malloc_limit;
+
+	if (inc > malloc_limit) {
+	    malloc_limit = (size_t)(inc * gc_params.malloc_limit_growth_factor);
+	    if (gc_params.malloc_limit_max > 0 && /* ignore max-check if 0 */
+		malloc_limit > gc_params.malloc_limit_max) {
+		malloc_limit = gc_params.malloc_limit_max;
+	    }
+	}
+	else {
+	    malloc_limit = (size_t)(malloc_limit * 0.98); /* magic number */
+	    if (malloc_limit < gc_params.malloc_limit_min) {
+		malloc_limit = gc_params.malloc_limit_min;
+	    }
+	}
+
+	if (0) {
+	    if (old_limit != malloc_limit) {
+		fprintf(stderr, "[%"PRIuSIZE"] malloc_limit: %"PRIuSIZE" -> %"PRIuSIZE"\n",
+			rb_gc_count(), old_limit, malloc_limit);
+	    }
+	    else {
+		fprintf(stderr, "[%"PRIuSIZE"] malloc_limit: not changed (%"PRIuSIZE")\n",
+			rb_gc_count(), malloc_limit);
+	    }
+	}
+    }
+
+    /* reset oldmalloc info */
+#if RGENGC_ESTIMATE_OLDMALLOC
+    if (!is_full_marking(objspace)) {
+	if (objspace->rgengc.oldmalloc_increase > objspace->rgengc.oldmalloc_increase_limit) {
+	    objspace->rgengc.need_major_gc |= GPR_FLAG_MAJOR_BY_OLDMALLOC;;
+	    objspace->rgengc.oldmalloc_increase_limit =
+	      (size_t)(objspace->rgengc.oldmalloc_increase_limit * gc_params.oldmalloc_limit_growth_factor);
+
+	    if (objspace->rgengc.oldmalloc_increase_limit > gc_params.oldmalloc_limit_max) {
+		objspace->rgengc.oldmalloc_increase_limit = gc_params.oldmalloc_limit_max;
+	    }
+	}
+
+	if (0) fprintf(stderr, "%d\t%d\t%u\t%u\t%d\n",
+		       (int)rb_gc_count(),
+		       (int)objspace->rgengc.need_major_gc,
+		       (unsigned int)objspace->rgengc.oldmalloc_increase,
+		       (unsigned int)objspace->rgengc.oldmalloc_increase_limit,
+		       (unsigned int)gc_params.oldmalloc_limit_max);
+    }
+    else {
+	/* major GC */
+	objspace->rgengc.oldmalloc_increase = 0;
+
+	if ((objspace->profile.latest_gc_info & GPR_FLAG_MAJOR_BY_OLDMALLOC) == 0) {
+	    objspace->rgengc.oldmalloc_increase_limit =
+	      (size_t)(objspace->rgengc.oldmalloc_increase_limit / ((gc_params.oldmalloc_limit_growth_factor - 1)/10 + 1));
+	    if (objspace->rgengc.oldmalloc_increase_limit < gc_params.oldmalloc_limit_min) {
+		objspace->rgengc.oldmalloc_increase_limit = gc_params.oldmalloc_limit_min;
+	    }
+	}
+    }
+#endif
+}
+
+static int
+garbage_collect(rb_objspace_t *objspace, int full_mark, int immediate_mark, int immediate_sweep, int reason)
+{
+#if GC_PROFILE_MORE_DETAIL
+    objspace->profile.prepare_time = getrusage_time();
+#endif
+
+    gc_rest(objspace);
+
+#if GC_PROFILE_MORE_DETAIL
+    objspace->profile.prepare_time = getrusage_time() - objspace->profile.prepare_time;
+#endif
+
+    return gc_start(objspace, full_mark, immediate_mark, immediate_sweep, reason);
+}
+
+static int
+gc_start(rb_objspace_t *objspace, const int full_mark, const int immediate_mark, const unsigned int immediate_sweep, int reason)
+{
+    int do_full_mark = full_mark;
+    objspace->flags.immediate_sweep = immediate_sweep;
+
+    if (!heap_allocated_pages) return FALSE;      /* heap is not ready */
+    if (!ready_to_gc(objspace)) return TRUE; /* GC is not allowed */
+
+    if (RGENGC_CHECK_MODE) {
+	assert(objspace->flags.stat == gc_stat_none);
+	assert(!is_lazy_sweeping(heap_eden));
+	assert(!is_incremental_marking(objspace));
+#if RGENGC_CHECK_MODE >= 2
+	gc_verify_internal_consistency(Qnil);
+#endif
+    }
+
+    gc_enter(objspace, "gc_start");
+
+    if (ruby_gc_stressful) {
+	int flag = FIXNUM_P(ruby_gc_stress_mode) ? FIX2INT(ruby_gc_stress_mode) : 0;
+
+	if ((flag & (1<<gc_stress_no_major)) == 0) {
+	    do_full_mark = TRUE;
+	}
+
+	objspace->flags.immediate_sweep = !(flag & (1<<gc_stress_no_immediate_sweep));
+    }
+    else {
+#if USE_RGENGC
+	if (objspace->rgengc.need_major_gc) {
+	    reason |= objspace->rgengc.need_major_gc;
+	    do_full_mark = TRUE;
+	}
+	else if (RGENGC_FORCE_MAJOR_GC) {
+	    reason = GPR_FLAG_MAJOR_BY_FORCE;
+	    do_full_mark = TRUE;
+	}
+
+	objspace->rgengc.need_major_gc = GPR_FLAG_NONE;
+#endif
+    }
+
+    if (do_full_mark && (reason & GPR_FLAG_MAJOR_MASK) == 0) {
+	reason |= GPR_FLAG_MAJOR_BY_FORCE; /* GC by CAPI, METHOD, and so on. */
+    }
+
+#if GC_ENABLE_INCREMENTAL_MARK
+    if (!GC_ENABLE_INCREMENTAL_MARK || objspace->flags.dont_incremental || immediate_mark) {
+	objspace->flags.during_incremental_marking = FALSE;
+    }
+    else {
+	objspace->flags.during_incremental_marking = do_full_mark;
+    }
+#endif
+
+    if (!GC_ENABLE_LAZY_SWEEP || objspace->flags.dont_incremental) {
+	objspace->flags.immediate_sweep = TRUE;
+    }
+
+    if (objspace->flags.immediate_sweep) reason |= GPR_FLAG_IMMEDIATE_SWEEP;
+
+    gc_report(1, objspace, "gc_start(%d, %d, %d, reason: %d) => %d, %d, %d\n",
+	      full_mark, immediate_mark, immediate_sweep, reason,
+	      do_full_mark, !is_incremental_marking(objspace), objspace->flags.immediate_sweep);
+
+    objspace->profile.count++;
+    objspace->profile.latest_gc_info = reason;
+    objspace->profile.total_allocated_objects_at_gc_start = objspace->total_allocated_objects;
+    objspace->profile.heap_used_at_gc_start = heap_allocated_pages;
+    gc_prof_setup_new_record(objspace, reason);
+    gc_reset_malloc_info(objspace);
+
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_GC_START, 0 /* TODO: pass minor/immediate flag? */);
+    if (RGENGC_CHECK_MODE) assert(during_gc);
+
+    gc_prof_timer_start(objspace);
+    {
+	gc_marks(objspace, do_full_mark);
+    }
+    gc_prof_timer_stop(objspace);
+
+    gc_exit(objspace, "gc_start");
+    return TRUE;
+}
+
+static void
+gc_rest(rb_objspace_t *objspace)
+{
+    int marking = is_incremental_marking(objspace);
+    int sweeping = is_lazy_sweeping(heap_eden);
+
+    if (marking || sweeping) {
+	gc_enter(objspace, "gc_rest");
+
+	if (RGENGC_CHECK_MODE >= 2) gc_verify_internal_consistency(Qnil);
+
+	if (is_incremental_marking(objspace)) {
+	    PUSH_MARK_FUNC_DATA(NULL);
+	    gc_marks_rest(objspace);
+	    POP_MARK_FUNC_DATA();
+	}
+	if (is_lazy_sweeping(heap_eden)) {
+	    gc_sweep_rest(objspace);
+	}
+	gc_exit(objspace, "gc_rest");
+    }
+}
+
+struct objspace_and_reason {
+    rb_objspace_t *objspace;
+    int reason;
+    int full_mark;
+    int immediate_mark;
+    int immediate_sweep;
+};
+
+static void
+gc_current_status_fill(rb_objspace_t *objspace, char *buff)
+{
+    int i = 0;
+    if (is_marking(objspace)) {
+	buff[i++] = 'M';
+#if USE_RGENGC
+	if (is_full_marking(objspace))        buff[i++] = 'F';
+#if GC_ENABLE_INCREMENTAL_MARK
+	if (is_incremental_marking(objspace)) buff[i++] = 'I';
+#endif
+#endif
+    }
+    else if (is_sweeping(objspace)) {
+	buff[i++] = 'S';
+	if (is_lazy_sweeping(heap_eden))      buff[i++] = 'L';
+    }
+    else {
+	buff[i++] = 'N';
+    }
+    buff[i] = '\0';
+}
+
+static const char *
+gc_current_status(rb_objspace_t *objspace)
+{
+    static char buff[0x10];
+    gc_current_status_fill(objspace, buff);
+    return buff;
+}
+
+#if PRINT_ENTER_EXIT_TICK
+
+static tick_t last_exit_tick;
+static tick_t enter_tick;
+static int enter_count = 0;
+static char last_gc_status[0x10];
+
+static inline void
+gc_record(rb_objspace_t *objspace, int direction, const char *event)
+{
+    if (direction == 0) { /* enter */
+	enter_count++;
+	enter_tick = tick();
+	gc_current_status_fill(objspace, last_gc_status);
+    }
+    else { /* exit */
+	tick_t exit_tick = tick();
+	char current_gc_status[0x10];
+	gc_current_status_fill(objspace, current_gc_status);
+#if 1
+	/* [last mutator time] [gc time] [event] */
+	fprintf(stderr, "%"PRItick"\t%"PRItick"\t%s\t[%s->%s|%c]\n",
+		enter_tick - last_exit_tick,
+		exit_tick - enter_tick,
+		event,
+		last_gc_status, current_gc_status,
+		(objspace->profile.latest_gc_info & GPR_FLAG_MAJOR_MASK) ? '+' : '-');
+	last_exit_tick = exit_tick;
+#else
+	/* [enter_tick] [gc time] [event] */
+	fprintf(stderr, "%"PRItick"\t%"PRItick"\t%s\t[%s->%s|%c]\n",
+		enter_tick,
+		exit_tick - enter_tick,
+		event,
+		last_gc_status, current_gc_status,
+		(objspace->profile.latest_gc_info & GPR_FLAG_MAJOR_MASK) ? '+' : '-');
+#endif
+    }
+}
+#else /* PRINT_ENTER_EXIT_TICK */
+static inline void
+gc_record(rb_objspace_t *objspace, int direction, const char *event)
+{
+    /* null */
+}
+#endif /* PRINT_ENTER_EXIT_TICK */
+
+static inline void
+gc_enter(rb_objspace_t *objspace, const char *event)
+{
+    if (RGENGC_CHECK_MODE) assert(during_gc == 0);
+    if (RGENGC_CHECK_MODE >= 3) gc_verify_internal_consistency(Qnil);
+
+    during_gc = TRUE;
+    gc_report(1, objspace, "gc_entr: %s [%s]\n", event, gc_current_status(objspace));
+    gc_record(objspace, 0, event);
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_GC_ENTER, 0); /* TODO: which parameter should be passed? */
+}
+
+static inline void
+gc_exit(rb_objspace_t *objspace, const char *event)
+{
+    if (RGENGC_CHECK_MODE) assert(during_gc != 0);
+
+    gc_event_hook(objspace, RUBY_INTERNAL_EVENT_GC_EXIT, 0); /* TODO: which parameter should be passsed? */
+    gc_record(objspace, 1, event);
+    gc_report(1, objspace, "gc_exit: %s [%s]\n", event, gc_current_status(objspace));
+    during_gc = FALSE;
+}
+
+static void *
+gc_with_gvl(void *ptr)
+{
+    struct objspace_and_reason *oar = (struct objspace_and_reason *)ptr;
+    return (void *)(VALUE)garbage_collect(oar->objspace, oar->full_mark, oar->immediate_mark, oar->immediate_sweep, oar->reason);
+}
+
+static int
+garbage_collect_with_gvl(rb_objspace_t *objspace, int full_mark, int immediate_mark, int immediate_sweep, int reason)
+{
+    if (dont_gc) return TRUE;
+    if (ruby_thread_has_gvl_p()) {
+	return garbage_collect(objspace, full_mark, immediate_mark, immediate_sweep, reason);
+    }
+    else {
+	if (ruby_native_thread_p()) {
+	    struct objspace_and_reason oar;
+	    oar.objspace = objspace;
+	    oar.reason = reason;
+	    oar.full_mark = full_mark;
+	    oar.immediate_mark = immediate_mark;
+	    oar.immediate_sweep = immediate_sweep;
+	    return (int)(VALUE)rb_thread_call_with_gvl(gc_with_gvl, (void *)&oar);
+	}
+	else {
+	    /* no ruby thread */
+	    fprintf(stderr, "[FATAL] failed to allocate memory\n");
+	    exit(EXIT_FAILURE);
+	}
+    }
+}
+
+int
+rb_garbage_collect(void)
+{
+    return garbage_collect(&rb_objspace, TRUE, TRUE, TRUE, GPR_FLAG_CAPI);
+}
+
+#undef Init_stack
+
+void
+Init_stack(volatile VALUE *addr)
+{
+    ruby_init_stack(addr);
+}
+
+/*
+ *  call-seq:
+ *     GC.start                     -> nil
+ *     GC.garbage_collect           -> nil
+ *     GC.start(full_mark: true, immediate_sweep: true)           -> nil
+ *     GC.garbage_collect(full_mark: true, immediate_sweep: true) -> nil
+ *
+ *  Initiates garbage collection, unless manually disabled.
+ *
+ *  This method is defined with keyword arguments that default to true:
+ *
+ *     def GC.start(full_mark: true, immediate_sweep: true); end
+ *
+ *  Use full_mark: false to perform a minor GC.
+ *  Use immediate_sweep: false to defer sweeping (use lazy sweep).
+ *
+ *  Note: These keyword arguments are implementation and version dependent. They
+ *  are not guaranteed to be future-compatible, and may be ignored if the
+ *  underlying implementation does not support them.
+ */
+
+static VALUE
+gc_start_internal(int argc, VALUE *argv, VALUE self)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    int full_mark = TRUE, immediate_mark = TRUE, immediate_sweep = TRUE;
+    VALUE opt = Qnil;
+    static ID keyword_ids[3];
+
+    rb_scan_args(argc, argv, "0:", &opt);
+
+    if (!NIL_P(opt)) {
+	VALUE kwvals[3];
+
+	if (!keyword_ids[0]) {
+	    keyword_ids[0] = rb_intern("full_mark");
+	    keyword_ids[1] = rb_intern("immediate_mark");
+	    keyword_ids[2] = rb_intern("immediate_sweep");
+	}
+
+	rb_get_kwargs(opt, keyword_ids, 0, 3, kwvals);
+
+	if (kwvals[0] != Qundef) full_mark = RTEST(kwvals[0]);
+	if (kwvals[1] != Qundef) immediate_mark = RTEST(kwvals[1]);
+	if (kwvals[2] != Qundef) immediate_sweep = RTEST(kwvals[2]);
+    }
+
+    garbage_collect(objspace, full_mark, immediate_mark, immediate_sweep, GPR_FLAG_METHOD);
+    if (!finalizing) finalize_deferred(objspace);
+
+    return Qnil;
+}
+
+VALUE
+rb_gc_start(void)
+{
+    rb_gc();
+    return Qnil;
+}
+
+void
+rb_gc(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    garbage_collect(objspace, TRUE, TRUE, TRUE, GPR_FLAG_CAPI);
+    if (!finalizing) finalize_deferred(objspace);
+}
+
+int
+rb_during_gc(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    return during_gc;
+}
+
+#if RGENGC_PROFILE >= 2
+
+static const char *type_name(int type, VALUE obj);
+
+static void
+gc_count_add_each_types(VALUE hash, const char *name, const size_t *types)
+{
+    VALUE result = rb_hash_new();
+    int i;
+    for (i=0; i<T_MASK; i++) {
+	const char *type = type_name(i, 0);
+	rb_hash_aset(result, ID2SYM(rb_intern(type)), SIZET2NUM(types[i]));
+    }
+    rb_hash_aset(hash, ID2SYM(rb_intern(name)), result);
+}
+#endif
+
+size_t
+rb_gc_count(void)
+{
+    return rb_objspace.profile.count;
+}
+
+/*
+ *  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 SIZET2NUM(rb_gc_count());
+}
+
+static VALUE
+gc_info_decode(rb_objspace_t *objspace, const VALUE hash_or_key, const int orig_flags)
+{
+    static VALUE sym_major_by = Qnil, sym_gc_by, sym_immediate_sweep, sym_have_finalizer, sym_state;
+    static VALUE sym_nofree, sym_oldgen, sym_shady, sym_force, sym_stress;
+#if RGENGC_ESTIMATE_OLDMALLOC
+    static VALUE sym_oldmalloc;
+#endif
+    static VALUE sym_newobj, sym_malloc, sym_method, sym_capi;
+    static VALUE sym_none, sym_marking, sym_sweeping;
+    VALUE hash = Qnil, key = Qnil;
+    VALUE major_by;
+    VALUE flags = orig_flags ? orig_flags : objspace->profile.latest_gc_info;
+
+    if (SYMBOL_P(hash_or_key)) {
+	key = hash_or_key;
+    }
+    else if (RB_TYPE_P(hash_or_key, T_HASH)) {
+	hash = hash_or_key;
+    }
+    else {
+	rb_raise(rb_eTypeError, "non-hash or symbol given");
+    }
+
+    if (sym_major_by == Qnil) {
+#define S(s) sym_##s = ID2SYM(rb_intern_const(#s))
+	S(major_by);
+	S(gc_by);
+	S(immediate_sweep);
+	S(have_finalizer);
+	S(state);
+
+	S(stress);
+	S(nofree);
+	S(oldgen);
+	S(shady);
+	S(force);
+#if RGENGC_ESTIMATE_OLDMALLOC
+	S(oldmalloc);
+#endif
+	S(newobj);
+	S(malloc);
+	S(method);
+	S(capi);
+
+	S(none);
+	S(marking);
+	S(sweeping);
+#undef S
+    }
+
+#define SET(name, attr) \
+    if (key == sym_##name) \
+	return (attr); \
+    else if (hash != Qnil) \
+	rb_hash_aset(hash, sym_##name, (attr));
+
+    major_by =
+      (flags & GPR_FLAG_MAJOR_BY_NOFREE) ? sym_nofree :
+      (flags & GPR_FLAG_MAJOR_BY_OLDGEN) ? sym_oldgen :
+      (flags & GPR_FLAG_MAJOR_BY_SHADY)  ? sym_shady :
+      (flags & GPR_FLAG_MAJOR_BY_FORCE)  ? sym_force :
+#if RGENGC_ESTIMATE_OLDMALLOC
+      (flags & GPR_FLAG_MAJOR_BY_OLDMALLOC) ? sym_oldmalloc :
+#endif
+      Qnil;
+    SET(major_by, major_by);
+
+    SET(gc_by,
+	(flags & GPR_FLAG_NEWOBJ) ? sym_newobj :
+	(flags & GPR_FLAG_MALLOC) ? sym_malloc :
+	(flags & GPR_FLAG_METHOD) ? sym_method :
+	(flags & GPR_FLAG_CAPI)   ? sym_capi :
+	(flags & GPR_FLAG_STRESS) ? sym_stress :
+	Qnil
+    );
+
+    SET(have_finalizer, (flags & GPR_FLAG_HAVE_FINALIZE) ? Qtrue : Qfalse);
+    SET(immediate_sweep, (flags & GPR_FLAG_IMMEDIATE_SWEEP) ? Qtrue : Qfalse);
+
+    if (orig_flags == 0) {
+	SET(state, objspace->flags.stat == gc_stat_none ? sym_none :
+	           objspace->flags.stat == gc_stat_marking ? sym_marking : sym_sweeping);
+    }
+#undef SET
+
+    if (!NIL_P(key)) {/* matched key should return above */
+	rb_raise(rb_eArgError, "unknown key: %"PRIsVALUE, rb_sym2str(key));
+    }
+
+    return hash;
+}
+
+VALUE
+rb_gc_latest_gc_info(VALUE key)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    return gc_info_decode(objspace, key, 0);
+}
+
+/*
+ *  call-seq:
+ *     GC.latest_gc_info -> {:gc_by=>:newobj}
+ *     GC.latest_gc_info(hash) -> hash
+ *     GC.latest_gc_info(:major_by) -> :malloc
+ *
+ *  Returns information about the most recent garbage collection.
+ */
+
+static VALUE
+gc_latest_gc_info(int argc, VALUE *argv, VALUE self)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE arg = Qnil;
+
+    if (rb_scan_args(argc, argv, "01", &arg) == 1) {
+	if (!SYMBOL_P(arg) && !RB_TYPE_P(arg, T_HASH)) {
+	    rb_raise(rb_eTypeError, "non-hash or symbol given");
+	}
+    }
+
+    if (arg == Qnil) {
+	arg = rb_hash_new();
+    }
+
+    return gc_info_decode(objspace, arg, 0);
+}
+
+enum gc_stat_sym {
+    gc_stat_sym_count,
+    gc_stat_sym_heap_allocated_pages,
+    gc_stat_sym_heap_sorted_length,
+    gc_stat_sym_heap_allocatable_pages,
+    gc_stat_sym_heap_available_slots,
+    gc_stat_sym_heap_live_slots,
+    gc_stat_sym_heap_free_slots,
+    gc_stat_sym_heap_final_slots,
+    gc_stat_sym_heap_marked_slots,
+    gc_stat_sym_heap_swept_slots,
+    gc_stat_sym_heap_eden_pages,
+    gc_stat_sym_heap_tomb_pages,
+    gc_stat_sym_total_allocated_pages,
+    gc_stat_sym_total_freed_pages,
+    gc_stat_sym_total_allocated_objects,
+    gc_stat_sym_total_freed_objects,
+    gc_stat_sym_malloc_increase_bytes,
+    gc_stat_sym_malloc_increase_bytes_limit,
+#if USE_RGENGC
+    gc_stat_sym_minor_gc_count,
+    gc_stat_sym_major_gc_count,
+    gc_stat_sym_remembered_wb_unprotected_objects,
+    gc_stat_sym_remembered_wb_unprotected_objects_limit,
+    gc_stat_sym_old_objects,
+    gc_stat_sym_old_objects_limit,
+#if RGENGC_ESTIMATE_OLDMALLOC
+    gc_stat_sym_oldmalloc_increase_bytes,
+    gc_stat_sym_oldmalloc_increase_bytes_limit,
+#endif
+#if RGENGC_PROFILE
+    gc_stat_sym_total_generated_normal_object_count,
+    gc_stat_sym_total_generated_shady_object_count,
+    gc_stat_sym_total_shade_operation_count,
+    gc_stat_sym_total_promoted_count,
+    gc_stat_sym_total_remembered_normal_object_count,
+    gc_stat_sym_total_remembered_shady_object_count,
+#endif
+#endif
+    gc_stat_sym_last
+};
+
+enum gc_stat_compat_sym {
+    gc_stat_compat_sym_gc_stat_heap_used,
+    gc_stat_compat_sym_heap_eden_page_length,
+    gc_stat_compat_sym_heap_tomb_page_length,
+    gc_stat_compat_sym_heap_increment,
+    gc_stat_compat_sym_heap_length,
+    gc_stat_compat_sym_heap_live_slot,
+    gc_stat_compat_sym_heap_free_slot,
+    gc_stat_compat_sym_heap_final_slot,
+    gc_stat_compat_sym_heap_swept_slot,
+#if USE_RGENGC
+    gc_stat_compat_sym_remembered_shady_object,
+    gc_stat_compat_sym_remembered_shady_object_limit,
+    gc_stat_compat_sym_old_object,
+    gc_stat_compat_sym_old_object_limit,
+#endif
+    gc_stat_compat_sym_total_allocated_object,
+    gc_stat_compat_sym_total_freed_object,
+    gc_stat_compat_sym_malloc_increase,
+    gc_stat_compat_sym_malloc_limit,
+#if RGENGC_ESTIMATE_OLDMALLOC
+    gc_stat_compat_sym_oldmalloc_increase,
+    gc_stat_compat_sym_oldmalloc_limit,
+#endif
+    gc_stat_compat_sym_last
+};
+
+static VALUE gc_stat_symbols[gc_stat_sym_last];
+static VALUE gc_stat_compat_symbols[gc_stat_compat_sym_last];
+static VALUE gc_stat_compat_table;
+
+static void
+setup_gc_stat_symbols(void)
+{
+    if (gc_stat_symbols[0] == 0) {
+#define S(s) gc_stat_symbols[gc_stat_sym_##s] = ID2SYM(rb_intern_const(#s))
+	S(count);
+	S(heap_allocated_pages);
+	S(heap_sorted_length);
+	S(heap_allocatable_pages);
+	S(heap_available_slots);
+	S(heap_live_slots);
+	S(heap_free_slots);
+	S(heap_final_slots);
+	S(heap_marked_slots);
+	S(heap_swept_slots);
+	S(heap_eden_pages);
+	S(heap_tomb_pages);
+	S(total_allocated_pages);
+	S(total_freed_pages);
+	S(total_allocated_objects);
+	S(total_freed_objects);
+	S(malloc_increase_bytes);
+	S(malloc_increase_bytes_limit);
+#if USE_RGENGC
+	S(minor_gc_count);
+	S(major_gc_count);
+	S(remembered_wb_unprotected_objects);
+	S(remembered_wb_unprotected_objects_limit);
+	S(old_objects);
+	S(old_objects_limit);
+#if RGENGC_ESTIMATE_OLDMALLOC
+	S(oldmalloc_increase_bytes);
+	S(oldmalloc_increase_bytes_limit);
+#endif
+#if RGENGC_PROFILE
+	S(total_generated_normal_object_count);
+	S(total_generated_shady_object_count);
+	S(total_shade_operation_count);
+	S(total_promoted_count);
+	S(total_remembered_normal_object_count);
+	S(total_remembered_shady_object_count);
+#endif /* RGENGC_PROFILE */
+#endif /* USE_RGENGC */
+#undef S
+#define S(s) gc_stat_compat_symbols[gc_stat_compat_sym_##s] = ID2SYM(rb_intern_const(#s))
+	S(gc_stat_heap_used);
+	S(heap_eden_page_length);
+	S(heap_tomb_page_length);
+	S(heap_increment);
+	S(heap_length);
+	S(heap_live_slot);
+	S(heap_free_slot);
+	S(heap_final_slot);
+	S(heap_swept_slot);
+#if USE_RGEGC
+	S(remembered_shady_object);
+	S(remembered_shady_object_limit);
+	S(old_object);
+	S(old_object_limit);
+#endif
+	S(total_allocated_object);
+	S(total_freed_object);
+	S(malloc_increase);
+	S(malloc_limit);
+#if RGENGC_ESTIMATE_OLDMALLOC
+	S(oldmalloc_increase);
+	S(oldmalloc_limit);
+#endif
+#undef S
+
+	{
+	    VALUE table = gc_stat_compat_table = rb_hash_new();
+	    rb_obj_hide(table);
+	    rb_gc_register_mark_object(table);
+
+	    /* compatibility layer for Ruby 2.1 */
+#define OLD_SYM(s) gc_stat_compat_symbols[gc_stat_compat_sym_##s]
+#define NEW_SYM(s) gc_stat_symbols[gc_stat_sym_##s]
+	    rb_hash_aset(table, OLD_SYM(gc_stat_heap_used), NEW_SYM(heap_allocated_pages));
+	    rb_hash_aset(table, OLD_SYM(heap_eden_page_length), NEW_SYM(heap_eden_pages));
+	    rb_hash_aset(table, OLD_SYM(heap_tomb_page_length), NEW_SYM(heap_tomb_pages));
+	    rb_hash_aset(table, OLD_SYM(heap_increment), NEW_SYM(heap_allocatable_pages));
+	    rb_hash_aset(table, OLD_SYM(heap_length), NEW_SYM(heap_sorted_length));
+	    rb_hash_aset(table, OLD_SYM(heap_live_slot), NEW_SYM(heap_live_slots));
+	    rb_hash_aset(table, OLD_SYM(heap_free_slot), NEW_SYM(heap_free_slots));
+	    rb_hash_aset(table, OLD_SYM(heap_final_slot), NEW_SYM(heap_final_slots));
+	    rb_hash_aset(table, OLD_SYM(heap_swept_slot), NEW_SYM(heap_swept_slots));
+#if USE_RGEGC
+	    rb_hash_aset(table, OLD_SYM(remembered_shady_object), NEW_SYM(remembered_wb_unprotected_objects));
+	    rb_hash_aset(table, OLD_SYM(remembered_shady_object_limit), NEW_SYM(remembered_wb_unprotected_objects_limit));
+	    rb_hash_aset(table, OLD_SYM(old_object), NEW_SYM(old_objects));
+	    rb_hash_aset(table, OLD_SYM(old_object_limit), NEW_SYM(old_objects_limit));
+#endif
+	    rb_hash_aset(table, OLD_SYM(total_allocated_object), NEW_SYM(total_allocated_objects));
+	    rb_hash_aset(table, OLD_SYM(total_freed_object), NEW_SYM(total_freed_objects));
+	    rb_hash_aset(table, OLD_SYM(malloc_increase), NEW_SYM(malloc_increase_bytes));
+	    rb_hash_aset(table, OLD_SYM(malloc_limit), NEW_SYM(malloc_increase_bytes_limit));
+#if RGENGC_ESTIMATE_OLDMALLOC
+	    rb_hash_aset(table, OLD_SYM(oldmalloc_increase), NEW_SYM(oldmalloc_increase_bytes));
+	    rb_hash_aset(table, OLD_SYM(oldmalloc_limit), NEW_SYM(oldmalloc_increase_bytes_limit));
+#endif
+#undef OLD_SYM
+#undef NEW_SYM
+	    rb_obj_freeze(table);
+	}
+    }
+}
+
+static VALUE
+compat_key(VALUE key)
+{
+    VALUE new_key = rb_hash_lookup(gc_stat_compat_table, key);
+
+    if (!NIL_P(new_key)) {
+	static int warned = 0;
+	if (warned == 0) {
+	    rb_warn("GC.stat keys were changed from Ruby 2.1. "
+		    "In this case, you refer to obsolete `%"PRIsVALUE"' (new key is `%"PRIsVALUE"'). "
+		    "Please check <https://bugs.ruby-lang.org/issues/9924> for more information.",
+		    key, new_key);
+	    warned = 1;
+	}
+    }
+
+    return new_key;
+}
+
+static VALUE
+default_proc_for_compat_func(VALUE hash, VALUE dmy, int argc, VALUE *argv)
+{
+    VALUE key, new_key;
+
+    Check_Type(hash, T_HASH);
+    rb_check_arity(argc, 2, 2);
+    key = argv[1];
+
+    if ((new_key = compat_key(key)) != Qnil) {
+	return rb_hash_lookup(hash, new_key);
+    }
+
+    return Qnil;
+}
+
+size_t
+gc_stat_internal(VALUE hash_or_sym)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE hash = Qnil, key = Qnil;
+
+    setup_gc_stat_symbols();
+
+    if (RB_TYPE_P(hash_or_sym, T_HASH)) {
+	hash = hash_or_sym;
+
+	if (NIL_P(RHASH_IFNONE(hash))) {
+	    static VALUE default_proc_for_compat = 0;
+	    if (default_proc_for_compat == 0) { /* TODO: it should be */
+		default_proc_for_compat = rb_proc_new(default_proc_for_compat_func, Qnil);
+		rb_gc_register_mark_object(default_proc_for_compat);
+	    }
+	    rb_hash_set_default_proc(hash, default_proc_for_compat);
+	}
+    }
+    else if (SYMBOL_P(hash_or_sym)) {
+	key = hash_or_sym;
+    }
+    else {
+	rb_raise(rb_eTypeError, "non-hash or symbol argument");
+    }
+
+#define SET(name, attr) \
+    if (key == gc_stat_symbols[gc_stat_sym_##name]) \
+	return attr; \
+    else if (hash != Qnil) \
+	rb_hash_aset(hash, gc_stat_symbols[gc_stat_sym_##name], SIZET2NUM(attr));
+
+  again:
+    SET(count, objspace->profile.count);
+
+    /* implementation dependent counters */
+    SET(heap_allocated_pages, heap_allocated_pages);
+    SET(heap_sorted_length, heap_pages_sorted_length);
+    SET(heap_allocatable_pages, heap_allocatable_pages);
+    SET(heap_available_slots, objspace_available_slots(objspace));
+    SET(heap_live_slots, objspace_live_slots(objspace));
+    SET(heap_free_slots, objspace_free_slots(objspace));
+    SET(heap_final_slots, heap_pages_final_slots);
+    SET(heap_marked_slots, objspace->marked_slots);
+    SET(heap_swept_slots, heap_pages_swept_slots);
+    SET(heap_eden_pages, heap_eden->page_length);
+    SET(heap_tomb_pages, heap_tomb->page_length);
+    SET(total_allocated_pages, objspace->profile.total_allocated_pages);
+    SET(total_freed_pages, objspace->profile.total_freed_pages);
+    SET(total_allocated_objects, objspace->total_allocated_objects);
+    SET(total_freed_objects, objspace->profile.total_freed_objects);
+    SET(malloc_increase_bytes, malloc_increase);
+    SET(malloc_increase_bytes_limit, malloc_limit);
+#if USE_RGENGC
+    SET(minor_gc_count, objspace->profile.minor_gc_count);
+    SET(major_gc_count, objspace->profile.major_gc_count);
+    SET(remembered_wb_unprotected_objects, objspace->rgengc.remembered_wb_unprotected_objects);
+    SET(remembered_wb_unprotected_objects_limit, objspace->rgengc.remembered_wb_unprotected_objects_limit);
+    SET(old_objects, objspace->rgengc.old_objects);
+    SET(old_objects_limit, objspace->rgengc.old_objects_limit);
+#if RGENGC_ESTIMATE_OLDMALLOC
+    SET(oldmalloc_increase_bytes, objspace->rgengc.oldmalloc_increase);
+    SET(oldmalloc_increase_bytes_limit, objspace->rgengc.oldmalloc_increase_limit);
+#endif
+
+#if RGENGC_PROFILE
+    SET(total_generated_normal_object_count, objspace->profile.total_generated_normal_object_count);
+    SET(total_generated_shady_object_count, objspace->profile.total_generated_shady_object_count);
+    SET(total_shade_operation_count, objspace->profile.total_shade_operation_count);
+    SET(total_promoted_count, objspace->profile.total_promoted_count);
+    SET(total_remembered_normal_object_count, objspace->profile.total_remembered_normal_object_count);
+    SET(total_remembered_shady_object_count, objspace->profile.total_remembered_shady_object_count);
+#endif /* RGENGC_PROFILE */
+#endif /* USE_RGENGC */
+#undef SET
+
+    if (!NIL_P(key)) { /* matched key should return above */
+	VALUE new_key;
+	if ((new_key = compat_key(key)) != Qnil) {
+	    key = new_key;
+	    goto again;
+	}
+	rb_raise(rb_eArgError, "unknown key: %"PRIsVALUE, rb_sym2str(key));
+    }
+
+#if defined(RGENGC_PROFILE) && RGENGC_PROFILE >= 2
+    if (hash != Qnil) {
+	gc_count_add_each_types(hash, "generated_normal_object_count_types", objspace->profile.generated_normal_object_count_types);
+	gc_count_add_each_types(hash, "generated_shady_object_count_types", objspace->profile.generated_shady_object_count_types);
+	gc_count_add_each_types(hash, "shade_operation_count_types", objspace->profile.shade_operation_count_types);
+	gc_count_add_each_types(hash, "promoted_types", objspace->profile.promoted_types);
+	gc_count_add_each_types(hash, "remembered_normal_object_count_types", objspace->profile.remembered_normal_object_count_types);
+	gc_count_add_each_types(hash, "remembered_shady_object_count_types", objspace->profile.remembered_shady_object_count_types);
+    }
+#endif
+
+    return 0;
+}
+
+/*
+ *  call-seq:
+ *     GC.stat -> Hash
+ *     GC.stat(hash) -> hash
+ *     GC.stat(:key) -> Numeric
+ *
+ *  Returns a Hash containing information about the GC.
+ *
+ *  The hash includes information about internal statistics about GC such as:
+ *
+ *      {
+ *          :count=>0,
+ *          :heap_allocated_pages=>24,
+ *          :heap_sorted_length=>24,
+ *          :heap_allocatable_pages=>0,
+ *          :heap_available_slots=>9783,
+ *          :heap_live_slots=>7713,
+ *          :heap_free_slots=>2070,
+ *          :heap_final_slots=>0,
+ *          :heap_marked_slots=>0,
+ *          :heap_swept_slots=>0,
+ *          :heap_eden_pages=>24,
+ *          :heap_tomb_pages=>0,
+ *          :total_allocated_pages=>24,
+ *          :total_freed_pages=>0,
+ *          :total_allocated_objects=>7796,
+ *          :total_freed_objects=>83,
+ *          :malloc_increase_bytes=>2389312,
+ *          :malloc_increase_bytes_limit=>16777216,
+ *          :minor_gc_count=>0,
+ *          :major_gc_count=>0,
+ *          :remembered_wb_unprotected_objects=>0,
+ *          :remembered_wb_unprotected_objects_limit=>0,
+ *          :old_objects=>0,
+ *          :old_objects_limit=>0,
+ *          :oldmalloc_increase_bytes=>2389760,
+ *          :oldmalloc_increase_bytes_limit=>16777216
+ *      }
+ *
+ *  The contents of the hash are implementation specific and may be changed in
+ *  the future.
+ *
+ *  This method is only expected to work on C Ruby.
+ *
+ */
+
+static VALUE
+gc_stat(int argc, VALUE *argv, VALUE self)
+{
+    VALUE arg = Qnil;
+
+    if (rb_scan_args(argc, argv, "01", &arg) == 1) {
+	if (SYMBOL_P(arg)) {
+	    size_t value = gc_stat_internal(arg);
+	    return SIZET2NUM(value);
+	}
+	else if (!RB_TYPE_P(arg, T_HASH)) {
+	    rb_raise(rb_eTypeError, "non-hash or symbol given");
+	}
+    }
+
+    if (arg == Qnil) {
+        arg = rb_hash_new();
+    }
+    gc_stat_internal(arg);
+    return arg;
+}
+
+size_t
+rb_gc_stat(VALUE key)
+{
+    if (SYMBOL_P(key)) {
+	size_t value = gc_stat_internal(key);
+	return value;
+    }
+    else {
+	gc_stat_internal(key);
+	return 0;
+    }
+}
+
+/*
+ *  call-seq:
+ *    GC.stress	    -> fixnum, 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_mode;
+}
+
+static void
+gc_stress_set(rb_objspace_t *objspace, VALUE flag)
+{
+    objspace->flags.gc_stressful = RTEST(flag);
+    objspace->gc_stress_mode = flag;
+}
+
+/*
+ *  call-seq:
+ *    GC.stress = flag          -> flag
+ *
+ *  Updates the GC stress mode.
+ *
+ *  When stress mode is enabled, the GC is invoked at every GC opportunity:
+ *  all memory and object allocations.
+ *
+ *  Enabling stress mode will degrade performance, it is only for debugging.
+ *
+ *  flag can be true, false, or a fixnum bit-ORed following flags.
+ *    0x01:: no major GC
+ *    0x02:: no immediate sweep
+ *    0x04:: full mark after malloc/calloc/realloc
+ */
+
+static VALUE
+gc_stress_set_m(VALUE self, VALUE flag)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    rb_secure(2);
+    gc_stress_set(objspace, flag);
+    return flag;
+}
+
+/*
+ *  call-seq:
+ *     GC.enable    -> true or false
+ *
+ *  Enables garbage collection, returning +true+ if garbage
+ *  collection was previously disabled.
+ *
+ *     GC.disable   #=> false
+ *     GC.enable    #=> true
+ *     GC.enable    #=> false
+ *
+ */
+
+VALUE
+rb_gc_enable(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    int old = dont_gc;
+
+    dont_gc = FALSE;
+    return old ? Qtrue : Qfalse;
+}
+
+/*
+ *  call-seq:
+ *     GC.disable    -> true or false
+ *
+ *  Disables garbage collection, returning +true+ if garbage
+ *  collection was already disabled.
+ *
+ *     GC.disable   #=> false
+ *     GC.disable   #=> true
+ *
+ */
+
+VALUE
+rb_gc_disable(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    int old = dont_gc;
+
+    gc_rest(objspace);
+
+    dont_gc = TRUE;
+    return old ? Qtrue : Qfalse;
+}
+
+static int
+get_envparam_size(const char *name, size_t *default_value, size_t lower_bound)
+{
+    char *ptr = getenv(name);
+    ssize_t val;
+
+    if (ptr != NULL && *ptr) {
+	size_t unit = 0;
+	char *end;
+#if SIZEOF_SIZE_T == SIZEOF_LONG_LONG
+	val = strtoll(ptr, &end, 0);
+#else
+	val = strtol(ptr, &end, 0);
+#endif
+	switch (*end) {
+	  case 'k': case 'K':
+	    unit = 1024;
+	    ++end;
+	    break;
+	  case 'm': case 'M':
+	    unit = 1024*1024;
+	    ++end;
+	    break;
+	  case 'g': case 'G':
+	    unit = 1024*1024*1024;
+	    ++end;
+	    break;
+	}
+	while (*end && isspace((unsigned char)*end)) end++;
+	if (*end) {
+	    if (RTEST(ruby_verbose)) fprintf(stderr, "invalid string for %s: %s\n", name, ptr);
+	    return 0;
+	}
+	if (unit > 0) {
+	    if (val < -(ssize_t)(SIZE_MAX / 2 / unit) || (ssize_t)(SIZE_MAX / 2 / unit) < val) {
+		if (RTEST(ruby_verbose)) fprintf(stderr, "%s=%s is ignored because it overflows\n", name, ptr);
+		return 0;
+	    }
+	    val *= unit;
+	}
+	if (val > 0 && (size_t)val > lower_bound) {
+	    if (RTEST(ruby_verbose)) {
+		fprintf(stderr, "%s=%"PRIdSIZE" (default value: %"PRIdSIZE")\n", name, val, *default_value);
+	    }
+	    *default_value = (size_t)val;
+	    return 1;
+	}
+	else {
+	    if (RTEST(ruby_verbose)) {
+		fprintf(stderr, "%s=%"PRIdSIZE" (default value: %"PRIdSIZE") is ignored because it must be greater than %"PRIdSIZE".\n",
+			name, val, *default_value, lower_bound);
+	    }
+	    return 0;
+	}
+    }
+    return 0;
+}
+
+static int
+get_envparam_double(const char *name, double *default_value, double lower_bound)
+{
+    char *ptr = getenv(name);
+    double val;
+
+    if (ptr != NULL && *ptr) {
+	char *end;
+	val = strtod(ptr, &end);
+	if (!*ptr || *end) {
+	    if (RTEST(ruby_verbose)) fprintf(stderr, "invalid string for %s: %s\n", name, ptr);
+	    return 0;
+	}
+	if (val > lower_bound) {
+	    if (RTEST(ruby_verbose)) fprintf(stderr, "%s=%f (default value: %f)\n", name, val, *default_value);
+	    *default_value = val;
+	    return 1;
+	}
+	else {
+	    if (RTEST(ruby_verbose)) fprintf(stderr, "%s=%f (default value: %f) is ignored because it must be greater than %f.\n", name, val, *default_value, lower_bound);
+	}
+    }
+    return 0;
+}
+
+static void
+gc_set_initial_pages(void)
+{
+    size_t min_pages;
+    rb_objspace_t *objspace = &rb_objspace;
+
+    min_pages = gc_params.heap_init_slots / HEAP_OBJ_LIMIT;
+    if (min_pages > heap_eden->page_length) {
+	heap_add_pages(objspace, heap_eden, min_pages - heap_eden->page_length);
+    }
+}
+
+/*
+ * GC tuning environment variables
+ *
+ * * RUBY_GC_HEAP_INIT_SLOTS
+ *   - Initial allocation slots.
+ * * RUBY_GC_HEAP_FREE_SLOTS
+ *   - Prepare at least this amount of slots after GC.
+ *   - Allocate slots if there are not enough slots.
+ * * RUBY_GC_HEAP_GROWTH_FACTOR (new from 2.1)
+ *   - Allocate slots by this factor.
+ *   - (next slots number) = (current slots number) * (this factor)
+ * * RUBY_GC_HEAP_GROWTH_MAX_SLOTS (new from 2.1)
+ *   - Allocation rate is limited to this number of slots.
+ * * RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR (new from 2.1.1)
+ *   - Do full GC when the number of old objects is more than R * N
+ *     where R is this factor and
+ *           N is the number of old objects just after last full GC.
+ *
+ *  * obsolete
+ *    * RUBY_FREE_MIN       -> RUBY_GC_HEAP_FREE_SLOTS (from 2.1)
+ *    * RUBY_HEAP_MIN_SLOTS -> RUBY_GC_HEAP_INIT_SLOTS (from 2.1)
+ *
+ * * RUBY_GC_MALLOC_LIMIT
+ * * RUBY_GC_MALLOC_LIMIT_MAX (new from 2.1)
+ * * RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR (new from 2.1)
+ *
+ * * RUBY_GC_OLDMALLOC_LIMIT (new from 2.1)
+ * * RUBY_GC_OLDMALLOC_LIMIT_MAX (new from 2.1)
+ * * RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR (new from 2.1)
+ */
+
+void
+ruby_gc_set_params(int safe_level)
+{
+    if (safe_level > 0) return;
+
+    /* RUBY_GC_HEAP_FREE_SLOTS */
+    if (get_envparam_size("RUBY_GC_HEAP_FREE_SLOTS", &gc_params.heap_free_slots, 0)) {
+	/* ok */
+    }
+    else if (get_envparam_size("RUBY_FREE_MIN", &gc_params.heap_free_slots, 0)) {
+	rb_warn("RUBY_FREE_MIN is obsolete. Use RUBY_GC_HEAP_FREE_SLOTS instead.");
+    }
+
+    /* RUBY_GC_HEAP_INIT_SLOTS */
+    if (get_envparam_size("RUBY_GC_HEAP_INIT_SLOTS", &gc_params.heap_init_slots, 0)) {
+	gc_set_initial_pages();
+    }
+    else if (get_envparam_size("RUBY_HEAP_MIN_SLOTS", &gc_params.heap_init_slots, 0)) {
+	rb_warn("RUBY_HEAP_MIN_SLOTS is obsolete. Use RUBY_GC_HEAP_INIT_SLOTS instead.");
+	gc_set_initial_pages();
+    }
+
+    get_envparam_double("RUBY_GC_HEAP_GROWTH_FACTOR", &gc_params.growth_factor, 1.0);
+    get_envparam_size  ("RUBY_GC_HEAP_GROWTH_MAX_SLOTS", &gc_params.growth_max_slots, 0);
+    get_envparam_double("RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR", &gc_params.oldobject_limit_factor, 0.0);
+
+    get_envparam_size  ("RUBY_GC_MALLOC_LIMIT", &gc_params.malloc_limit_min, 0);
+    get_envparam_size  ("RUBY_GC_MALLOC_LIMIT_MAX", &gc_params.malloc_limit_max, 0);
+    get_envparam_double("RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR", &gc_params.malloc_limit_growth_factor, 1.0);
+
+#if RGENGC_ESTIMATE_OLDMALLOC
+    if (get_envparam_size("RUBY_GC_OLDMALLOC_LIMIT", &gc_params.oldmalloc_limit_min, 0)) {
+	rb_objspace_t *objspace = &rb_objspace;
+	objspace->rgengc.oldmalloc_increase_limit = gc_params.oldmalloc_limit_min;
+    }
+    get_envparam_size  ("RUBY_GC_OLDMALLOC_LIMIT_MAX", &gc_params.oldmalloc_limit_max, 0);
+    get_envparam_double("RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR", &gc_params.oldmalloc_limit_growth_factor, 1.0);
+#endif
+}
+
+void
+rb_objspace_reachable_objects_from(VALUE obj, void (func)(VALUE, void *), void *data)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    if (is_markable_object(objspace, obj)) {
+	struct mark_func_data_struct mfd;
+	mfd.mark_func = func;
+	mfd.data = data;
+	PUSH_MARK_FUNC_DATA(&mfd);
+	gc_mark_children(objspace, obj);
+	POP_MARK_FUNC_DATA();
+    }
+}
+
+struct root_objects_data {
+    const char *category;
+    void (*func)(const char *category, VALUE, void *);
+    void *data;
+};
+
+static void
+root_objects_from(VALUE obj, void *ptr)
+{
+    const struct root_objects_data *data = (struct root_objects_data *)ptr;
+    (*data->func)(data->category, obj, data->data);
+}
+
+void
+rb_objspace_reachable_objects_from_root(void (func)(const char *category, VALUE, void *), void *passing_data)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    struct root_objects_data data;
+    struct mark_func_data_struct mfd;
+
+    data.func = func;
+    data.data = passing_data;
+
+    mfd.mark_func = root_objects_from;
+    mfd.data = &data;
+
+    PUSH_MARK_FUNC_DATA(&mfd);
+    gc_mark_roots(objspace, &data.category);
+    POP_MARK_FUNC_DATA();
+}
+
+/*
+  ------------------------ Extended allocator ------------------------
+*/
+
+static void objspace_xfree(rb_objspace_t *objspace, void *ptr, size_t size);
+
+static void *
+negative_size_allocation_error_with_gvl(void *ptr)
+{
+    rb_raise(rb_eNoMemError, "%s", (const char *)ptr);
+    return 0; /* should not be reached */
+}
+
+static void
+negative_size_allocation_error(const char *msg)
+{
+    if (ruby_thread_has_gvl_p()) {
+	rb_raise(rb_eNoMemError, "%s", msg);
+    }
+    else {
+	if (ruby_native_thread_p()) {
+	    rb_thread_call_with_gvl(negative_size_allocation_error_with_gvl, (void *)msg);
+	}
+	else {
+	    fprintf(stderr, "[FATAL] %s\n", msg);
+	    exit(EXIT_FAILURE);
+	}
+    }
+}
+
+static void *
+ruby_memerror_body(void *dummy)
+{
+    rb_memerror();
+    return 0;
+}
+
+static void
+ruby_memerror(void)
+{
+    if (ruby_thread_has_gvl_p()) {
+	rb_memerror();
+    }
+    else {
+	if (ruby_native_thread_p()) {
+	    rb_thread_call_with_gvl(ruby_memerror_body, 0);
+	}
+	else {
+	    /* no ruby thread */
+	    fprintf(stderr, "[FATAL] failed to allocate memory\n");
+	    exit(EXIT_FAILURE);
+	}
+    }
+}
+
+void
+rb_memerror(void)
+{
+    rb_thread_t *th = GET_THREAD();
+    rb_objspace_t *objspace = &rb_objspace;
+
+    if (during_gc) gc_exit(objspace, "rb_memerror");
+
+    if (!nomem_error ||
+	rb_thread_raised_p(th, RAISED_NOMEMORY)) {
+	fprintf(stderr, "[FATAL] failed to allocate memory\n");
+	exit(EXIT_FAILURE);
+    }
+    if (rb_thread_raised_p(th, RAISED_NOMEMORY)) {
+	rb_thread_raised_clear(th);
+	GET_THREAD()->errinfo = nomem_error;
+	JUMP_TAG(TAG_RAISE);
+    }
+    rb_thread_raised_set(th, RAISED_NOMEMORY);
+    rb_exc_raise(nomem_error);
+}
+
+static void *
+aligned_malloc(size_t alignment, size_t size)
+{
+    void *res;
+
+#if defined __MINGW32__
+    res = __mingw_aligned_malloc(size, alignment);
+#elif defined _WIN32 && !defined __CYGWIN__
+    void *_aligned_malloc(size_t, size_t);
+    res = _aligned_malloc(size, alignment);
+#elif defined(HAVE_POSIX_MEMALIGN)
+    if (posix_memalign(&res, alignment, size) == 0) {
+        return res;
+    }
+    else {
+        return NULL;
+    }
+#elif defined(HAVE_MEMALIGN)
+    res = memalign(alignment, size);
+#else
+    char* aligned;
+    res = malloc(alignment + size + sizeof(void*));
+    aligned = (char*)res + alignment + sizeof(void*);
+    aligned -= ((VALUE)aligned & (alignment - 1));
+    ((void**)aligned)[-1] = res;
+    res = (void*)aligned;
+#endif
+
+#if defined(_DEBUG) || GC_DEBUG
+    /* alignment must be a power of 2 */
+    assert(((alignment - 1) & alignment) == 0);
+    assert(alignment % sizeof(void*) == 0);
+#endif
+    return res;
+}
+
+static void
+aligned_free(void *ptr)
+{
+#if defined __MINGW32__
+    __mingw_aligned_free(ptr);
+#elif defined _WIN32 && !defined __CYGWIN__
+    _aligned_free(ptr);
+#elif defined(HAVE_MEMALIGN) || defined(HAVE_POSIX_MEMALIGN)
+    free(ptr);
+#else
+    free(((void**)ptr)[-1]);
+#endif
+}
+
+static inline size_t
+objspace_malloc_size(rb_objspace_t *objspace, void *ptr, size_t hint)
+{
+#ifdef HAVE_MALLOC_USABLE_SIZE
+    return malloc_usable_size(ptr);
+#else
+    return hint;
+#endif
+}
+
+enum memop_type {
+    MEMOP_TYPE_MALLOC  = 1,
+    MEMOP_TYPE_FREE    = 2,
+    MEMOP_TYPE_REALLOC = 3
+};
+
+static inline void
+atomic_sub_nounderflow(size_t *var, size_t sub)
+{
+    if (sub == 0) return;
+
+    while (1) {
+	size_t val = *var;
+	if (val < sub) sub = val;
+	if (ATOMIC_SIZE_CAS(*var, val, val-sub) == val) break;
+    }
+}
+
+static void
+objspace_malloc_gc_stress(rb_objspace_t *objspace)
+{
+    if (ruby_gc_stressful && ruby_native_thread_p()) {
+	garbage_collect_with_gvl(objspace, gc_stress_full_mark_after_malloc_p(), TRUE, TRUE, GPR_FLAG_STRESS | GPR_FLAG_MALLOC);
+    }
+}
+
+static void
+objspace_malloc_increase(rb_objspace_t *objspace, void *mem, size_t new_size, size_t old_size, enum memop_type type)
+{
+    if (new_size > old_size) {
+	ATOMIC_SIZE_ADD(malloc_increase, new_size - old_size);
+#if RGENGC_ESTIMATE_OLDMALLOC
+	ATOMIC_SIZE_ADD(objspace->rgengc.oldmalloc_increase, new_size - old_size);
+#endif
+    }
+    else {
+	atomic_sub_nounderflow(&malloc_increase, old_size - new_size);
+#if RGENGC_ESTIMATE_OLDMALLOC
+	atomic_sub_nounderflow(&objspace->rgengc.oldmalloc_increase, old_size - new_size);
+#endif
+    }
+
+    if (type == MEMOP_TYPE_MALLOC) {
+      retry:
+	if (malloc_increase > malloc_limit && ruby_native_thread_p() && !dont_gc) {
+	    if (ruby_thread_has_gvl_p() && is_lazy_sweeping(heap_eden)) {
+		gc_rest(objspace); /* gc_rest can reduce malloc_increase */
+		goto retry;
+	    }
+	    garbage_collect_with_gvl(objspace, FALSE, FALSE, FALSE, GPR_FLAG_MALLOC);
+	}
+    }
+
+#if MALLOC_ALLOCATED_SIZE
+    if (new_size >= old_size) {
+	ATOMIC_SIZE_ADD(objspace->malloc_params.allocated_size, new_size - old_size);
+    }
+    else {
+	size_t dec_size = old_size - new_size;
+	size_t allocated_size = objspace->malloc_params.allocated_size;
+
+#if MALLOC_ALLOCATED_SIZE_CHECK
+	if (allocated_size < dec_size) {
+	    rb_bug("objspace_malloc_increase: underflow malloc_params.allocated_size.");
+	}
+#endif
+	atomic_sub_nounderflow(&objspace->malloc_params.allocated_size, dec_size);
+    }
+
+    if (0) fprintf(stderr, "increase - ptr: %p, type: %s, new_size: %d, old_size: %d\n",
+		   mem,
+		   type == MEMOP_TYPE_MALLOC  ? "malloc" :
+		   type == MEMOP_TYPE_FREE    ? "free  " :
+		   type == MEMOP_TYPE_REALLOC ? "realloc": "error",
+		   (int)new_size, (int)old_size);
+
+    switch (type) {
+      case MEMOP_TYPE_MALLOC:
+	ATOMIC_SIZE_INC(objspace->malloc_params.allocations);
+	break;
+      case MEMOP_TYPE_FREE:
+	{
+	    size_t allocations = objspace->malloc_params.allocations;
+	    if (allocations > 0) {
+		atomic_sub_nounderflow(&objspace->malloc_params.allocations, 1);
+	    }
+#if MALLOC_ALLOCATED_SIZE_CHECK
+	    else {
+		if (RGENGC_CHECK_MODE) assert(objspace->malloc_params.allocations > 0);
+	    }
+#endif
+	}
+	break;
+      case MEMOP_TYPE_REALLOC: /* ignore */ break;
+    }
+#endif
+}
+
+static inline size_t
+objspace_malloc_prepare(rb_objspace_t *objspace, size_t size)
+{
+    if ((ssize_t)size < 0) {
+	negative_size_allocation_error("negative allocation size (or too big)");
+    }
+    if (size == 0) size = 1;
+
+#if CALC_EXACT_MALLOC_SIZE
+    size += sizeof(size_t);
+#endif
+
+    return size;
+}
+
+static inline void *
+objspace_malloc_fixup(rb_objspace_t *objspace, void *mem, size_t size)
+{
+#if CALC_EXACT_MALLOC_SIZE
+    ((size_t *)mem)[0] = size;
+    mem = (size_t *)mem + 1;
+#endif
+
+    return mem;
+}
+
+#define TRY_WITH_GC(alloc) do { \
+        objspace_malloc_gc_stress(objspace); \
+	if (!(alloc) && \
+	    (!garbage_collect_with_gvl(objspace, TRUE, TRUE, TRUE, GPR_FLAG_MALLOC) || /* full/immediate mark && immediate sweep */ \
+	     !(alloc))) { \
+	    ruby_memerror(); \
+	} \
+    } while (0)
+
+static void *
+objspace_xmalloc(rb_objspace_t *objspace, size_t size)
+{
+    void *mem;
+
+    size = objspace_malloc_prepare(objspace, size);
+    TRY_WITH_GC(mem = malloc(size));
+    size = objspace_malloc_size(objspace, mem, size);
+    objspace_malloc_increase(objspace, mem, size, 0, MEMOP_TYPE_MALLOC);
+    return objspace_malloc_fixup(objspace, mem, size);
+}
+
+static void *
+objspace_xrealloc(rb_objspace_t *objspace, void *ptr, size_t new_size, size_t old_size)
+{
+    void *mem;
+
+    if ((ssize_t)new_size < 0) {
+	negative_size_allocation_error("negative re-allocation size");
+    }
+
+    if (!ptr) return objspace_xmalloc(objspace, new_size);
+
+    /*
+     * The behavior of realloc(ptr, 0) is implementation defined.
+     * Therefore we don't use realloc(ptr, 0) for portability reason.
+     * see http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_400.htm
+     */
+    if (new_size == 0) {
+	objspace_xfree(objspace, ptr, old_size);
+	return 0;
+    }
+
+#if CALC_EXACT_MALLOC_SIZE
+    new_size += sizeof(size_t);
+    ptr = (size_t *)ptr - 1;
+    old_size = ((size_t *)ptr)[0];
+#endif
+
+    old_size = objspace_malloc_size(objspace, ptr, old_size);
+    TRY_WITH_GC(mem = realloc(ptr, new_size));
+    new_size = objspace_malloc_size(objspace, mem, new_size);
+
+#if CALC_EXACT_MALLOC_SIZE
+    ((size_t *)mem)[0] = new_size;
+    mem = (size_t *)mem + 1;
+#endif
+
+    objspace_malloc_increase(objspace, mem, new_size, old_size, MEMOP_TYPE_REALLOC);
+
+    return mem;
+}
+
+static void
+objspace_xfree(rb_objspace_t *objspace, void *ptr, size_t old_size)
+{
+#if CALC_EXACT_MALLOC_SIZE
+    ptr = ((size_t *)ptr) - 1;
+    old_size = ((size_t*)ptr)[0];
+#endif
+    old_size = objspace_malloc_size(objspace, ptr, old_size);
+
+    free(ptr);
+
+    objspace_malloc_increase(objspace, ptr, 0, old_size, MEMOP_TYPE_FREE);
+}
+
+void *
+ruby_xmalloc(size_t size)
+{
+    return objspace_xmalloc(&rb_objspace, size);
+}
+
+static inline size_t
+xmalloc2_size(size_t n, size_t size)
+{
+    size_t len = size * n;
+    if (n != 0 && size != len / n) {
+	rb_raise(rb_eArgError, "malloc: possible integer overflow");
+    }
+    return len;
+}
+
+void *
+ruby_xmalloc2(size_t n, size_t size)
+{
+    return objspace_xmalloc(&rb_objspace, xmalloc2_size(n, size));
+}
+
+static void *
+objspace_xcalloc(rb_objspace_t *objspace, size_t count, size_t elsize)
+{
+    void *mem;
+    size_t size;
+
+    size = xmalloc2_size(count, elsize);
+    size = objspace_malloc_prepare(objspace, size);
+
+    TRY_WITH_GC(mem = calloc(1, size));
+    size = objspace_malloc_size(objspace, mem, size);
+    objspace_malloc_increase(objspace, mem, size, 0, MEMOP_TYPE_MALLOC);
+    return objspace_malloc_fixup(objspace, mem, size);
+}
+
+void *
+ruby_xcalloc(size_t n, size_t size)
+{
+    return objspace_xcalloc(&rb_objspace, n, size);
+}
+
+#ifdef ruby_sized_xrealloc
+#undef ruby_sized_xrealloc
+#endif
+void *
+ruby_sized_xrealloc(void *ptr, size_t new_size, size_t old_size)
+{
+    return objspace_xrealloc(&rb_objspace, ptr, new_size, old_size);
+}
+
+void *
+ruby_xrealloc(void *ptr, size_t new_size)
+{
+    return ruby_sized_xrealloc(ptr, new_size, 0);
+}
+
+#ifdef ruby_sized_xrealloc2
+#undef ruby_sized_xrealloc2
+#endif
+void *
+ruby_sized_xrealloc2(void *ptr, size_t n, size_t size, size_t old_n)
+{
+    size_t len = size * n;
+    if (n != 0 && size != len / n) {
+	rb_raise(rb_eArgError, "realloc: possible integer overflow");
+    }
+    return objspace_xrealloc(&rb_objspace, ptr, len, old_n * size);
+}
+
+void *
+ruby_xrealloc2(void *ptr, size_t n, size_t size)
+{
+    return ruby_sized_xrealloc2(ptr, n, size, 0);
+}
+
+#ifdef ruby_sized_xfree
+#undef ruby_sized_xfree
+#endif
+void
+ruby_sized_xfree(void *x, size_t size)
+{
+    if (x) {
+	objspace_xfree(&rb_objspace, x, size);
+    }
+}
+
+void
+ruby_xfree(void *x)
+{
+    ruby_sized_xfree(x, 0);
+}
+
+/* Mimic ruby_xmalloc, but need not rb_objspace.
+ * should return pointer suitable for ruby_xfree
+ */
+void *
+ruby_mimmalloc(size_t size)
+{
+    void *mem;
+#if CALC_EXACT_MALLOC_SIZE
+    size += sizeof(size_t);
+#endif
+    mem = malloc(size);
+#if CALC_EXACT_MALLOC_SIZE
+    /* set 0 for consistency of allocated_size/allocations */
+    ((size_t *)mem)[0] = 0;
+    mem = (size_t *)mem + 1;
+#endif
+    return mem;
+}
+
+void
+ruby_mimfree(void *ptr)
+{
+    size_t *mem = (size_t *)ptr;
+#if CALC_EXACT_MALLOC_SIZE
+    mem = mem - 1;
+#endif
+    free(mem);
+}
+
+#if MALLOC_ALLOCATED_SIZE
+/*
+ *  call-seq:
+ *     GC.malloc_allocated_size -> Integer
+ *
+ *  Returns the size of memory allocated by malloc().
+ *
+ *  Only available if ruby was built with +CALC_EXACT_MALLOC_SIZE+.
+ */
+
+static VALUE
+gc_malloc_allocated_size(VALUE self)
+{
+    return UINT2NUM(rb_objspace.malloc_params.allocated_size);
+}
+
+/*
+ *  call-seq:
+ *     GC.malloc_allocations -> Integer
+ *
+ *  Returns the number of malloc() allocations.
+ *
+ *  Only available if ruby was built with +CALC_EXACT_MALLOC_SIZE+.
+ */
+
+static VALUE
+gc_malloc_allocations(VALUE self)
+{
+    return UINT2NUM(rb_objspace.malloc_params.allocations);
+}
+#endif
+
+/*
+  ------------------------------ WeakMap ------------------------------
+*/
+
+struct weakmap {
+    st_table *obj2wmap;		/* obj -> [ref,...] */
+    st_table *wmap2obj;		/* ref -> obj */
+    VALUE final;
+};
+
+#define WMAP_DELETE_DEAD_OBJECT_IN_MARK 0
+
+#if WMAP_DELETE_DEAD_OBJECT_IN_MARK
+static int
+wmap_mark_map(st_data_t key, st_data_t val, st_data_t arg)
+{
+    rb_objspace_t *objspace = (rb_objspace_t *)arg;
+    VALUE obj = (VALUE)val;
+    if (!is_live_object(objspace, obj)) return ST_DELETE;
+    return ST_CONTINUE;
+}
+#endif
+
+static void
+wmap_mark(void *ptr)
+{
+    struct weakmap *w = ptr;
+#if WMAP_DELETE_DEAD_OBJECT_IN_MARK
+    if (w->obj2wmap) st_foreach(w->obj2wmap, wmap_mark_map, (st_data_t)&rb_objspace);
+#endif
+    rb_gc_mark(w->final);
+}
+
+static int
+wmap_free_map(st_data_t key, st_data_t val, st_data_t arg)
+{
+    VALUE *ptr = (VALUE *)val;
+    ruby_sized_xfree(ptr, (ptr[0] + 1) * sizeof(VALUE));
+    return ST_CONTINUE;
+}
+
+static void
+wmap_free(void *ptr)
+{
+    struct weakmap *w = ptr;
+    st_foreach(w->obj2wmap, wmap_free_map, 0);
+    st_free_table(w->obj2wmap);
+    st_free_table(w->wmap2obj);
+}
+
+static int
+wmap_memsize_map(st_data_t key, st_data_t val, st_data_t arg)
+{
+    VALUE *ptr = (VALUE *)val;
+    *(size_t *)arg += (ptr[0] + 1) * sizeof(VALUE);
+    return ST_CONTINUE;
+}
+
+static size_t
+wmap_memsize(const void *ptr)
+{
+    size_t size;
+    const struct weakmap *w = ptr;
+    if (!w) return 0;
+    size = sizeof(*w);
+    size += st_memsize(w->obj2wmap);
+    size += st_memsize(w->wmap2obj);
+    st_foreach(w->obj2wmap, wmap_memsize_map, (st_data_t)&size);
+    return size;
+}
+
+static const rb_data_type_t weakmap_type = {
+    "weakmap",
+    {
+	wmap_mark,
+	wmap_free,
+	wmap_memsize,
+    },
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+static VALUE
+wmap_allocate(VALUE klass)
+{
+    struct weakmap *w;
+    VALUE obj = TypedData_Make_Struct(klass, struct weakmap, &weakmap_type, w);
+    w->obj2wmap = st_init_numtable();
+    w->wmap2obj = st_init_numtable();
+    w->final = rb_obj_method(obj, ID2SYM(rb_intern("finalize")));
+    return obj;
+}
+
+static int
+wmap_final_func(st_data_t *key, st_data_t *value, st_data_t arg, int existing)
+{
+    VALUE wmap, *ptr, size, i, j;
+    if (!existing) return ST_STOP;
+    wmap = (VALUE)arg, ptr = (VALUE *)*value;
+    for (i = j = 1, size = ptr[0]; i <= size; ++i) {
+	if (ptr[i] != wmap) {
+	    ptr[j++] = ptr[i];
+	}
+    }
+    if (j == 1) {
+	ruby_sized_xfree(ptr, i * sizeof(VALUE));
+	return ST_DELETE;
+    }
+    if (j < i) {
+	ptr = ruby_sized_xrealloc2(ptr, j + 1, sizeof(VALUE), i);
+	ptr[0] = j;
+	*value = (st_data_t)ptr;
+    }
+    return ST_CONTINUE;
+}
+
+static VALUE
+wmap_finalize(VALUE self, VALUE objid)
+{
+    st_data_t orig, wmap, data;
+    VALUE obj, *rids, i, size;
+    struct weakmap *w;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    /* Get reference from object id. */
+    obj = obj_id_to_ref(objid);
+
+    /* obj is original referenced object and/or weak reference. */
+    orig = (st_data_t)obj;
+    if (st_delete(w->obj2wmap, &orig, &data)) {
+	rids = (VALUE *)data;
+	size = *rids++;
+	for (i = 0; i < size; ++i) {
+	    wmap = (st_data_t)rids[i];
+	    st_delete(w->wmap2obj, &wmap, NULL);
+	}
+	ruby_sized_xfree((VALUE *)data, (size + 1) * sizeof(VALUE));
+    }
+
+    wmap = (st_data_t)obj;
+    if (st_delete(w->wmap2obj, &wmap, &orig)) {
+	wmap = (st_data_t)obj;
+	st_update(w->obj2wmap, orig, wmap_final_func, wmap);
+    }
+    return self;
+}
+
+struct wmap_iter_arg {
+    rb_objspace_t *objspace;
+    VALUE value;
+};
+
+static int
+wmap_inspect_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    VALUE str = (VALUE)arg;
+    VALUE k = (VALUE)key, v = (VALUE)val;
+
+    if (RSTRING_PTR(str)[0] == '#') {
+	rb_str_cat2(str, ", ");
+    }
+    else {
+	rb_str_cat2(str, ": ");
+	RSTRING_PTR(str)[0] = '#';
+    }
+    k = SPECIAL_CONST_P(k) ? rb_inspect(k) : rb_any_to_s(k);
+    rb_str_append(str, k);
+    rb_str_cat2(str, " => ");
+    v = SPECIAL_CONST_P(v) ? rb_inspect(v) : rb_any_to_s(v);
+    rb_str_append(str, v);
+    OBJ_INFECT(str, k);
+    OBJ_INFECT(str, v);
+
+    return ST_CONTINUE;
+}
+
+static VALUE
+wmap_inspect(VALUE self)
+{
+    VALUE str;
+    VALUE c = rb_class_name(CLASS_OF(self));
+    struct weakmap *w;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    str = rb_sprintf("-<%"PRIsVALUE":%p", c, (void *)self);
+    if (w->wmap2obj) {
+	st_foreach(w->wmap2obj, wmap_inspect_i, str);
+    }
+    RSTRING_PTR(str)[0] = '#';
+    rb_str_cat2(str, ">");
+    return str;
+}
+
+static int
+wmap_each_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    rb_objspace_t *objspace = (rb_objspace_t *)arg;
+    VALUE obj = (VALUE)val;
+    if (is_id_value(objspace, obj) && is_live_object(objspace, obj)) {
+	rb_yield_values(2, (VALUE)key, obj);
+    }
+    return ST_CONTINUE;
+}
+
+/* Iterates over keys and objects in a weakly referenced object */
+static VALUE
+wmap_each(VALUE self)
+{
+    struct weakmap *w;
+    rb_objspace_t *objspace = &rb_objspace;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    st_foreach(w->wmap2obj, wmap_each_i, (st_data_t)objspace);
+    return self;
+}
+
+static int
+wmap_each_key_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    rb_objspace_t *objspace = (rb_objspace_t *)arg;
+    VALUE obj = (VALUE)val;
+    if (is_id_value(objspace, obj) && is_live_object(objspace, obj)) {
+	rb_yield((VALUE)key);
+    }
+    return ST_CONTINUE;
+}
+
+/* Iterates over keys and objects in a weakly referenced object */
+static VALUE
+wmap_each_key(VALUE self)
+{
+    struct weakmap *w;
+    rb_objspace_t *objspace = &rb_objspace;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    st_foreach(w->wmap2obj, wmap_each_key_i, (st_data_t)objspace);
+    return self;
+}
+
+static int
+wmap_each_value_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    rb_objspace_t *objspace = (rb_objspace_t *)arg;
+    VALUE obj = (VALUE)val;
+    if (is_id_value(objspace, obj) && is_live_object(objspace, obj)) {
+	rb_yield(obj);
+    }
+    return ST_CONTINUE;
+}
+
+/* Iterates over keys and objects in a weakly referenced object */
+static VALUE
+wmap_each_value(VALUE self)
+{
+    struct weakmap *w;
+    rb_objspace_t *objspace = &rb_objspace;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    st_foreach(w->wmap2obj, wmap_each_value_i, (st_data_t)objspace);
+    return self;
+}
+
+static int
+wmap_keys_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    struct wmap_iter_arg *argp = (struct wmap_iter_arg *)arg;
+    rb_objspace_t *objspace = argp->objspace;
+    VALUE ary = argp->value;
+    VALUE obj = (VALUE)val;
+    if (is_id_value(objspace, obj) && is_live_object(objspace, obj)) {
+	rb_ary_push(ary, (VALUE)key);
+    }
+    return ST_CONTINUE;
+}
+
+/* Iterates over keys and objects in a weakly referenced object */
+static VALUE
+wmap_keys(VALUE self)
+{
+    struct weakmap *w;
+    struct wmap_iter_arg args;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    args.objspace = &rb_objspace;
+    args.value = rb_ary_new();
+    st_foreach(w->wmap2obj, wmap_keys_i, (st_data_t)&args);
+    return args.value;
+}
+
+static int
+wmap_values_i(st_data_t key, st_data_t val, st_data_t arg)
+{
+    struct wmap_iter_arg *argp = (struct wmap_iter_arg *)arg;
+    rb_objspace_t *objspace = argp->objspace;
+    VALUE ary = argp->value;
+    VALUE obj = (VALUE)val;
+    if (is_id_value(objspace, obj) && is_live_object(objspace, obj)) {
+	rb_ary_push(ary, obj);
+    }
+    return ST_CONTINUE;
+}
+
+/* Iterates over values and objects in a weakly referenced object */
+static VALUE
+wmap_values(VALUE self)
+{
+    struct weakmap *w;
+    struct wmap_iter_arg args;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    args.objspace = &rb_objspace;
+    args.value = rb_ary_new();
+    st_foreach(w->wmap2obj, wmap_values_i, (st_data_t)&args);
+    return args.value;
+}
+
+static int
+wmap_aset_update(st_data_t *key, st_data_t *val, st_data_t arg, int existing)
+{
+    VALUE size, *ptr, *optr;
+    if (existing) {
+	size = (ptr = optr = (VALUE *)*val)[0];
+	++size;
+	ptr = ruby_sized_xrealloc2(ptr, size + 1, sizeof(VALUE), size);
+    }
+    else {
+	optr = 0;
+	size = 1;
+	ptr = ruby_xmalloc2(2, sizeof(VALUE));
+    }
+    ptr[0] = size;
+    ptr[size] = (VALUE)arg;
+    if (ptr == optr) return ST_STOP;
+    *val = (st_data_t)ptr;
+    return ST_CONTINUE;
+}
+
+/* Creates a weak reference from the given key to the given value */
+static VALUE
+wmap_aset(VALUE self, VALUE wmap, VALUE orig)
+{
+    struct weakmap *w;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    should_be_finalizable(orig);
+    should_be_finalizable(wmap);
+    define_final0(orig, w->final);
+    define_final0(wmap, w->final);
+    st_update(w->obj2wmap, (st_data_t)orig, wmap_aset_update, wmap);
+    st_insert(w->wmap2obj, (st_data_t)wmap, (st_data_t)orig);
+    return nonspecial_obj_id(orig);
+}
+
+/* Retrieves a weakly referenced object with the given key */
+static VALUE
+wmap_aref(VALUE self, VALUE wmap)
+{
+    st_data_t data;
+    VALUE obj;
+    struct weakmap *w;
+    rb_objspace_t *objspace = &rb_objspace;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    if (!st_lookup(w->wmap2obj, (st_data_t)wmap, &data)) return Qnil;
+    obj = (VALUE)data;
+    if (!is_id_value(objspace, obj)) return Qnil;
+    if (!is_live_object(objspace, obj)) return Qnil;
+    return obj;
+}
+
+/* Returns +true+ if +key+ is registered */
+static VALUE
+wmap_has_key(VALUE self, VALUE key)
+{
+    return NIL_P(wmap_aref(self, key)) ? Qfalse : Qtrue;
+}
+
+static VALUE
+wmap_size(VALUE self)
+{
+    struct weakmap *w;
+    st_index_t n;
+
+    TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
+    n = w->wmap2obj->num_entries;
+#if SIZEOF_ST_INDEX_T <= SIZEOF_LONG
+    return ULONG2NUM(n);
+#else
+    return ULL2NUM(n);
+#endif
+}
+
+/*
+  ------------------------------ GC profiler ------------------------------
+*/
+
+#define GC_PROFILE_RECORD_DEFAULT_SIZE 100
+
+/* return sec in user time */
+static double
+getrusage_time(void)
+{
+#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_PROCESS_CPUTIME_ID)
+    {
+        static int try_clock_gettime = 1;
+        struct timespec ts;
+        if (try_clock_gettime && clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == 0) {
+            return ts.tv_sec + ts.tv_nsec * 1e-9;
+        }
+        else {
+            try_clock_gettime = 0;
+        }
+    }
+#endif
+
+#ifdef RUSAGE_SELF
+    {
+        struct rusage usage;
+        struct timeval time;
+        if (getrusage(RUSAGE_SELF, &usage) == 0) {
+            time = usage.ru_utime;
+            return time.tv_sec + time.tv_usec * 1e-6;
+        }
+    }
+#endif
+
+#ifdef _WIN32
+    {
+	FILETIME creation_time, exit_time, kernel_time, user_time;
+	ULARGE_INTEGER ui;
+	LONG_LONG q;
+	double t;
+
+	if (GetProcessTimes(GetCurrentProcess(),
+			    &creation_time, &exit_time, &kernel_time, &user_time) != 0) {
+	    memcpy(&ui, &user_time, sizeof(FILETIME));
+	    q = ui.QuadPart / 10L;
+	    t = (DWORD)(q % 1000000L) * 1e-6;
+	    q /= 1000000L;
+#ifdef __GNUC__
+	    t += q;
+#else
+	    t += (double)(DWORD)(q >> 16) * (1 << 16);
+	    t += (DWORD)q & ~(~0 << 16);
+#endif
+	    return t;
+	}
+    }
+#endif
+
+    return 0.0;
+}
+
+static inline void
+gc_prof_setup_new_record(rb_objspace_t *objspace, int reason)
+{
+    if (objspace->profile.run) {
+	size_t index = objspace->profile.next_index;
+	gc_profile_record *record;
+
+	/* create new record */
+	objspace->profile.next_index++;
+
+	if (!objspace->profile.records) {
+	    objspace->profile.size = GC_PROFILE_RECORD_DEFAULT_SIZE;
+	    objspace->profile.records = malloc(sizeof(gc_profile_record) * objspace->profile.size);
+	}
+	if (index >= objspace->profile.size) {
+	    objspace->profile.size += 1000;
+	    objspace->profile.records = realloc(objspace->profile.records, sizeof(gc_profile_record) * objspace->profile.size);
+	}
+	if (!objspace->profile.records) {
+	    rb_bug("gc_profile malloc or realloc miss");
+	}
+	record = objspace->profile.current_record = &objspace->profile.records[objspace->profile.next_index - 1];
+	MEMZERO(record, gc_profile_record, 1);
+
+	/* setup before-GC parameter */
+	record->flags = reason | (ruby_gc_stressful ? GPR_FLAG_STRESS : 0);
+#if MALLOC_ALLOCATED_SIZE
+	record->allocated_size = malloc_allocated_size;
+#endif
+#if GC_PROFILE_DETAIL_MEMORY
+#ifdef RUSAGE_SELF
+	{
+	    struct rusage usage;
+	    if (getrusage(RUSAGE_SELF, &usage) == 0) {
+		record->maxrss = usage.ru_maxrss;
+		record->minflt = usage.ru_minflt;
+		record->majflt = usage.ru_majflt;
+	    }
+	}
+#endif
+#endif
+    }
+}
+
+static inline void
+gc_prof_timer_start(rb_objspace_t *objspace)
+{
+    if (gc_prof_enabled(objspace)) {
+	gc_profile_record *record = gc_prof_record(objspace);
+#if GC_PROFILE_MORE_DETAIL
+	record->prepare_time = objspace->profile.prepare_time;
+#endif
+	record->gc_time = 0;
+	record->gc_invoke_time = getrusage_time();
+    }
+}
+
+static double
+elapsed_time_from(double time)
+{
+    double now = getrusage_time();
+    if (now > time) {
+	return now - time;
+    }
+    else {
+	return 0;
+    }
+}
+
+static inline void
+gc_prof_timer_stop(rb_objspace_t *objspace)
+{
+    if (gc_prof_enabled(objspace)) {
+	gc_profile_record *record = gc_prof_record(objspace);
+	record->gc_time = elapsed_time_from(record->gc_invoke_time);
+	record->gc_invoke_time -= objspace->profile.invoke_time;
+    }
+}
+
+static inline void
+gc_prof_mark_timer_start(rb_objspace_t *objspace)
+{
+    if (RUBY_DTRACE_GC_MARK_BEGIN_ENABLED()) {
+	RUBY_DTRACE_GC_MARK_BEGIN();
+    }
+#if GC_PROFILE_MORE_DETAIL
+    if (gc_prof_enabled(objspace)) {
+	gc_prof_record(objspace)->gc_mark_time = getrusage_time();
+    }
+#endif
+}
+
+static inline void
+gc_prof_mark_timer_stop(rb_objspace_t *objspace)
+{
+    if (RUBY_DTRACE_GC_MARK_END_ENABLED()) {
+	RUBY_DTRACE_GC_MARK_END();
+    }
+#if GC_PROFILE_MORE_DETAIL
+    if (gc_prof_enabled(objspace)) {
+        gc_profile_record *record = gc_prof_record(objspace);
+	record->gc_mark_time = elapsed_time_from(record->gc_mark_time);
+    }
+#endif
+}
+
+static inline void
+gc_prof_sweep_timer_start(rb_objspace_t *objspace)
+{
+    if (RUBY_DTRACE_GC_SWEEP_BEGIN_ENABLED()) {
+	RUBY_DTRACE_GC_SWEEP_BEGIN();
+    }
+    if (gc_prof_enabled(objspace)) {
+	gc_profile_record *record = gc_prof_record(objspace);
+
+	if (record->gc_time > 0 || GC_PROFILE_MORE_DETAIL) {
+	    objspace->profile.gc_sweep_start_time = getrusage_time();
+	}
+    }
+}
+
+static inline void
+gc_prof_sweep_timer_stop(rb_objspace_t *objspace)
+{
+    if (RUBY_DTRACE_GC_SWEEP_END_ENABLED()) {
+	RUBY_DTRACE_GC_SWEEP_END();
+    }
+
+    if (gc_prof_enabled(objspace)) {
+	double sweep_time;
+	gc_profile_record *record = gc_prof_record(objspace);
+
+	if (record->gc_time > 0) {
+	    sweep_time = elapsed_time_from(objspace->profile.gc_sweep_start_time);
+	    /* need to accumulate GC time for lazy sweep after gc() */
+	    record->gc_time += sweep_time;
+	}
+	else if (GC_PROFILE_MORE_DETAIL) {
+	    sweep_time = elapsed_time_from(objspace->profile.gc_sweep_start_time);
+	}
+
+#if GC_PROFILE_MORE_DETAIL
+	record->gc_sweep_time += sweep_time;
+	if (heap_pages_deferred_final) record->flags |= GPR_FLAG_HAVE_FINALIZE;
+#endif
+	if (heap_pages_deferred_final) objspace->profile.latest_gc_info |= GPR_FLAG_HAVE_FINALIZE;
+    }
+}
+
+static inline void
+gc_prof_set_malloc_info(rb_objspace_t *objspace)
+{
+#if GC_PROFILE_MORE_DETAIL
+    if (gc_prof_enabled(objspace)) {
+        gc_profile_record *record = gc_prof_record(objspace);
+	record->allocate_increase = malloc_increase;
+	record->allocate_limit = malloc_limit;
+    }
+#endif
+}
+
+static inline void
+gc_prof_set_heap_info(rb_objspace_t *objspace)
+{
+    if (gc_prof_enabled(objspace)) {
+	gc_profile_record *record = gc_prof_record(objspace);
+	size_t live = objspace->profile.total_allocated_objects_at_gc_start - objspace->profile.total_freed_objects;
+	size_t total = objspace->profile.heap_used_at_gc_start * HEAP_OBJ_LIMIT;
+
+#if GC_PROFILE_MORE_DETAIL
+	record->heap_use_pages = objspace->profile.heap_used_at_gc_start;
+	record->heap_live_objects = live;
+	record->heap_free_objects = total - live;
+#endif
+
+	record->heap_total_objects = total;
+	record->heap_use_size = live * sizeof(RVALUE);
+	record->heap_total_size = total * sizeof(RVALUE);
+    }
+}
+
+/*
+ *  call-seq:
+ *    GC::Profiler.clear          -> nil
+ *
+ *  Clears the GC profiler data.
+ *
+ */
+
+static VALUE
+gc_profile_clear(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    if (GC_PROFILE_RECORD_DEFAULT_SIZE * 2 < objspace->profile.size) {
+        objspace->profile.size = GC_PROFILE_RECORD_DEFAULT_SIZE * 2;
+        objspace->profile.records = realloc(objspace->profile.records, sizeof(gc_profile_record) * objspace->profile.size);
+        if (!objspace->profile.records) {
+            rb_memerror();
+        }
+    }
+    MEMZERO(objspace->profile.records, gc_profile_record, objspace->profile.size);
+    objspace->profile.next_index = 0;
+    objspace->profile.current_record = 0;
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *     GC::Profiler.raw_data	-> [Hash, ...]
+ *
+ *  Returns an Array of individual raw profile data Hashes ordered
+ *  from earliest to latest by +:GC_INVOKE_TIME+.
+ *
+ *  For example:
+ *
+ *    [
+ *	{
+ *	   :GC_TIME=>1.3000000000000858e-05,
+ *	   :GC_INVOKE_TIME=>0.010634999999999999,
+ *	   :HEAP_USE_SIZE=>289640,
+ *	   :HEAP_TOTAL_SIZE=>588960,
+ *	   :HEAP_TOTAL_OBJECTS=>14724,
+ *	   :GC_IS_MARKED=>false
+ *	},
+ *      # ...
+ *    ]
+ *
+ *  The keys mean:
+ *
+ *  +:GC_TIME+::
+ *	Time elapsed in seconds for this GC run
+ *  +:GC_INVOKE_TIME+::
+ *	Time elapsed in seconds from startup to when the GC was invoked
+ *  +:HEAP_USE_SIZE+::
+ *	Total bytes of heap used
+ *  +:HEAP_TOTAL_SIZE+::
+ *	Total size of heap in bytes
+ *  +:HEAP_TOTAL_OBJECTS+::
+ *	Total number of objects
+ *  +:GC_IS_MARKED+::
+ *	Returns +true+ if the GC is in mark phase
+ *
+ *  If ruby was built with +GC_PROFILE_MORE_DETAIL+, you will also have access
+ *  to the following hash keys:
+ *
+ *  +:GC_MARK_TIME+::
+ *  +:GC_SWEEP_TIME+::
+ *  +:ALLOCATE_INCREASE+::
+ *  +:ALLOCATE_LIMIT+::
+ *  +:HEAP_USE_PAGES+::
+ *  +:HEAP_LIVE_OBJECTS+::
+ *  +:HEAP_FREE_OBJECTS+::
+ *  +:HAVE_FINALIZE+::
+ *
+ */
+
+static VALUE
+gc_profile_record_get(void)
+{
+    VALUE prof;
+    VALUE gc_profile = rb_ary_new();
+    size_t i;
+    rb_objspace_t *objspace = (&rb_objspace);
+
+    if (!objspace->profile.run) {
+	return Qnil;
+    }
+
+    for (i =0; i < objspace->profile.next_index; i++) {
+	gc_profile_record *record = &objspace->profile.records[i];
+
+	prof = rb_hash_new();
+	rb_hash_aset(prof, ID2SYM(rb_intern("GC_FLAGS")), gc_info_decode(0, rb_hash_new(), record->flags));
+        rb_hash_aset(prof, ID2SYM(rb_intern("GC_TIME")), DBL2NUM(record->gc_time));
+        rb_hash_aset(prof, ID2SYM(rb_intern("GC_INVOKE_TIME")), DBL2NUM(record->gc_invoke_time));
+        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_USE_SIZE")), SIZET2NUM(record->heap_use_size));
+        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_TOTAL_SIZE")), SIZET2NUM(record->heap_total_size));
+        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_TOTAL_OBJECTS")), SIZET2NUM(record->heap_total_objects));
+        rb_hash_aset(prof, ID2SYM(rb_intern("GC_IS_MARKED")), Qtrue);
+#if GC_PROFILE_MORE_DETAIL
+        rb_hash_aset(prof, ID2SYM(rb_intern("GC_MARK_TIME")), DBL2NUM(record->gc_mark_time));
+        rb_hash_aset(prof, ID2SYM(rb_intern("GC_SWEEP_TIME")), DBL2NUM(record->gc_sweep_time));
+        rb_hash_aset(prof, ID2SYM(rb_intern("ALLOCATE_INCREASE")), SIZET2NUM(record->allocate_increase));
+        rb_hash_aset(prof, ID2SYM(rb_intern("ALLOCATE_LIMIT")), SIZET2NUM(record->allocate_limit));
+        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_USE_PAGES")), SIZET2NUM(record->heap_use_pages));
+        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_LIVE_OBJECTS")), SIZET2NUM(record->heap_live_objects));
+        rb_hash_aset(prof, ID2SYM(rb_intern("HEAP_FREE_OBJECTS")), SIZET2NUM(record->heap_free_objects));
+
+	rb_hash_aset(prof, ID2SYM(rb_intern("REMOVING_OBJECTS")), SIZET2NUM(record->removing_objects));
+	rb_hash_aset(prof, ID2SYM(rb_intern("EMPTY_OBJECTS")), SIZET2NUM(record->empty_objects));
+
+	rb_hash_aset(prof, ID2SYM(rb_intern("HAVE_FINALIZE")), (record->flags & GPR_FLAG_HAVE_FINALIZE) ? Qtrue : Qfalse);
+#endif
+
+#if RGENGC_PROFILE > 0
+	rb_hash_aset(prof, ID2SYM(rb_intern("OLD_OBJECTS")), SIZET2NUM(record->old_objects));
+	rb_hash_aset(prof, ID2SYM(rb_intern("REMEMBED_NORMAL_OBJECTS")), SIZET2NUM(record->remembered_normal_objects));
+	rb_hash_aset(prof, ID2SYM(rb_intern("REMEMBED_SHADY_OBJECTS")), SIZET2NUM(record->remembered_shady_objects));
+#endif
+	rb_ary_push(gc_profile, prof);
+    }
+
+    return gc_profile;
+}
+
+#if GC_PROFILE_MORE_DETAIL
+#define MAJOR_REASON_MAX 0x10
+
+static char *
+gc_profile_dump_major_reason(int flags, char *buff)
+{
+    int reason = flags & GPR_FLAG_MAJOR_MASK;
+    int i = 0;
+
+    if (reason == GPR_FLAG_NONE) {
+	buff[0] = '-';
+	buff[1] = 0;
+    }
+    else {
+#define C(x, s) \
+  if (reason & GPR_FLAG_MAJOR_BY_##x) { \
+      buff[i++] = #x[0]; \
+      if (i >= MAJOR_REASON_MAX) rb_bug("gc_profile_dump_major_reason: overflow"); \
+      buff[i] = 0; \
+  }
+	C(NOFREE, N);
+	C(OLDGEN, O);
+	C(SHADY,  S);
+	C(RESCAN, R);
+	C(STRESS, T);
+#if RGENGC_ESTIMATE_OLDMALLOC
+	C(OLDMALLOC, M);
+#endif
+#undef C
+    }
+    return buff;
+}
+#endif
+
+static void
+gc_profile_dump_on(VALUE out, VALUE (*append)(VALUE, VALUE))
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    size_t count = objspace->profile.next_index;
+#ifdef MAJOR_REASON_MAX
+    char reason_str[MAJOR_REASON_MAX];
+#endif
+
+    if (objspace->profile.run && count /* > 1 */) {
+	size_t i;
+	const gc_profile_record *record;
+
+	append(out, rb_sprintf("GC %"PRIuSIZE" invokes.\n", objspace->profile.count));
+	append(out, rb_str_new_cstr("Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC Time(ms)\n"));
+
+	for (i = 0; i < count; i++) {
+	    record = &objspace->profile.records[i];
+	    append(out, rb_sprintf("%5"PRIdSIZE" %19.3f %20"PRIuSIZE" %20"PRIuSIZE" %20"PRIuSIZE" %30.20f\n",
+				   i+1, record->gc_invoke_time, record->heap_use_size,
+				   record->heap_total_size, record->heap_total_objects, record->gc_time*1000));
+	}
+
+#if GC_PROFILE_MORE_DETAIL
+	append(out, rb_str_new_cstr("\n\n" \
+				    "More detail.\n" \
+				    "Prepare Time = Previously GC's rest sweep time\n"
+				    "Index Flags          Allocate Inc.  Allocate Limit"
+#if CALC_EXACT_MALLOC_SIZE
+				    "  Allocated Size"
+#endif
+				    "  Use Page     Mark Time(ms)    Sweep Time(ms)  Prepare Time(ms)  LivingObj    FreeObj RemovedObj   EmptyObj"
+#if RGENGC_PROFILE
+				    " OldgenObj RemNormObj RemShadObj"
+#endif
+#if GC_PROFILE_DETAIL_MEMORY
+				    " MaxRSS(KB) MinorFLT MajorFLT"
+#endif
+				    "\n"));
+
+	for (i = 0; i < count; i++) {
+	    record = &objspace->profile.records[i];
+	    append(out, rb_sprintf("%5"PRIdSIZE" %4s/%c/%6s%c %13"PRIuSIZE" %15"PRIuSIZE
+#if CALC_EXACT_MALLOC_SIZE
+				   " %15"PRIuSIZE
+#endif
+				   " %9"PRIuSIZE" %17.12f %17.12f %17.12f %10"PRIuSIZE" %10"PRIuSIZE" %10"PRIuSIZE" %10"PRIuSIZE
+#if RGENGC_PROFILE
+				   "%10"PRIuSIZE" %10"PRIuSIZE" %10"PRIuSIZE
+#endif
+#if GC_PROFILE_DETAIL_MEMORY
+				   "%11ld %8ld %8ld"
+#endif
+
+				   "\n",
+				   i+1,
+				   gc_profile_dump_major_reason(record->flags, reason_str),
+				   (record->flags & GPR_FLAG_HAVE_FINALIZE) ? 'F' : '.',
+				   (record->flags & GPR_FLAG_NEWOBJ) ? "NEWOBJ" :
+				   (record->flags & GPR_FLAG_MALLOC) ? "MALLOC" :
+				   (record->flags & GPR_FLAG_METHOD) ? "METHOD" :
+				   (record->flags & GPR_FLAG_CAPI)   ? "CAPI__" : "??????",
+				   (record->flags & GPR_FLAG_STRESS) ? '!' : ' ',
+				   record->allocate_increase, record->allocate_limit,
+#if CALC_EXACT_MALLOC_SIZE
+				   record->allocated_size,
+#endif
+				   record->heap_use_pages,
+				   record->gc_mark_time*1000,
+				   record->gc_sweep_time*1000,
+				   record->prepare_time*1000,
+
+				   record->heap_live_objects,
+				   record->heap_free_objects,
+				   record->removing_objects,
+				   record->empty_objects
+#if RGENGC_PROFILE
+				   ,
+				   record->old_objects,
+				   record->remembered_normal_objects,
+				   record->remembered_shady_objects
+#endif
+#if GC_PROFILE_DETAIL_MEMORY
+				   ,
+				   record->maxrss / 1024,
+				   record->minflt,
+				   record->majflt
+#endif
+
+		       ));
+	}
+#endif
+    }
+}
+
+/*
+ *  call-seq:
+ *     GC::Profiler.result  -> String
+ *
+ *  Returns a profile data report such as:
+ *
+ *    GC 1 invokes.
+ *    Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC time(ms)
+ *        1               0.012               159240               212940                10647         0.00000000000001530000
+ */
+
+static VALUE
+gc_profile_result(void)
+{
+	VALUE str = rb_str_buf_new(0);
+	gc_profile_dump_on(str, rb_str_buf_append);
+	return str;
+}
+
+/*
+ *  call-seq:
+ *     GC::Profiler.report
+ *     GC::Profiler.report(io)
+ *
+ *  Writes the GC::Profiler.result to <tt>$stdout</tt> or the given IO object.
+ *
+ */
+
+static VALUE
+gc_profile_report(int argc, VALUE *argv, VALUE self)
+{
+    VALUE out;
+
+    if (argc == 0) {
+	out = rb_stdout;
+    }
+    else {
+	rb_scan_args(argc, argv, "01", &out);
+    }
+    gc_profile_dump_on(out, rb_io_write);
+
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *     GC::Profiler.total_time	-> float
+ *
+ *  The total time used for garbage collection in seconds
+ */
+
+static VALUE
+gc_profile_total_time(VALUE self)
+{
+    double time = 0;
+    rb_objspace_t *objspace = &rb_objspace;
+
+    if (objspace->profile.run && objspace->profile.next_index > 0) {
+	size_t i;
+	size_t count = objspace->profile.next_index;
+
+	for (i = 0; i < count; i++) {
+	    time += objspace->profile.records[i].gc_time;
+	}
+    }
+    return DBL2NUM(time);
+}
+
+/*
+ *  call-seq:
+ *    GC::Profiler.enabled?	-> true or false
+ *
+ *  The current status of GC profile mode.
+ */
+
+static VALUE
+gc_profile_enable_get(VALUE self)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    return objspace->profile.run ? Qtrue : Qfalse;
+}
+
+/*
+ *  call-seq:
+ *    GC::Profiler.enable	-> nil
+ *
+ *  Starts the GC profiler.
+ *
+ */
+
+static VALUE
+gc_profile_enable(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    objspace->profile.run = TRUE;
+    objspace->profile.current_record = 0;
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *    GC::Profiler.disable	-> nil
+ *
+ *  Stops the GC profiler.
+ *
+ */
+
+static VALUE
+gc_profile_disable(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    objspace->profile.run = FALSE;
+    objspace->profile.current_record = 0;
+    return Qnil;
+}
+
+/*
+  ------------------------------ DEBUG ------------------------------
+*/
+
+static const char *
+type_name(int type, VALUE obj)
+{
+    switch (type) {
+#define TYPE_NAME(t) case (t): return #t;
+	    TYPE_NAME(T_NONE);
+	    TYPE_NAME(T_OBJECT);
+	    TYPE_NAME(T_CLASS);
+	    TYPE_NAME(T_MODULE);
+	    TYPE_NAME(T_FLOAT);
+	    TYPE_NAME(T_STRING);
+	    TYPE_NAME(T_REGEXP);
+	    TYPE_NAME(T_ARRAY);
+	    TYPE_NAME(T_HASH);
+	    TYPE_NAME(T_STRUCT);
+	    TYPE_NAME(T_BIGNUM);
+	    TYPE_NAME(T_FILE);
+	    TYPE_NAME(T_MATCH);
+	    TYPE_NAME(T_COMPLEX);
+	    TYPE_NAME(T_RATIONAL);
+	    TYPE_NAME(T_NIL);
+	    TYPE_NAME(T_TRUE);
+	    TYPE_NAME(T_FALSE);
+	    TYPE_NAME(T_SYMBOL);
+	    TYPE_NAME(T_FIXNUM);
+	    TYPE_NAME(T_UNDEF);
+	    TYPE_NAME(T_NODE);
+	    TYPE_NAME(T_ICLASS);
+	    TYPE_NAME(T_ZOMBIE);
+      case T_DATA:
+	if (obj && rb_objspace_data_type_name(obj)) {
+	    return rb_objspace_data_type_name(obj);
+	}
+	return "T_DATA";
+#undef TYPE_NAME
+    }
+    return "unknown";
+}
+
+static const char *
+obj_type_name(VALUE obj)
+{
+    return type_name(TYPE(obj), obj);
+}
+
+#if RGENGC_DEBUG || RGENGC_CHECK_MODE
+#define OBJ_INFO_BUFFERS_NUM  10
+#define OBJ_INFO_BUFFERS_SIZE 0x100
+static int obj_info_buffers_index = 0;
+static char obj_info_buffers[OBJ_INFO_BUFFERS_NUM][OBJ_INFO_BUFFERS_SIZE];
+
+/* from array.c */
+# define ARY_SHARED_P(ary) \
+    (assert(!FL_TEST((ary), ELTS_SHARED) || !FL_TEST((ary), RARRAY_EMBED_FLAG)), \
+     FL_TEST((ary),ELTS_SHARED)!=0)
+# define ARY_EMBED_P(ary) \
+    (assert(!FL_TEST((ary), ELTS_SHARED) || !FL_TEST((ary), RARRAY_EMBED_FLAG)), \
+     FL_TEST((ary), RARRAY_EMBED_FLAG)!=0)
+
+static const char *
+obj_info(VALUE obj)
+{
+    int index = obj_info_buffers_index++;
+    char *buff = &obj_info_buffers[index][0];
+    int age = RVALUE_FLAGS_AGE(RBASIC(obj)->flags);
+
+    if (obj_info_buffers_index >= OBJ_INFO_BUFFERS_NUM) {
+	obj_info_buffers_index = 0;
+    }
+
+#define TF(c) ((c) != 0 ? "true" : "false")
+#define C(c, s) ((c) != 0 ? (s) : " ")
+    snprintf(buff, OBJ_INFO_BUFFERS_SIZE, "%p [%d%s%s%s%s] %s",
+	     (void *)obj, age,
+	     C(RVALUE_LONG_LIVED_BITMAP(obj),     "L"),
+	     C(RVALUE_MARK_BITMAP(obj),           "M"),
+	     C(RVALUE_MARKING_BITMAP(obj),        "R"),
+	     C(RVALUE_WB_UNPROTECTED_BITMAP(obj), "U"),
+	     obj_type_name(obj));
+
+#ifdef HAVE_VA_ARGS_MACRO
+    switch (BUILTIN_TYPE(obj)) {
+      case T_ARRAY:
+	snprintf(buff, OBJ_INFO_BUFFERS_SIZE, "%s [%s%s] len: %d", buff,
+		 C(ARY_EMBED_P(obj),  "E"),
+		 C(ARY_SHARED_P(obj), "S"),
+		 (int)RARRAY_LEN(obj));
+	break;
+      case T_STRING: {
+	  snprintf(buff, OBJ_INFO_BUFFERS_SIZE, "%s %s", buff, RSTRING_PTR(obj));
+	  break;
+      }
+      case T_CLASS: {
+	  VALUE class_path = rb_class_path_cached(obj);
+	  if (!NIL_P(class_path)) {
+	      snprintf(buff, OBJ_INFO_BUFFERS_SIZE, "%s %s", buff, RSTRING_PTR(class_path));
+	  }
+	  break;
+      }
+      case T_DATA: {
+	  const char *type_name = rb_objspace_data_type_name(obj);
+	  if (type_name && strcmp(type_name, "iseq") == 0) {
+	      rb_iseq_t *iseq;
+	      GetISeqPtr(obj, iseq);
+	      if (iseq->location.label) {
+		  snprintf(buff, OBJ_INFO_BUFFERS_SIZE, "%s %s@%s:%d", buff,
+			   RSTRING_PTR(iseq->location.label), RSTRING_PTR(iseq->location.path), (int)iseq->location.first_lineno);
+	      }
+	  }
+	  break;
+      }
+      default:
+	break;
+    }
+#endif
+#undef TF
+#undef C
+
+    return buff;
+}
+
+#else
+static const char *
+obj_info(VALUE obj)
+{
+    return obj_type_name(obj);
+}
+#endif
+
+#if GC_DEBUG
+
+void
+rb_gcdebug_print_obj_condition(VALUE obj)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+
+    fprintf(stderr, "created at: %s:%d\n", RANY(obj)->file, RANY(obj)->line);
+
+    if (is_pointer_to_heap(objspace, (void *)obj)) {
+        fprintf(stderr, "pointer to heap?: true\n");
+    }
+    else {
+        fprintf(stderr, "pointer to heap?: false\n");
+        return;
+    }
+
+    fprintf(stderr, "marked?      : %s\n", MARKED_IN_BITMAP(GET_HEAP_MARK_BITS(obj), obj) ? "true" : "false");
+#if USE_RGENGC
+    fprintf(stderr, "age?         : %d\n", RVALUE_AGE(obj));
+    fprintf(stderr, "old?         : %s\n", RVALUE_OLD_P(obj) ? "true" : "false");
+    fprintf(stderr, "WB-protected?: %s\n", RVALUE_WB_UNPROTECTED(obj) ? "false" : "true");
+    fprintf(stderr, "remembered?  : %s\n", RVALUE_REMEMBERED(obj) ? "true" : "false");
+#endif
+
+    if (is_lazy_sweeping(heap_eden)) {
+        fprintf(stderr, "lazy sweeping?: true\n");
+        fprintf(stderr, "swept?: %s\n", is_swept_object(objspace, obj) ? "done" : "not yet");
+    }
+    else {
+        fprintf(stderr, "lazy sweeping?: false\n");
+    }
+}
+
+static VALUE
+gcdebug_sentinel(VALUE obj, VALUE name)
+{
+    fprintf(stderr, "WARNING: object %s(%p) is inadvertently collected\n", (char *)name, (void *)obj);
+    return Qnil;
+}
+
+void
+rb_gcdebug_sentinel(VALUE obj, const char *name)
+{
+    rb_define_finalizer(obj, rb_proc_new(gcdebug_sentinel, (VALUE)name));
+}
+
+#endif /* GC_DEBUG */
+
+/*
+ * Document-module: ObjectSpace
+ *
+ *  The ObjectSpace module contains a number of routines
+ *  that interact with the garbage collection facility and allow you to
+ *  traverse all living objects with an iterator.
+ *
+ *  ObjectSpace also provides support for object finalizers, procs that will be
+ *  called when a specific object is about to be destroyed by garbage
+ *  collection.
+ *
+ *     a = "A"
+ *     b = "B"
+ *
+ *     ObjectSpace.define_finalizer(a, proc {|id| puts "Finalizer one on #{id}" })
+ *     ObjectSpace.define_finalizer(b, proc {|id| puts "Finalizer two on #{id}" })
+ *
+ *  _produces:_
+ *
+ *     Finalizer two on 537763470
+ *     Finalizer one on 537763480
+ */
+
+/*
+ *  Document-class: ObjectSpace::WeakMap
+ *
+ *  An ObjectSpace::WeakMap object holds references to
+ *  any objects, but those objects can get garbage collected.
+ *
+ *  This class is mostly used internally by WeakRef, please use
+ *  +lib/weakref.rb+ for the public interface.
+ */
+
+/*  Document-class: GC::Profiler
+ *
+ *  The GC profiler provides access to information on GC runs including time,
+ *  length and object space size.
+ *
+ *  Example:
+ *
+ *    GC::Profiler.enable
+ *
+ *    require 'rdoc/rdoc'
+ *
+ *    GC::Profiler.report
+ *
+ *    GC::Profiler.disable
+ *
+ *  See also GC.count, GC.malloc_allocated_size and GC.malloc_allocations
+ */
+
+/*
+ *  The GC module provides an interface to Ruby's mark and
+ *  sweep garbage collection mechanism.
+ *
+ *  Some of the underlying methods are also available via the ObjectSpace
+ *  module.
+ *
+ *  You may obtain information about the operation of the GC through
+ *  GC::Profiler.
+ */
+
+void
+Init_GC(void)
+{
+#undef rb_intern
+    VALUE rb_mObjSpace;
+    VALUE rb_mProfiler;
+    VALUE gc_constants;
+
+    rb_mGC = rb_define_module("GC");
+    rb_define_singleton_method(rb_mGC, "start", gc_start_internal, -1);
+    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_m, 1);
+    rb_define_singleton_method(rb_mGC, "count", gc_count, 0);
+    rb_define_singleton_method(rb_mGC, "stat", gc_stat, -1);
+    rb_define_singleton_method(rb_mGC, "latest_gc_info", gc_latest_gc_info, -1);
+    rb_define_method(rb_mGC, "garbage_collect", gc_start_internal, -1);
+
+    gc_constants = rb_hash_new();
+    rb_hash_aset(gc_constants, ID2SYM(rb_intern("RVALUE_SIZE")), SIZET2NUM(sizeof(RVALUE)));
+    rb_hash_aset(gc_constants, ID2SYM(rb_intern("HEAP_OBJ_LIMIT")), SIZET2NUM(HEAP_OBJ_LIMIT));
+    rb_hash_aset(gc_constants, ID2SYM(rb_intern("HEAP_BITMAP_SIZE")), SIZET2NUM(HEAP_BITMAP_SIZE));
+    rb_hash_aset(gc_constants, ID2SYM(rb_intern("HEAP_BITMAP_PLANES")), SIZET2NUM(HEAP_BITMAP_PLANES));
+    OBJ_FREEZE(gc_constants);
+    rb_define_const(rb_mGC, "INTERNAL_CONSTANTS", gc_constants);
+
+    rb_mProfiler = rb_define_module_under(rb_mGC, "Profiler");
+    rb_define_singleton_method(rb_mProfiler, "enabled?", gc_profile_enable_get, 0);
+    rb_define_singleton_method(rb_mProfiler, "enable", gc_profile_enable, 0);
+    rb_define_singleton_method(rb_mProfiler, "raw_data", gc_profile_record_get, 0);
+    rb_define_singleton_method(rb_mProfiler, "disable", gc_profile_disable, 0);
+    rb_define_singleton_method(rb_mProfiler, "clear", gc_profile_clear, 0);
+    rb_define_singleton_method(rb_mProfiler, "result", gc_profile_result, 0);
+    rb_define_singleton_method(rb_mProfiler, "report", gc_profile_report, -1);
+    rb_define_singleton_method(rb_mProfiler, "total_time", gc_profile_total_time, 0);
+
+    rb_mObjSpace = rb_define_module("ObjectSpace");
+    rb_define_module_function(rb_mObjSpace, "each_object", os_each_obj, -1);
+    rb_define_module_function(rb_mObjSpace, "garbage_collect", gc_start_internal, -1);
+
+    rb_define_module_function(rb_mObjSpace, "define_finalizer", define_final, -1);
+    rb_define_module_function(rb_mObjSpace, "undefine_finalizer", undefine_final, 1);
+
+    rb_define_module_function(rb_mObjSpace, "_id2ref", id2ref, 1);
+
+    rb_vm_register_special_exception(ruby_error_nomemory, rb_eNoMemError, "failed to allocate memory");
+
+    rb_define_method(rb_cBasicObject, "__id__", rb_obj_id, 0);
+    rb_define_method(rb_mKernel, "object_id", rb_obj_id, 0);
+
+    rb_define_module_function(rb_mObjSpace, "count_objects", count_objects, -1);
+
+    {
+	VALUE rb_cWeakMap = rb_define_class_under(rb_mObjSpace, "WeakMap", rb_cObject);
+	rb_define_alloc_func(rb_cWeakMap, wmap_allocate);
+	rb_define_method(rb_cWeakMap, "[]=", wmap_aset, 2);
+	rb_define_method(rb_cWeakMap, "[]", wmap_aref, 1);
+	rb_define_method(rb_cWeakMap, "include?", wmap_has_key, 1);
+	rb_define_method(rb_cWeakMap, "member?", wmap_has_key, 1);
+	rb_define_method(rb_cWeakMap, "key?", wmap_has_key, 1);
+	rb_define_method(rb_cWeakMap, "inspect", wmap_inspect, 0);
+	rb_define_method(rb_cWeakMap, "each", wmap_each, 0);
+	rb_define_method(rb_cWeakMap, "each_pair", wmap_each, 0);
+	rb_define_method(rb_cWeakMap, "each_key", wmap_each_key, 0);
+	rb_define_method(rb_cWeakMap, "each_value", wmap_each_value, 0);
+	rb_define_method(rb_cWeakMap, "keys", wmap_keys, 0);
+	rb_define_method(rb_cWeakMap, "values", wmap_values, 0);
+	rb_define_method(rb_cWeakMap, "size", wmap_size, 0);
+	rb_define_method(rb_cWeakMap, "length", wmap_size, 0);
+	rb_define_private_method(rb_cWeakMap, "finalize", wmap_finalize, 1);
+	rb_include_module(rb_cWeakMap, rb_mEnumerable);
+    }
+
+    /* internal methods */
+    rb_define_singleton_method(rb_mGC, "verify_internal_consistency", gc_verify_internal_consistency, 0);
+#if MALLOC_ALLOCATED_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
+
+    /* ::GC::OPTS, which shows GC build options */
+    {
+	VALUE opts;
+	rb_define_const(rb_mGC, "OPTS", opts = rb_ary_new());
+#define OPT(o) if (o) rb_ary_push(opts, rb_fstring_new(#o, strlen(#o)))
+	OPT(GC_DEBUG);
+	OPT(USE_RGENGC);
+	OPT(RGENGC_DEBUG);
+	OPT(RGENGC_CHECK_MODE);
+	OPT(RGENGC_PROFILE);
+	OPT(RGENGC_ESTIMATE_OLDMALLOC);
+	OPT(GC_PROFILE_MORE_DETAIL);
+	OPT(GC_ENABLE_LAZY_SWEEP);
+	OPT(CALC_EXACT_MALLOC_SIZE);
+	OPT(MALLOC_ALLOCATED_SIZE);
+	OPT(MALLOC_ALLOCATED_SIZE_CHECK);
+	OPT(GC_PROFILE_DETAIL_MEMORY);
+#undef OPT
+	OBJ_FREEZE(opts);
+    }
+}