Fresh start

1 files changed, 2659 insertions, 0 deletions

diff --git a/jni/ruby/variable.c b/jni/ruby/variable.c
new file mode 100644
index 0000000..19ebd03
--- /dev/null
+++ b/jni/ruby/variable.c
@@ -0,0 +1,2659 @@
+/**********************************************************************
+
+  variable.c -
+
+  $Author: nobu $
+  created at: Tue Apr 19 23:55:15 JST 1994
+
+  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/util.h"
+#include "node.h"
+#include "constant.h"
+#include "id.h"
+
+st_table *rb_global_tbl;
+static ID autoload, classpath, tmp_classpath, classid;
+
+void
+Init_var_tables(void)
+{
+    rb_global_tbl = st_init_numtable();
+    autoload = rb_intern_const("__autoload__");
+    /* __classpath__: fully qualified class path */
+    classpath = rb_intern_const("__classpath__");
+    /* __tmp_classpath__: temporary class path which contains anonymous names */
+    tmp_classpath = rb_intern_const("__tmp_classpath__");
+    /* __classid__: name given to class/module under an anonymous namespace */
+    classid = rb_intern_const("__classid__");
+}
+
+struct fc_result {
+    ID name, preferred;
+    VALUE klass;
+    VALUE path;
+    VALUE track;
+    struct fc_result *prev;
+};
+
+static VALUE
+fc_path(struct fc_result *fc, ID name)
+{
+    VALUE path, tmp;
+
+    path = rb_id2str(name);
+    while (fc) {
+	st_data_t n;
+	if (fc->track == rb_cObject) break;
+	if (RCLASS_IV_TBL(fc->track) &&
+	    st_lookup(RCLASS_IV_TBL(fc->track), (st_data_t)classpath, &n)) {
+	    tmp = rb_str_dup((VALUE)n);
+	    rb_str_cat2(tmp, "::");
+	    rb_str_append(tmp, path);
+	    path = tmp;
+	    break;
+	}
+	tmp = rb_str_dup(rb_id2str(fc->name));
+	rb_str_cat2(tmp, "::");
+	rb_str_append(tmp, path);
+	path = tmp;
+	fc = fc->prev;
+    }
+    OBJ_FREEZE(path);
+    return path;
+}
+
+static int
+fc_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    ID key = (ID)k;
+    rb_const_entry_t *ce = (rb_const_entry_t *)v;
+    struct fc_result *res = (struct fc_result *)a;
+    VALUE value = ce->value;
+    if (!rb_is_const_id(key)) return ST_CONTINUE;
+
+    if (value == res->klass && (!res->preferred || key == res->preferred)) {
+	res->path = fc_path(res, key);
+	return ST_STOP;
+    }
+    if (RB_TYPE_P(value, T_MODULE) || RB_TYPE_P(value, T_CLASS)) {
+	if (!RCLASS_CONST_TBL(value)) return ST_CONTINUE;
+	else {
+	    struct fc_result arg;
+	    struct fc_result *list;
+
+	    list = res;
+	    while (list) {
+		if (list->track == value) return ST_CONTINUE;
+		list = list->prev;
+	    }
+
+	    arg.name = key;
+	    arg.preferred = res->preferred;
+	    arg.path = 0;
+	    arg.klass = res->klass;
+	    arg.track = value;
+	    arg.prev = res;
+	    st_foreach(RCLASS_CONST_TBL(value), fc_i, (st_data_t)&arg);
+	    if (arg.path) {
+		res->path = arg.path;
+		return ST_STOP;
+	    }
+	}
+    }
+    return ST_CONTINUE;
+}
+
+/**
+ * Traverse constant namespace and find +classpath+ for _klass_.  If
+ * _preferred_ is not 0, choice the path whose base name is set to it.
+ * If +classpath+ is found, the hidden instance variable __classpath__
+ * is set to the found path, and __tmp_classpath__ is removed.
+ * The path is frozen.
+ */
+static VALUE
+find_class_path(VALUE klass, ID preferred)
+{
+    struct fc_result arg;
+
+    arg.preferred = preferred;
+    arg.name = 0;
+    arg.path = 0;
+    arg.klass = klass;
+    arg.track = rb_cObject;
+    arg.prev = 0;
+    if (RCLASS_CONST_TBL(rb_cObject)) {
+	st_foreach_safe(RCLASS_CONST_TBL(rb_cObject), fc_i, (st_data_t)&arg);
+    }
+    if (arg.path) {
+	st_data_t tmp = tmp_classpath;
+	if (!RCLASS_IV_TBL(klass)) {
+	    RCLASS_IV_TBL(klass) = st_init_numtable();
+	}
+	rb_st_insert_id_and_value(klass, RCLASS_IV_TBL(klass), (st_data_t)classpath, arg.path);
+
+	st_delete(RCLASS_IV_TBL(klass), &tmp, 0);
+	return arg.path;
+    }
+    return Qnil;
+}
+
+/**
+ * Returns +classpath+ of _klass_, if it is named, or +nil+ for
+ * anonymous +class+/+module+.  The last part of named +classpath+ is
+ * never anonymous, but anonymous +class+/+module+ names may be
+ * contained.  If the path is "permanent", that means it has no
+ * anonymous names, <code>*permanent</code> is set to 1.
+ */
+static VALUE
+classname(VALUE klass, int *permanent)
+{
+    VALUE path = Qnil;
+    st_data_t n;
+
+    if (!klass) klass = rb_cObject;
+    *permanent = 1;
+    if (RCLASS_IV_TBL(klass)) {
+	if (!st_lookup(RCLASS_IV_TBL(klass), (st_data_t)classpath, &n)) {
+	    ID cid = 0;
+	    if (st_lookup(RCLASS_IV_TBL(klass), (st_data_t)classid, &n)) {
+		cid = SYM2ID(n);
+		path = find_class_path(klass, cid);
+	    }
+	    if (NIL_P(path)) {
+		path = find_class_path(klass, (ID)0);
+	    }
+	    if (NIL_P(path)) {
+		if (!cid) {
+		    return Qnil;
+		}
+		if (!st_lookup(RCLASS_IV_TBL(klass), (st_data_t)tmp_classpath, &n)) {
+		    path = rb_id2str(cid);
+		    return path;
+		}
+		*permanent = 0;
+		path = (VALUE)n;
+		return path;
+	    }
+	}
+	else {
+	    path = (VALUE)n;
+	}
+	if (!RB_TYPE_P(path, T_STRING)) {
+	    rb_bug("class path is not set properly");
+	}
+	return path;
+    }
+    return find_class_path(klass, (ID)0);
+}
+
+/*
+ *  call-seq:
+ *     mod.name    -> string
+ *
+ *  Returns the name of the module <i>mod</i>.  Returns nil for anonymous modules.
+ */
+
+VALUE
+rb_mod_name(VALUE mod)
+{
+    int permanent;
+    VALUE path = classname(mod, &permanent);
+
+    if (!NIL_P(path)) return rb_str_dup(path);
+    return path;
+}
+
+typedef VALUE (*path_cache_func)(VALUE obj, ID id, VALUE val);
+
+static VALUE
+rb_tmp_class_path(VALUE klass, int *permanent, path_cache_func cache_path)
+{
+    VALUE path = classname(klass, permanent);
+    st_data_t n = (st_data_t)path;
+
+    if (!NIL_P(path)) {
+	return path;
+    }
+    if (RCLASS_IV_TBL(klass) && st_lookup(RCLASS_IV_TBL(klass),
+					  (st_data_t)tmp_classpath, &n)) {
+	*permanent = 0;
+	return (VALUE)n;
+    }
+    else {
+	const char *s = "Class";
+
+	if (RB_TYPE_P(klass, T_MODULE)) {
+	    if (rb_obj_class(klass) == rb_cModule) {
+		s = "Module";
+	    }
+	    else {
+		int perm;
+		VALUE path;
+
+		path = rb_tmp_class_path(RBASIC(klass)->klass, &perm, cache_path);
+		s = RSTRING_PTR(path);
+	    }
+	}
+	path = rb_sprintf("#<%s:%p>", s, (void*)klass);
+	OBJ_FREEZE(path);
+
+	cache_path(klass, tmp_classpath, path);
+	*permanent = 0;
+
+	return path;
+    }
+}
+
+VALUE
+rb_class_path(VALUE klass)
+{
+    int permanent;
+    VALUE path = rb_tmp_class_path(klass, &permanent, rb_ivar_set);
+    if (!NIL_P(path)) path = rb_str_dup(path);
+    return path;
+}
+
+static VALUE
+null_cache(VALUE obj, ID id, VALUE val)
+{
+    return Qnil;
+}
+
+VALUE
+rb_class_path_no_cache(VALUE klass)
+{
+    int permanent;
+    VALUE path = rb_tmp_class_path(klass, &permanent, null_cache);
+    if (!NIL_P(path)) path = rb_str_dup(path);
+    return path;
+}
+
+VALUE
+rb_class_path_cached(VALUE klass)
+{
+    st_table *ivtbl = RCLASS_IV_TBL(klass);
+    st_data_t n;
+
+    if (!ivtbl) return Qnil;
+    if (st_lookup(ivtbl, (st_data_t)classpath, &n)) return (VALUE)n;
+    if (st_lookup(ivtbl, (st_data_t)tmp_classpath, &n)) return (VALUE)n;
+    return Qnil;
+}
+
+void
+rb_set_class_path_string(VALUE klass, VALUE under, VALUE name)
+{
+    VALUE str;
+    ID pathid = classpath;
+
+    if (under == rb_cObject) {
+	str = rb_str_new_frozen(name);
+    }
+    else {
+	int permanent;
+	str = rb_str_dup(rb_tmp_class_path(under, &permanent, rb_ivar_set));
+	rb_str_cat2(str, "::");
+	rb_str_append(str, name);
+	OBJ_FREEZE(str);
+	if (!permanent) {
+	    pathid = tmp_classpath;
+	    rb_ivar_set(klass, classid, ID2SYM(rb_intern_str(name)));
+	}
+    }
+    rb_ivar_set(klass, pathid, str);
+}
+
+void
+rb_set_class_path(VALUE klass, VALUE under, const char *name)
+{
+    VALUE str;
+    ID pathid = classpath;
+
+    if (under == rb_cObject) {
+	str = rb_str_new2(name);
+    }
+    else {
+	int permanent;
+	str = rb_str_dup(rb_tmp_class_path(under, &permanent, rb_ivar_set));
+	rb_str_cat2(str, "::");
+	rb_str_cat2(str, name);
+	if (!permanent) {
+	    pathid = tmp_classpath;
+	    rb_ivar_set(klass, classid, ID2SYM(rb_intern(name)));
+	}
+    }
+    OBJ_FREEZE(str);
+    rb_ivar_set(klass, pathid, str);
+}
+
+VALUE
+rb_path_to_class(VALUE pathname)
+{
+    rb_encoding *enc = rb_enc_get(pathname);
+    const char *pbeg, *p, *path = RSTRING_PTR(pathname);
+    ID id;
+    VALUE c = rb_cObject;
+
+    if (!rb_enc_asciicompat(enc)) {
+	rb_raise(rb_eArgError, "invalid class path encoding (non ASCII)");
+    }
+    pbeg = p = path;
+    if (path[0] == '#') {
+	rb_raise(rb_eArgError, "can't retrieve anonymous class %"PRIsVALUE,
+		 QUOTE(pathname));
+    }
+    while (*p) {
+	while (*p && *p != ':') p++;
+	id = rb_check_id_cstr(pbeg, p-pbeg, enc);
+	if (p[0] == ':') {
+	    if (p[1] != ':') goto undefined_class;
+	    p += 2;
+	    pbeg = p;
+	}
+	if (!id || !rb_const_defined_at(c, id)) {
+	  undefined_class:
+	    rb_raise(rb_eArgError, "undefined class/module %.*"PRIsVALUE,
+		     (int)(p-path), pathname);
+	}
+	c = rb_const_get_at(c, id);
+	if (!RB_TYPE_P(c, T_MODULE) && !RB_TYPE_P(c, T_CLASS)) {
+	    rb_raise(rb_eTypeError, "%"PRIsVALUE" does not refer to class/module",
+		     pathname);
+	}
+    }
+    RB_GC_GUARD(pathname);
+
+    return c;
+}
+
+VALUE
+rb_path2class(const char *path)
+{
+    return rb_path_to_class(rb_str_new_cstr(path));
+}
+
+void
+rb_name_class(VALUE klass, ID id)
+{
+    rb_ivar_set(klass, classid, ID2SYM(id));
+}
+
+VALUE
+rb_class_name(VALUE klass)
+{
+    return rb_class_path(rb_class_real(klass));
+}
+
+const char *
+rb_class2name(VALUE klass)
+{
+    int permanent;
+    VALUE path = rb_tmp_class_path(rb_class_real(klass), &permanent, rb_ivar_set);
+    if (NIL_P(path)) return NULL;
+    return RSTRING_PTR(path);
+}
+
+const char *
+rb_obj_classname(VALUE obj)
+{
+    return rb_class2name(CLASS_OF(obj));
+}
+
+#define global_variable rb_global_variable
+#define global_entry rb_global_entry
+
+#define gvar_getter_t rb_gvar_getter_t
+#define gvar_setter_t rb_gvar_setter_t
+#define gvar_marker_t rb_gvar_marker_t
+
+struct trace_var {
+    int removed;
+    void (*func)(VALUE arg, VALUE val);
+    VALUE data;
+    struct trace_var *next;
+};
+
+struct global_variable {
+    int   counter;
+    int block_trace;
+    void *data;
+    gvar_getter_t *getter;
+    gvar_setter_t *setter;
+    gvar_marker_t *marker;
+    struct trace_var *trace;
+};
+
+#define undef_getter	rb_gvar_undef_getter
+#define undef_setter	rb_gvar_undef_setter
+#define undef_marker	rb_gvar_undef_marker
+
+#define val_getter	rb_gvar_val_getter
+#define val_setter	rb_gvar_val_setter
+#define val_marker	rb_gvar_val_marker
+
+#define var_getter	rb_gvar_var_getter
+#define var_setter	rb_gvar_var_setter
+#define var_marker	rb_gvar_var_marker
+
+#define readonly_setter rb_gvar_readonly_setter
+
+struct global_entry*
+rb_global_entry(ID id)
+{
+    struct global_entry *entry;
+    st_data_t data;
+
+    if (!st_lookup(rb_global_tbl, (st_data_t)id, &data)) {
+	struct global_variable *var;
+	entry = ALLOC(struct global_entry);
+	var = ALLOC(struct global_variable);
+	entry->id = id;
+	entry->var = var;
+	var->counter = 1;
+	var->data = 0;
+	var->getter = undef_getter;
+	var->setter = undef_setter;
+	var->marker = undef_marker;
+
+	var->block_trace = 0;
+	var->trace = 0;
+	st_add_direct(rb_global_tbl, id, (st_data_t)entry);
+    }
+    else {
+	entry = (struct global_entry *)data;
+    }
+    return entry;
+}
+
+VALUE
+undef_getter(ID id, void *data, struct global_variable *var)
+{
+    rb_warning("global variable `%"PRIsVALUE"' not initialized", QUOTE_ID(id));
+
+    return Qnil;
+}
+
+void
+undef_setter(VALUE val, ID id, void *data, struct global_variable *var)
+{
+    var->getter = val_getter;
+    var->setter = val_setter;
+    var->marker = val_marker;
+
+    var->data = (void*)val;
+}
+
+void
+undef_marker(VALUE *var)
+{
+}
+
+VALUE
+val_getter(ID id, void *data, struct global_variable *var)
+{
+    return (VALUE)data;
+}
+
+void
+val_setter(VALUE val, ID id, void *data, struct global_variable *var)
+{
+    var->data = (void*)val;
+}
+
+void
+val_marker(VALUE *var)
+{
+    VALUE data = (VALUE)var;
+    if (data) rb_gc_mark_maybe(data);
+}
+
+VALUE
+var_getter(ID id, void *data, struct global_variable *gvar)
+{
+    VALUE *var = data;
+    if (!var) return Qnil;
+    return *var;
+}
+
+void
+var_setter(VALUE val, ID id, void *data, struct global_variable *gvar)
+{
+    *(VALUE *)data = val;
+}
+
+void
+var_marker(VALUE *var)
+{
+    if (var) rb_gc_mark_maybe(*var);
+}
+
+void
+readonly_setter(VALUE val, ID id, void *data, struct global_variable *gvar)
+{
+    rb_name_error(id, "%"PRIsVALUE" is a read-only variable", QUOTE_ID(id));
+}
+
+static int
+mark_global_entry(st_data_t k, st_data_t v, st_data_t a)
+{
+    struct global_entry *entry = (struct global_entry *)v;
+    struct trace_var *trace;
+    struct global_variable *var = entry->var;
+
+    (*var->marker)(var->data);
+    trace = var->trace;
+    while (trace) {
+	if (trace->data) rb_gc_mark_maybe(trace->data);
+	trace = trace->next;
+    }
+    return ST_CONTINUE;
+}
+
+void
+rb_gc_mark_global_tbl(void)
+{
+    if (rb_global_tbl)
+        st_foreach_safe(rb_global_tbl, mark_global_entry, 0);
+}
+
+static ID
+global_id(const char *name)
+{
+    ID id;
+
+    if (name[0] == '$') id = rb_intern(name);
+    else {
+	size_t len = strlen(name);
+	char *buf = ALLOCA_N(char, len+1);
+	buf[0] = '$';
+	memcpy(buf+1, name, len);
+	id = rb_intern2(buf, len+1);
+    }
+    return id;
+}
+
+void
+rb_define_hooked_variable(
+    const char *name,
+    VALUE *var,
+    VALUE (*getter)(ANYARGS),
+    void  (*setter)(ANYARGS))
+{
+    volatile VALUE tmp = var ? *var : Qnil;
+    ID id = global_id(name);
+    struct global_variable *gvar = rb_global_entry(id)->var;
+
+    gvar->data = (void*)var;
+    gvar->getter = getter?(gvar_getter_t *)getter:var_getter;
+    gvar->setter = setter?(gvar_setter_t *)setter:var_setter;
+    gvar->marker = var_marker;
+
+    RB_GC_GUARD(tmp);
+}
+
+void
+rb_define_variable(const char *name, VALUE *var)
+{
+    rb_define_hooked_variable(name, var, 0, 0);
+}
+
+void
+rb_define_readonly_variable(const char *name, const VALUE *var)
+{
+    rb_define_hooked_variable(name, (VALUE *)var, 0, readonly_setter);
+}
+
+void
+rb_define_virtual_variable(
+    const char *name,
+    VALUE (*getter)(ANYARGS),
+    void  (*setter)(ANYARGS))
+{
+    if (!getter) getter = val_getter;
+    if (!setter) setter = readonly_setter;
+    rb_define_hooked_variable(name, 0, getter, setter);
+}
+
+static void
+rb_trace_eval(VALUE cmd, VALUE val)
+{
+    rb_eval_cmd(cmd, rb_ary_new3(1, val), 0);
+}
+
+/*
+ *  call-seq:
+ *     trace_var(symbol, cmd )             -> nil
+ *     trace_var(symbol) {|val| block }    -> nil
+ *
+ *  Controls tracing of assignments to global variables. The parameter
+ *  +symbol+ identifies the variable (as either a string name or a
+ *  symbol identifier). _cmd_ (which may be a string or a
+ *  +Proc+ object) or block is executed whenever the variable
+ *  is assigned. The block or +Proc+ object receives the
+ *  variable's new value as a parameter. Also see
+ *  <code>Kernel::untrace_var</code>.
+ *
+ *     trace_var :$_, proc {|v| puts "$_ is now '#{v}'" }
+ *     $_ = "hello"
+ *     $_ = ' there'
+ *
+ *  <em>produces:</em>
+ *
+ *     $_ is now 'hello'
+ *     $_ is now ' there'
+ */
+
+VALUE
+rb_f_trace_var(int argc, const VALUE *argv)
+{
+    VALUE var, cmd;
+    struct global_entry *entry;
+    struct trace_var *trace;
+
+    if (rb_scan_args(argc, argv, "11", &var, &cmd) == 1) {
+	cmd = rb_block_proc();
+    }
+    if (NIL_P(cmd)) {
+	return rb_f_untrace_var(argc, argv);
+    }
+    entry = rb_global_entry(rb_to_id(var));
+    if (OBJ_TAINTED(cmd)) {
+	rb_raise(rb_eSecurityError, "Insecure: tainted variable trace");
+    }
+    trace = ALLOC(struct trace_var);
+    trace->next = entry->var->trace;
+    trace->func = rb_trace_eval;
+    trace->data = cmd;
+    trace->removed = 0;
+    entry->var->trace = trace;
+
+    return Qnil;
+}
+
+static void
+remove_trace(struct global_variable *var)
+{
+    struct trace_var *trace = var->trace;
+    struct trace_var t;
+    struct trace_var *next;
+
+    t.next = trace;
+    trace = &t;
+    while (trace->next) {
+	next = trace->next;
+	if (next->removed) {
+	    trace->next = next->next;
+	    xfree(next);
+	}
+	else {
+	    trace = next;
+	}
+    }
+    var->trace = t.next;
+}
+
+/*
+ *  call-seq:
+ *     untrace_var(symbol [, cmd] )   -> array or nil
+ *
+ *  Removes tracing for the specified command on the given global
+ *  variable and returns +nil+. If no command is specified,
+ *  removes all tracing for that variable and returns an array
+ *  containing the commands actually removed.
+ */
+
+VALUE
+rb_f_untrace_var(int argc, const VALUE *argv)
+{
+    VALUE var, cmd;
+    ID id;
+    struct global_entry *entry;
+    struct trace_var *trace;
+    st_data_t data;
+
+    rb_scan_args(argc, argv, "11", &var, &cmd);
+    id = rb_check_id(&var);
+    if (!id) {
+	rb_name_error_str(var, "undefined global variable %"PRIsVALUE"", QUOTE(var));
+    }
+    if (!st_lookup(rb_global_tbl, (st_data_t)id, &data)) {
+	rb_name_error(id, "undefined global variable %"PRIsVALUE"", QUOTE_ID(id));
+    }
+
+    trace = (entry = (struct global_entry *)data)->var->trace;
+    if (NIL_P(cmd)) {
+	VALUE ary = rb_ary_new();
+
+	while (trace) {
+	    struct trace_var *next = trace->next;
+	    rb_ary_push(ary, (VALUE)trace->data);
+	    trace->removed = 1;
+	    trace = next;
+	}
+
+	if (!entry->var->block_trace) remove_trace(entry->var);
+	return ary;
+    }
+    else {
+	while (trace) {
+	    if (trace->data == cmd) {
+		trace->removed = 1;
+		if (!entry->var->block_trace) remove_trace(entry->var);
+		return rb_ary_new3(1, cmd);
+	    }
+	    trace = trace->next;
+	}
+    }
+    return Qnil;
+}
+
+VALUE
+rb_gvar_get(struct global_entry *entry)
+{
+    struct global_variable *var = entry->var;
+    return (*var->getter)(entry->id, var->data, var);
+}
+
+struct trace_data {
+    struct trace_var *trace;
+    VALUE val;
+};
+
+static VALUE
+trace_ev(struct trace_data *data)
+{
+    struct trace_var *trace = data->trace;
+
+    while (trace) {
+	(*trace->func)(trace->data, data->val);
+	trace = trace->next;
+    }
+
+    return Qnil;
+}
+
+static VALUE
+trace_en(struct global_variable *var)
+{
+    var->block_trace = 0;
+    remove_trace(var);
+    return Qnil;		/* not reached */
+}
+
+VALUE
+rb_gvar_set(struct global_entry *entry, VALUE val)
+{
+    struct trace_data trace;
+    struct global_variable *var = entry->var;
+
+    (*var->setter)(val, entry->id, var->data, var);
+
+    if (var->trace && !var->block_trace) {
+	var->block_trace = 1;
+	trace.trace = var->trace;
+	trace.val = val;
+	rb_ensure(trace_ev, (VALUE)&trace, trace_en, (VALUE)var);
+    }
+    return val;
+}
+
+VALUE
+rb_gv_set(const char *name, VALUE val)
+{
+    struct global_entry *entry;
+
+    entry = rb_global_entry(global_id(name));
+    return rb_gvar_set(entry, val);
+}
+
+VALUE
+rb_gv_get(const char *name)
+{
+    struct global_entry *entry;
+
+    entry = rb_global_entry(global_id(name));
+    return rb_gvar_get(entry);
+}
+
+VALUE
+rb_gvar_defined(struct global_entry *entry)
+{
+    if (entry->var->getter == undef_getter) return Qfalse;
+    return Qtrue;
+}
+
+static int
+gvar_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    ID key = (ID)k;
+    VALUE ary = (VALUE)a;
+    rb_ary_push(ary, ID2SYM(key));
+    return ST_CONTINUE;
+}
+
+/*
+ *  call-seq:
+ *     global_variables    -> array
+ *
+ *  Returns an array of the names of global variables.
+ *
+ *     global_variables.grep /std/   #=> [:$stdin, :$stdout, :$stderr]
+ */
+
+VALUE
+rb_f_global_variables(void)
+{
+    VALUE ary = rb_ary_new();
+    char buf[2];
+    int i;
+
+    st_foreach_safe(rb_global_tbl, gvar_i, ary);
+    buf[0] = '$';
+    for (i = 1; i <= 9; ++i) {
+	buf[1] = (char)(i + '0');
+	rb_ary_push(ary, ID2SYM(rb_intern2(buf, 2)));
+    }
+    return ary;
+}
+
+void
+rb_alias_variable(ID name1, ID name2)
+{
+    struct global_entry *entry1, *entry2;
+    st_data_t data1;
+
+    entry2 = rb_global_entry(name2);
+    if (!st_lookup(rb_global_tbl, (st_data_t)name1, &data1)) {
+	name1 = SYM2ID(ID2SYM(name1));
+	entry1 = ALLOC(struct global_entry);
+	entry1->id = name1;
+	st_add_direct(rb_global_tbl, name1, (st_data_t)entry1);
+    }
+    else if ((entry1 = (struct global_entry *)data1)->var != entry2->var) {
+	struct global_variable *var = entry1->var;
+	if (var->block_trace) {
+	    rb_raise(rb_eRuntimeError, "can't alias in tracer");
+	}
+	var->counter--;
+	if (var->counter == 0) {
+	    struct trace_var *trace = var->trace;
+	    while (trace) {
+		struct trace_var *next = trace->next;
+		xfree(trace);
+		trace = next;
+	    }
+	    xfree(var);
+	}
+    }
+    else {
+	return;
+    }
+    entry2->var->counter++;
+    entry1->var = entry2->var;
+}
+
+static int special_generic_ivar = 0;
+static st_table *generic_iv_tbl;
+
+st_table*
+rb_generic_ivar_table(VALUE obj)
+{
+    st_data_t tbl;
+
+    if (!FL_TEST(obj, FL_EXIVAR)) return 0;
+    if (!generic_iv_tbl) return 0;
+    if (!st_lookup(generic_iv_tbl, (st_data_t)obj, &tbl)) return 0;
+    return (st_table *)tbl;
+}
+
+static VALUE
+generic_ivar_get(VALUE obj, ID id, VALUE undef)
+{
+    st_data_t tbl, val;
+
+    if (generic_iv_tbl) {
+	if (st_lookup(generic_iv_tbl, (st_data_t)obj, &tbl)) {
+	    if (st_lookup((st_table *)tbl, (st_data_t)id, &val)) {
+		return (VALUE)val;
+	    }
+	}
+    }
+    return undef;
+}
+
+static int
+generic_ivar_update(st_data_t *k, st_data_t *v, st_data_t a, int existing)
+{
+    VALUE obj = (VALUE)*k;
+    st_table **tbl = (st_table **)a;
+
+    if (!existing) {
+	FL_SET(obj, FL_EXIVAR);
+	*v = (st_data_t)(*tbl = st_init_numtable());
+	return ST_CONTINUE;
+    }
+    else {
+	*tbl = (st_table *)*v;
+	return ST_STOP;
+    }
+}
+
+static void
+generic_ivar_set(VALUE obj, ID id, VALUE val)
+{
+    st_table *tbl;
+
+    if (rb_special_const_p(obj)) {
+	if (rb_obj_frozen_p(obj)) rb_error_frozen("object");
+	special_generic_ivar = 1;
+    }
+    if (!generic_iv_tbl) {
+	generic_iv_tbl = st_init_numtable();
+    }
+    if (!st_update(generic_iv_tbl, (st_data_t)obj,
+		   generic_ivar_update, (st_data_t)&tbl)) {
+	st_add_direct(tbl, (st_data_t)id, (st_data_t)val);
+    }
+    else {
+	st_insert(tbl, (st_data_t)id, (st_data_t)val);
+    }
+    if (FL_ABLE(obj)) RB_OBJ_WRITTEN(obj, Qundef, val);
+}
+
+static VALUE
+generic_ivar_defined(VALUE obj, ID id)
+{
+    st_table *tbl;
+    st_data_t data;
+
+    if (!generic_iv_tbl) return Qfalse;
+    if (!st_lookup(generic_iv_tbl, (st_data_t)obj, &data)) return Qfalse;
+    tbl = (st_table *)data;
+    if (st_lookup(tbl, (st_data_t)id, &data)) {
+	return Qtrue;
+    }
+    return Qfalse;
+}
+
+static int
+generic_ivar_remove(VALUE obj, ID id, st_data_t *valp)
+{
+    st_table *tbl;
+    st_data_t data, key = (st_data_t)id;
+    int status;
+
+    if (!generic_iv_tbl) return 0;
+    if (!st_lookup(generic_iv_tbl, (st_data_t)obj, &data)) return 0;
+    tbl = (st_table *)data;
+    status = st_delete(tbl, &key, valp);
+    if (tbl->num_entries == 0) {
+	key = (st_data_t)obj;
+	st_delete(generic_iv_tbl, &key, &data);
+	st_free_table((st_table *)data);
+    }
+    return status;
+}
+
+void
+rb_mark_generic_ivar(VALUE obj)
+{
+    st_data_t tbl;
+
+    if (!generic_iv_tbl) return;
+    if (st_lookup(generic_iv_tbl, (st_data_t)obj, &tbl)) {
+	rb_mark_tbl((st_table *)tbl);
+    }
+}
+
+static int
+givar_mark_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    VALUE value = (VALUE)v;
+    rb_gc_mark(value);
+    return ST_CONTINUE;
+}
+
+static int
+givar_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    VALUE obj = (VALUE)k;
+    st_table *tbl = (st_table *)v;
+    if (rb_special_const_p(obj)) {
+	st_foreach_safe(tbl, givar_mark_i, 0);
+    }
+    return ST_CONTINUE;
+}
+
+void
+rb_mark_generic_ivar_tbl(void)
+{
+    if (!generic_iv_tbl) return;
+    if (special_generic_ivar == 0) return;
+    st_foreach_safe(generic_iv_tbl, givar_i, 0);
+}
+
+void
+rb_free_generic_ivar(VALUE obj)
+{
+    st_data_t key = (st_data_t)obj, tbl;
+
+    if (!generic_iv_tbl) return;
+    if (st_delete(generic_iv_tbl, &key, &tbl))
+	st_free_table((st_table *)tbl);
+}
+
+RUBY_FUNC_EXPORTED size_t
+rb_generic_ivar_memsize(VALUE obj)
+{
+    st_data_t tbl;
+    if (st_lookup(generic_iv_tbl, (st_data_t)obj, &tbl))
+	return st_memsize((st_table *)tbl);
+    return 0;
+}
+
+void
+rb_copy_generic_ivar(VALUE clone, VALUE obj)
+{
+    st_data_t data;
+
+    if (!generic_iv_tbl) return;
+    if (!FL_TEST(obj, FL_EXIVAR)) {
+      clear:
+        if (FL_TEST(clone, FL_EXIVAR)) {
+            rb_free_generic_ivar(clone);
+            FL_UNSET(clone, FL_EXIVAR);
+        }
+        return;
+    }
+    if (st_lookup(generic_iv_tbl, (st_data_t)obj, &data)) {
+	st_table *tbl = (st_table *)data;
+
+        if (tbl->num_entries == 0)
+            goto clear;
+
+	if (st_lookup(generic_iv_tbl, (st_data_t)clone, &data)) {
+	    st_free_table((st_table *)data);
+	    st_insert(generic_iv_tbl, (st_data_t)clone, (st_data_t)st_copy(tbl));
+	}
+	else {
+	    st_add_direct(generic_iv_tbl, (st_data_t)clone, (st_data_t)st_copy(tbl));
+	    FL_SET(clone, FL_EXIVAR);
+	}
+    }
+}
+
+static VALUE
+rb_ivar_lookup(VALUE obj, ID id, VALUE undef)
+{
+    VALUE val, *ptr;
+    struct st_table *iv_index_tbl;
+    long len;
+    st_data_t index;
+
+    if (SPECIAL_CONST_P(obj)) goto generic;
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+        len = ROBJECT_NUMIV(obj);
+        ptr = ROBJECT_IVPTR(obj);
+        iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
+        if (!iv_index_tbl) break;
+        if (!st_lookup(iv_index_tbl, (st_data_t)id, &index)) break;
+        if (len <= (long)index) break;
+        val = ptr[index];
+        if (val != Qundef)
+            return val;
+	break;
+      case T_CLASS:
+      case T_MODULE:
+	if (RCLASS_IV_TBL(obj) && st_lookup(RCLASS_IV_TBL(obj), (st_data_t)id, &index))
+	    return (VALUE)index;
+	break;
+      default:
+      generic:
+	if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj))
+	    return generic_ivar_get(obj, id, undef);
+	break;
+    }
+    return undef;
+}
+
+VALUE
+rb_ivar_get(VALUE obj, ID id)
+{
+    VALUE iv = rb_ivar_lookup(obj, id, Qundef);
+
+    if (iv == Qundef) {
+	if (RTEST(ruby_verbose))
+	    rb_warning("instance variable %"PRIsVALUE" not initialized", QUOTE_ID(id));
+	iv = Qnil;
+    }
+    return iv;
+}
+
+VALUE
+rb_attr_get(VALUE obj, ID id)
+{
+    return rb_ivar_lookup(obj, id, Qnil);
+}
+
+VALUE
+rb_ivar_set(VALUE obj, ID id, VALUE val)
+{
+    struct st_table *iv_index_tbl;
+    st_data_t index;
+    long i, len;
+    int ivar_extended;
+
+    rb_check_frozen(obj);
+    if (SPECIAL_CONST_P(obj)) goto generic;
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+        iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
+        if (!iv_index_tbl) {
+            VALUE klass = rb_obj_class(obj);
+            iv_index_tbl = RCLASS_IV_INDEX_TBL(klass);
+            if (!iv_index_tbl) {
+                iv_index_tbl = RCLASS_IV_INDEX_TBL(klass) = st_init_numtable();
+            }
+        }
+        ivar_extended = 0;
+        if (!st_lookup(iv_index_tbl, (st_data_t)id, &index)) {
+            index = iv_index_tbl->num_entries;
+	    if (index >= INT_MAX) rb_raise(rb_eArgError, "too many instance variables");
+            st_add_direct(iv_index_tbl, (st_data_t)id, index);
+            ivar_extended = 1;
+        }
+        len = ROBJECT_NUMIV(obj);
+        if (len <= (long)index) {
+            VALUE *ptr = ROBJECT_IVPTR(obj);
+            if (index < ROBJECT_EMBED_LEN_MAX) {
+                RBASIC(obj)->flags |= ROBJECT_EMBED;
+                ptr = ROBJECT(obj)->as.ary;
+                for (i = 0; i < ROBJECT_EMBED_LEN_MAX; i++) {
+                    ptr[i] = Qundef;
+                }
+            }
+            else {
+                VALUE *newptr;
+                long newsize = (index+1) + (index+1)/4; /* (index+1)*1.25 */
+                if (!ivar_extended &&
+                    iv_index_tbl->num_entries < (st_index_t)newsize) {
+                    newsize = iv_index_tbl->num_entries;
+                }
+
+                if (RBASIC(obj)->flags & ROBJECT_EMBED) {
+                    newptr = ALLOC_N(VALUE, newsize);
+                    MEMCPY(newptr, ptr, VALUE, len);
+                    RBASIC(obj)->flags &= ~ROBJECT_EMBED;
+                    ROBJECT(obj)->as.heap.ivptr = newptr;
+                }
+                else {
+                    REALLOC_N(ROBJECT(obj)->as.heap.ivptr, VALUE, newsize);
+                    newptr = ROBJECT(obj)->as.heap.ivptr;
+                }
+                for (; len < newsize; len++)
+                    newptr[len] = Qundef;
+                ROBJECT(obj)->as.heap.numiv = newsize;
+                ROBJECT(obj)->as.heap.iv_index_tbl = iv_index_tbl;
+            }
+        }
+        RB_OBJ_WRITE(obj, &ROBJECT_IVPTR(obj)[index], val);
+	break;
+      case T_CLASS:
+      case T_MODULE:
+	if (!RCLASS_IV_TBL(obj)) RCLASS_IV_TBL(obj) = st_init_numtable();
+	rb_st_insert_id_and_value(obj, RCLASS_IV_TBL(obj), (st_data_t)id, val);
+        break;
+      default:
+      generic:
+	generic_ivar_set(obj, id, val);
+	break;
+    }
+    return val;
+}
+
+VALUE
+rb_ivar_defined(VALUE obj, ID id)
+{
+    VALUE val;
+    struct st_table *iv_index_tbl;
+    st_data_t index;
+    if (SPECIAL_CONST_P(obj)) goto generic;
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+        iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
+        if (!iv_index_tbl) break;
+        if (!st_lookup(iv_index_tbl, (st_data_t)id, &index)) break;
+        if (ROBJECT_NUMIV(obj) <= (long)index) break;
+        val = ROBJECT_IVPTR(obj)[index];
+        if (val != Qundef)
+            return Qtrue;
+	break;
+      case T_CLASS:
+      case T_MODULE:
+	if (RCLASS_IV_TBL(obj) && st_lookup(RCLASS_IV_TBL(obj), (st_data_t)id, 0))
+	    return Qtrue;
+	break;
+      default:
+      generic:
+	if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj))
+	    return generic_ivar_defined(obj, id);
+	break;
+    }
+    return Qfalse;
+}
+
+struct obj_ivar_tag {
+    VALUE obj;
+    int (*func)(ID key, VALUE val, st_data_t arg);
+    st_data_t arg;
+};
+
+static int
+obj_ivar_i(st_data_t key, st_data_t index, st_data_t arg)
+{
+    struct obj_ivar_tag *data = (struct obj_ivar_tag *)arg;
+    if ((long)index < ROBJECT_NUMIV(data->obj)) {
+        VALUE val = ROBJECT_IVPTR(data->obj)[(long)index];
+        if (val != Qundef) {
+            return (data->func)((ID)key, val, data->arg);
+        }
+    }
+    return ST_CONTINUE;
+}
+
+static void
+obj_ivar_each(VALUE obj, int (*func)(ANYARGS), st_data_t arg)
+{
+    st_table *tbl;
+    struct obj_ivar_tag data;
+
+    tbl = ROBJECT_IV_INDEX_TBL(obj);
+    if (!tbl)
+        return;
+
+    data.obj = obj;
+    data.func = (int (*)(ID key, VALUE val, st_data_t arg))func;
+    data.arg = arg;
+
+    st_foreach_safe(tbl, obj_ivar_i, (st_data_t)&data);
+}
+
+void
+rb_ivar_foreach(VALUE obj, int (*func)(ANYARGS), st_data_t arg)
+{
+    if (SPECIAL_CONST_P(obj)) goto generic;
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+        obj_ivar_each(obj, func, arg);
+	break;
+      case T_CLASS:
+      case T_MODULE:
+	if (RCLASS_IV_TBL(obj)) {
+	    st_foreach_safe(RCLASS_IV_TBL(obj), func, arg);
+	}
+	break;
+      default:
+      generic:
+	if (!generic_iv_tbl) break;
+	if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj)) {
+	    st_data_t tbl;
+
+	    if (st_lookup(generic_iv_tbl, (st_data_t)obj, &tbl)) {
+		st_foreach_safe((st_table *)tbl, func, arg);
+	    }
+	}
+	break;
+    }
+}
+
+st_index_t
+rb_ivar_count(VALUE obj)
+{
+    st_table *tbl;
+    if (SPECIAL_CONST_P(obj)) goto generic;
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+	if ((tbl = ROBJECT_IV_INDEX_TBL(obj)) != 0) {
+	    st_index_t i, count, num = tbl->num_entries;
+	    const VALUE *const ivptr = ROBJECT_IVPTR(obj);
+	    for (i = count = 0; i < num; ++i) {
+		if (ivptr[i] != Qundef) {
+		    count++;
+		}
+	    }
+	    return count;
+	}
+	break;
+      case T_CLASS:
+      case T_MODULE:
+	if ((tbl = RCLASS_IV_TBL(obj)) != 0) {
+	    return tbl->num_entries;
+	}
+	break;
+      default:
+      generic:
+	if (!generic_iv_tbl) break;
+	if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj)) {
+	    st_data_t data;
+
+	    if (st_lookup(generic_iv_tbl, (st_data_t)obj, &data) &&
+		(tbl = (st_table *)data) != 0) {
+		return tbl->num_entries;
+	    }
+	}
+	break;
+    }
+    return 0;
+}
+
+static int
+ivar_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    ID key = (ID)k;
+    VALUE ary = (VALUE)a;
+
+    if (rb_is_instance_id(key)) {
+	rb_ary_push(ary, ID2SYM(key));
+    }
+    return ST_CONTINUE;
+}
+
+/*
+ *  call-seq:
+ *     obj.instance_variables    -> array
+ *
+ *  Returns an array of instance variable names for the receiver. Note
+ *  that simply defining an accessor does not create the corresponding
+ *  instance variable.
+ *
+ *     class Fred
+ *       attr_accessor :a1
+ *       def initialize
+ *         @iv = 3
+ *       end
+ *     end
+ *     Fred.new.instance_variables   #=> [:@iv]
+ */
+
+VALUE
+rb_obj_instance_variables(VALUE obj)
+{
+    VALUE ary;
+
+    ary = rb_ary_new();
+    rb_ivar_foreach(obj, ivar_i, ary);
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     obj.remove_instance_variable(symbol)    -> obj
+ *
+ *  Removes the named instance variable from <i>obj</i>, returning that
+ *  variable's value.
+ *
+ *     class Dummy
+ *       attr_reader :var
+ *       def initialize
+ *         @var = 99
+ *       end
+ *       def remove
+ *         remove_instance_variable(:@var)
+ *       end
+ *     end
+ *     d = Dummy.new
+ *     d.var      #=> 99
+ *     d.remove   #=> 99
+ *     d.var      #=> nil
+ */
+
+VALUE
+rb_obj_remove_instance_variable(VALUE obj, VALUE name)
+{
+    VALUE val = Qnil;
+    const ID id = rb_check_id(&name);
+    st_data_t n, v;
+    struct st_table *iv_index_tbl;
+    st_data_t index;
+
+    rb_check_frozen(obj);
+    if (!id) {
+	if (rb_is_instance_name(name)) {
+	    rb_name_error_str(name, "instance variable %"PRIsVALUE" not defined",
+			      name);
+	}
+	else {
+	    rb_name_error_str(name, "`%"PRIsVALUE"' is not allowed as an instance variable name",
+			      QUOTE(name));
+	}
+    }
+    if (!rb_is_instance_id(id)) {
+	rb_name_error(id, "`%"PRIsVALUE"' is not allowed as an instance variable name",
+		      QUOTE_ID(id));
+    }
+
+    if (SPECIAL_CONST_P(obj)) goto generic;
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+        iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
+        if (!iv_index_tbl) break;
+        if (!st_lookup(iv_index_tbl, (st_data_t)id, &index)) break;
+        if (ROBJECT_NUMIV(obj) <= (long)index) break;
+        val = ROBJECT_IVPTR(obj)[index];
+        if (val != Qundef) {
+            ROBJECT_IVPTR(obj)[index] = Qundef;
+            return val;
+        }
+	break;
+      case T_CLASS:
+      case T_MODULE:
+	n = id;
+	if (RCLASS_IV_TBL(obj) && st_delete(RCLASS_IV_TBL(obj), &n, &v)) {
+	    return (VALUE)v;
+	}
+	break;
+      default:
+      generic:
+	if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj)) {
+	    v = val;
+	    if (generic_ivar_remove(obj, (st_data_t)id, &v)) {
+		return (VALUE)v;
+	    }
+	}
+	break;
+    }
+    rb_name_error(id, "instance variable %"PRIsVALUE" not defined", QUOTE_ID(id));
+
+    UNREACHABLE;
+}
+
+NORETURN(static void uninitialized_constant(VALUE, VALUE));
+static void
+uninitialized_constant(VALUE klass, VALUE name)
+{
+    if (klass && rb_class_real(klass) != rb_cObject)
+	rb_name_error_str(name, "uninitialized constant %"PRIsVALUE"::% "PRIsVALUE"",
+			  rb_class_name(klass), name);
+    else {
+	rb_name_error_str(name, "uninitialized constant % "PRIsVALUE"", name);
+    }
+}
+
+VALUE
+rb_const_missing(VALUE klass, VALUE name)
+{
+    VALUE value = rb_funcallv(klass, rb_intern("const_missing"), 1, &name);
+    rb_vm_inc_const_missing_count();
+    return value;
+}
+
+
+/*
+ * call-seq:
+ *    mod.const_missing(sym)    -> obj
+ *
+ * Invoked when a reference is made to an undefined constant in
+ * <i>mod</i>. It is passed a symbol for the undefined constant, and
+ * returns a value to be used for that constant. The
+ * following code is an example of the same:
+ *
+ *   def Foo.const_missing(name)
+ *     name # return the constant name as Symbol
+ *   end
+ *
+ *   Foo::UNDEFINED_CONST    #=> :UNDEFINED_CONST: symbol returned
+ *
+ * In the next example when a reference is made to an undefined constant,
+ * it attempts to load a file whose name is the lowercase version of the
+ * constant (thus class <code>Fred</code> is assumed to be in file
+ * <code>fred.rb</code>).  If found, it returns the loaded class. It
+ * therefore implements an autoload feature similar to Kernel#autoload and
+ * Module#autoload.
+ *
+ *   def Object.const_missing(name)
+ *     @looked_for ||= {}
+ *     str_name = name.to_s
+ *     raise "Class not found: #{name}" if @looked_for[str_name]
+ *     @looked_for[str_name] = 1
+ *     file = str_name.downcase
+ *     require file
+ *     klass = const_get(name)
+ *     return klass if klass
+ *     raise "Class not found: #{name}"
+ *   end
+ *
+ */
+
+VALUE
+rb_mod_const_missing(VALUE klass, VALUE name)
+{
+    rb_vm_pop_cfunc_frame();
+    uninitialized_constant(klass, name);
+
+    UNREACHABLE;
+}
+
+static void
+autoload_mark(void *ptr)
+{
+    rb_mark_tbl((st_table *)ptr);
+}
+
+static void
+autoload_free(void *ptr)
+{
+    st_free_table((st_table *)ptr);
+}
+
+static size_t
+autoload_memsize(const void *ptr)
+{
+    const st_table *tbl = ptr;
+    return st_memsize(tbl);
+}
+
+static const rb_data_type_t autoload_data_type = {
+    "autoload",
+    {autoload_mark, autoload_free, autoload_memsize,},
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+#define check_autoload_table(av) \
+    (struct st_table *)rb_check_typeddata((av), &autoload_data_type)
+
+static VALUE
+autoload_data(VALUE mod, ID id)
+{
+    struct st_table *tbl;
+    st_data_t val;
+
+    if (!st_lookup(RCLASS_IV_TBL(mod), autoload, &val) ||
+	    !(tbl = check_autoload_table((VALUE)val)) || !st_lookup(tbl, (st_data_t)id, &val)) {
+	return 0;
+    }
+    return (VALUE)val;
+}
+
+struct autoload_data_i {
+    VALUE feature;
+    int safe_level;
+    VALUE thread;
+    VALUE value;
+};
+
+static void
+autoload_i_mark(void *ptr)
+{
+    struct autoload_data_i *p = ptr;
+    rb_gc_mark(p->feature);
+    rb_gc_mark(p->thread);
+    rb_gc_mark(p->value);
+}
+
+static size_t
+autoload_i_memsize(const void *ptr)
+{
+    return sizeof(struct autoload_data_i);
+}
+
+static const rb_data_type_t autoload_data_i_type = {
+    "autoload_i",
+    {autoload_i_mark, RUBY_TYPED_DEFAULT_FREE, autoload_i_memsize,},
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+#define check_autoload_data(av) \
+    (struct autoload_data_i *)rb_check_typeddata((av), &autoload_data_i_type)
+
+void
+rb_autoload(VALUE mod, ID id, const char *file)
+{
+    st_data_t av;
+    VALUE ad, fn;
+    struct st_table *tbl;
+    struct autoload_data_i *ele;
+    rb_const_entry_t *ce;
+
+    if (!rb_is_const_id(id)) {
+	rb_raise(rb_eNameError, "autoload must be constant name: %"PRIsVALUE"",
+		 QUOTE_ID(id));
+    }
+    if (!file || !*file) {
+	rb_raise(rb_eArgError, "empty file name");
+    }
+
+    ce = rb_const_lookup(mod, id);
+    if (ce && ce->value != Qundef) {
+	return;
+    }
+
+    rb_const_set(mod, id, Qundef);
+    tbl = RCLASS_IV_TBL(mod);
+    if (tbl && st_lookup(tbl, (st_data_t)autoload, &av)) {
+	tbl = check_autoload_table((VALUE)av);
+    }
+    else {
+	if (!tbl) tbl = RCLASS_IV_TBL(mod) = st_init_numtable();
+	av = (st_data_t)TypedData_Wrap_Struct(0, &autoload_data_type, 0);
+	st_add_direct(tbl, (st_data_t)autoload, av);
+	RB_OBJ_WRITTEN(mod, Qnil, av);
+	DATA_PTR(av) = tbl = st_init_numtable();
+    }
+    fn = rb_str_new2(file);
+    FL_UNSET(fn, FL_TAINT);
+    OBJ_FREEZE(fn);
+
+    ele = ALLOC(struct autoload_data_i);
+    ele->feature = fn;
+    ele->safe_level = rb_safe_level();
+    ele->thread = Qnil;
+    ele->value = Qundef;
+    ad = TypedData_Wrap_Struct(0, &autoload_data_i_type, ele);
+    st_insert(tbl, (st_data_t)id, (st_data_t)ad);
+}
+
+static void
+autoload_delete(VALUE mod, ID id)
+{
+    st_data_t val, load = 0, n = id;
+    rb_const_entry_t *ce;
+
+    st_delete(RCLASS_CONST_TBL(mod), &n, &val);
+    ce = (rb_const_entry_t*)val;
+    if (ce) xfree(ce);
+    if (st_lookup(RCLASS_IV_TBL(mod), (st_data_t)autoload, &val)) {
+	struct st_table *tbl = check_autoload_table((VALUE)val);
+
+	st_delete(tbl, &n, &load);
+
+	if (tbl->num_entries == 0) {
+	    n = autoload;
+	    st_delete(RCLASS_IV_TBL(mod), &n, &val);
+	}
+    }
+}
+
+static VALUE
+autoload_provided(VALUE arg)
+{
+    const char **p = (const char **)arg;
+    return rb_feature_provided(*p, p);
+}
+
+static VALUE
+reset_safe(VALUE safe)
+{
+    rb_set_safe_level_force((int)safe);
+    return safe;
+}
+
+static VALUE
+check_autoload_required(VALUE mod, ID id, const char **loadingpath)
+{
+    VALUE file, load;
+    struct autoload_data_i *ele;
+    const char *loading;
+    int safe;
+
+    if (!(load = autoload_data(mod, id)) || !(ele = check_autoload_data(load))) {
+	return 0;
+    }
+    file = ele->feature;
+    Check_Type(file, T_STRING);
+    if (!RSTRING_PTR(file) || !*RSTRING_PTR(file)) {
+	rb_raise(rb_eArgError, "empty file name");
+    }
+    loading = RSTRING_PTR(file);
+    safe = rb_safe_level();
+    rb_set_safe_level_force(0);
+    if (!rb_ensure(autoload_provided, (VALUE)&loading, reset_safe, (VALUE)safe)) {
+	return load;
+    }
+    if (loadingpath && loading) {
+	*loadingpath = loading;
+	return load;
+    }
+    return 0;
+}
+
+int
+rb_autoloading_value(VALUE mod, ID id, VALUE* value)
+{
+    VALUE load;
+    struct autoload_data_i *ele;
+
+    if (!(load = autoload_data(mod, id)) || !(ele = check_autoload_data(load))) {
+	return 0;
+    }
+    if (ele->thread == rb_thread_current()) {
+	if (ele->value != Qundef) {
+	    if (value) {
+		*value = ele->value;
+	    }
+	    return 1;
+	}
+    }
+    return 0;
+}
+
+static int
+autoload_defined_p(VALUE mod, ID id)
+{
+    rb_const_entry_t *ce = rb_const_lookup(mod, id);
+
+    if (!ce || ce->value != Qundef) {
+	return 0;
+    }
+    return !rb_autoloading_value(mod, id, NULL);
+}
+
+struct autoload_const_set_args {
+    VALUE mod;
+    ID id;
+    VALUE value;
+};
+
+static VALUE
+autoload_const_set(VALUE arg)
+{
+    struct autoload_const_set_args* args = (struct autoload_const_set_args *)arg;
+    autoload_delete(args->mod, args->id);
+    rb_const_set(args->mod, args->id, args->value);
+    return 0;			/* ignored */
+}
+
+static VALUE
+autoload_require(VALUE arg)
+{
+    struct autoload_data_i *ele = (struct autoload_data_i *)arg;
+    return rb_require_safe(ele->feature, ele->safe_level);
+}
+
+VALUE
+rb_autoload_load(VALUE mod, ID id)
+{
+    VALUE load, result;
+    const char *loading = 0, *src;
+    struct autoload_data_i *ele;
+    int state = 0;
+
+    if (!autoload_defined_p(mod, id)) return Qfalse;
+    load = check_autoload_required(mod, id, &loading);
+    if (!load) return Qfalse;
+    src = rb_sourcefile();
+    if (src && loading && strcmp(src, loading) == 0) return Qfalse;
+
+    /* set ele->thread for a marker of autoloading thread */
+    if (!(ele = check_autoload_data(load))) {
+	return Qfalse;
+    }
+    if (ele->thread == Qnil) {
+	ele->thread = rb_thread_current();
+    }
+    /* autoload_data_i can be deleted by another thread while require */
+    result = rb_protect(autoload_require, (VALUE)ele, &state);
+    if (ele->thread == rb_thread_current()) {
+	ele->thread = Qnil;
+    }
+    if (state) rb_jump_tag(state);
+
+    if (RTEST(result)) {
+	/* At the last, move a value defined in autoload to constant table */
+	if (ele->value != Qundef) {
+	    int safe_backup;
+	    struct autoload_const_set_args args;
+	    args.mod = mod;
+	    args.id = id;
+	    args.value = ele->value;
+	    safe_backup = rb_safe_level();
+	    rb_set_safe_level_force(ele->safe_level);
+	    rb_ensure(autoload_const_set, (VALUE)&args, reset_safe, (VALUE)safe_backup);
+	}
+    }
+    RB_GC_GUARD(load);
+    return result;
+}
+
+VALUE
+rb_autoload_p(VALUE mod, ID id)
+{
+    VALUE load;
+    struct autoload_data_i *ele;
+
+    while (!autoload_defined_p(mod, id)) {
+	mod = RCLASS_SUPER(mod);
+	if (!mod) return Qnil;
+    }
+    load = check_autoload_required(mod, id, 0);
+    if (!load) return Qnil;
+    return (ele = check_autoload_data(load)) ? ele->feature : Qnil;
+}
+
+static VALUE
+rb_const_get_0(VALUE klass, ID id, int exclude, int recurse, int visibility)
+{
+    VALUE value, tmp, av;
+    int mod_retry = 0;
+
+    tmp = klass;
+  retry:
+    while (RTEST(tmp)) {
+	VALUE am = 0;
+	rb_const_entry_t *ce;
+
+	while ((ce = rb_const_lookup(tmp, id))) {
+	    if (visibility && RB_CONST_PRIVATE_P(ce)) {
+		rb_name_error(id, "private constant %"PRIsVALUE"::%"PRIsVALUE" referenced",
+			      rb_class_name(klass), QUOTE_ID(id));
+	    }
+	    value = ce->value;
+	    if (value == Qundef) {
+		if (am == tmp) break;
+		am = tmp;
+		if (rb_autoloading_value(tmp, id, &av)) return av;
+		rb_autoload_load(tmp, id);
+		continue;
+	    }
+	    if (exclude && tmp == rb_cObject && klass != rb_cObject) {
+		rb_warn("toplevel constant %"PRIsVALUE" referenced by %"PRIsVALUE"::%"PRIsVALUE"",
+			QUOTE_ID(id), rb_class_name(klass), QUOTE_ID(id));
+	    }
+	    return value;
+	}
+	if (!recurse) break;
+	tmp = RCLASS_SUPER(tmp);
+    }
+    if (!exclude && !mod_retry && BUILTIN_TYPE(klass) == T_MODULE) {
+	mod_retry = 1;
+	tmp = rb_cObject;
+	goto retry;
+    }
+
+    return rb_const_missing(klass, ID2SYM(id));
+}
+
+VALUE
+rb_const_get_from(VALUE klass, ID id)
+{
+    return rb_const_get_0(klass, id, TRUE, TRUE, FALSE);
+}
+
+VALUE
+rb_const_get(VALUE klass, ID id)
+{
+    return rb_const_get_0(klass, id, FALSE, TRUE, FALSE);
+}
+
+VALUE
+rb_const_get_at(VALUE klass, ID id)
+{
+    return rb_const_get_0(klass, id, TRUE, FALSE, FALSE);
+}
+
+VALUE
+rb_public_const_get_from(VALUE klass, ID id)
+{
+    return rb_const_get_0(klass, id, TRUE, TRUE, TRUE);
+}
+
+VALUE
+rb_public_const_get(VALUE klass, ID id)
+{
+    return rb_const_get_0(klass, id, FALSE, TRUE, TRUE);
+}
+
+VALUE
+rb_public_const_get_at(VALUE klass, ID id)
+{
+    return rb_const_get_0(klass, id, TRUE, FALSE, TRUE);
+}
+
+/*
+ *  call-seq:
+ *     remove_const(sym)   -> obj
+ *
+ *  Removes the definition of the given constant, returning that
+ *  constant's previous value.  If that constant referred to
+ *  a module, this will not change that module's name and can lead
+ *  to confusion.
+ */
+
+VALUE
+rb_mod_remove_const(VALUE mod, VALUE name)
+{
+    const ID id = rb_check_id(&name);
+
+    if (!id) {
+	if (rb_is_const_name(name)) {
+	    rb_name_error_str(name, "constant %"PRIsVALUE"::%"PRIsVALUE" not defined",
+			      rb_class_name(mod), name);
+	}
+	else {
+	    rb_name_error_str(name, "`%"PRIsVALUE"' is not allowed as a constant name",
+			      QUOTE(name));
+	}
+    }
+    if (!rb_is_const_id(id)) {
+	rb_name_error(id, "`%"PRIsVALUE"' is not allowed as a constant name",
+		      QUOTE_ID(id));
+    }
+    return rb_const_remove(mod, id);
+}
+
+VALUE
+rb_const_remove(VALUE mod, ID id)
+{
+    VALUE val;
+    st_data_t v, n = id;
+
+    rb_check_frozen(mod);
+    if (!RCLASS_CONST_TBL(mod) || !st_delete(RCLASS_CONST_TBL(mod), &n, &v)) {
+	if (rb_const_defined_at(mod, id)) {
+	    rb_name_error(id, "cannot remove %"PRIsVALUE"::%"PRIsVALUE"",
+			  rb_class_name(mod), QUOTE_ID(id));
+	}
+	rb_name_error(id, "constant %"PRIsVALUE"::%"PRIsVALUE" not defined",
+		      rb_class_name(mod), QUOTE_ID(id));
+    }
+
+    rb_clear_constant_cache();
+
+    val = ((rb_const_entry_t*)v)->value;
+    if (val == Qundef) {
+	autoload_delete(mod, id);
+	val = Qnil;
+    }
+    xfree((rb_const_entry_t*)v);
+    return val;
+}
+
+static int
+cv_i_update(st_data_t *k, st_data_t *v, st_data_t a, int existing)
+{
+    if (existing) return ST_STOP;
+    *v = a;
+    return ST_CONTINUE;
+}
+
+static int
+sv_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    ID key = (ID)k;
+    rb_const_entry_t *ce = (rb_const_entry_t *)v;
+    st_table *tbl = (st_table *)a;
+
+    if (rb_is_const_id(key)) {
+	st_update(tbl, (st_data_t)key, cv_i_update, (st_data_t)ce);
+    }
+    return ST_CONTINUE;
+}
+
+static int
+rb_local_constants_i(st_data_t const_name, st_data_t const_value, st_data_t ary)
+{
+    rb_ary_push((VALUE)ary, ID2SYM((ID)const_name));
+    return ST_CONTINUE;
+}
+
+static VALUE
+rb_local_constants(VALUE mod)
+{
+    st_table *tbl = RCLASS_CONST_TBL(mod);
+    VALUE ary;
+
+    if (!tbl) return rb_ary_new2(0);
+
+    ary = rb_ary_new2(tbl->num_entries);
+    st_foreach(tbl, rb_local_constants_i, ary);
+    return ary;
+}
+
+void*
+rb_mod_const_at(VALUE mod, void *data)
+{
+    st_table *tbl = data;
+    if (!tbl) {
+	tbl = st_init_numtable();
+    }
+    if (RCLASS_CONST_TBL(mod)) {
+	st_foreach_safe(RCLASS_CONST_TBL(mod), sv_i, (st_data_t)tbl);
+    }
+    return tbl;
+}
+
+void*
+rb_mod_const_of(VALUE mod, void *data)
+{
+    VALUE tmp = mod;
+    for (;;) {
+	data = rb_mod_const_at(tmp, data);
+	tmp = RCLASS_SUPER(tmp);
+	if (!tmp) break;
+	if (tmp == rb_cObject && mod != rb_cObject) break;
+    }
+    return data;
+}
+
+static int
+list_i(st_data_t key, st_data_t value, VALUE ary)
+{
+    ID sym = (ID)key;
+    rb_const_entry_t *ce = (rb_const_entry_t *)value;
+    if (RB_CONST_PUBLIC_P(ce)) rb_ary_push(ary, ID2SYM(sym));
+    return ST_CONTINUE;
+}
+
+VALUE
+rb_const_list(void *data)
+{
+    st_table *tbl = data;
+    VALUE ary;
+
+    if (!tbl) return rb_ary_new2(0);
+    ary = rb_ary_new2(tbl->num_entries);
+    st_foreach_safe(tbl, list_i, ary);
+    st_free_table(tbl);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     mod.constants(inherit=true)    -> array
+ *
+ *  Returns an array of the names of the constants accessible in
+ *  <i>mod</i>. This includes the names of constants in any included
+ *  modules (example at start of section), unless the <i>inherit</i>
+ *  parameter is set to <code>false</code>.
+ *
+ *    IO.constants.include?(:SYNC)        #=> true
+ *    IO.constants(false).include?(:SYNC) #=> false
+ *
+ *  Also see <code>Module::const_defined?</code>.
+ */
+
+VALUE
+rb_mod_constants(int argc, const VALUE *argv, VALUE mod)
+{
+    VALUE inherit;
+
+    if (argc == 0) {
+	inherit = Qtrue;
+    }
+    else {
+	rb_scan_args(argc, argv, "01", &inherit);
+    }
+
+    if (RTEST(inherit)) {
+	return rb_const_list(rb_mod_const_of(mod, 0));
+    }
+    else {
+	return rb_local_constants(mod);
+    }
+}
+
+static int
+rb_const_defined_0(VALUE klass, ID id, int exclude, int recurse, int visibility)
+{
+    VALUE tmp;
+    int mod_retry = 0;
+    rb_const_entry_t *ce;
+
+    tmp = klass;
+  retry:
+    while (tmp) {
+	if ((ce = rb_const_lookup(tmp, id))) {
+	    if (visibility && RB_CONST_PRIVATE_P(ce)) {
+		return (int)Qfalse;
+	    }
+	    if (ce->value == Qundef && !check_autoload_required(tmp, id, 0) && !rb_autoloading_value(tmp, id, 0))
+		return (int)Qfalse;
+	    return (int)Qtrue;
+	}
+	if (!recurse) break;
+	tmp = RCLASS_SUPER(tmp);
+    }
+    if (!exclude && !mod_retry && BUILTIN_TYPE(klass) == T_MODULE) {
+	mod_retry = 1;
+	tmp = rb_cObject;
+	goto retry;
+    }
+    return (int)Qfalse;
+}
+
+int
+rb_const_defined_from(VALUE klass, ID id)
+{
+    return rb_const_defined_0(klass, id, TRUE, TRUE, FALSE);
+}
+
+int
+rb_const_defined(VALUE klass, ID id)
+{
+    return rb_const_defined_0(klass, id, FALSE, TRUE, FALSE);
+}
+
+int
+rb_const_defined_at(VALUE klass, ID id)
+{
+    return rb_const_defined_0(klass, id, TRUE, FALSE, FALSE);
+}
+
+int
+rb_public_const_defined_from(VALUE klass, ID id)
+{
+    return rb_const_defined_0(klass, id, TRUE, TRUE, TRUE);
+}
+
+int
+rb_public_const_defined(VALUE klass, ID id)
+{
+    return rb_const_defined_0(klass, id, FALSE, TRUE, TRUE);
+}
+
+int
+rb_public_const_defined_at(VALUE klass, ID id)
+{
+    return rb_const_defined_0(klass, id, TRUE, FALSE, TRUE);
+}
+
+static void
+check_before_mod_set(VALUE klass, ID id, VALUE val, const char *dest)
+{
+    rb_check_frozen(klass);
+}
+
+void
+rb_const_set(VALUE klass, ID id, VALUE val)
+{
+    rb_const_entry_t *ce;
+    rb_const_flag_t visibility = CONST_PUBLIC;
+
+    if (NIL_P(klass)) {
+	rb_raise(rb_eTypeError, "no class/module to define constant %"PRIsVALUE"",
+		 QUOTE_ID(id));
+    }
+
+    check_before_mod_set(klass, id, val, "constant");
+    if (!RCLASS_CONST_TBL(klass)) {
+	RCLASS_CONST_TBL(klass) = st_init_numtable();
+    }
+    else {
+	ce = rb_const_lookup(klass, id);
+	if (ce) {
+	    if (ce->value == Qundef) {
+		VALUE load;
+		struct autoload_data_i *ele;
+
+		load = autoload_data(klass, id);
+		/* for autoloading thread, keep the defined value to autoloading storage */
+		if (load && (ele = check_autoload_data(load)) && (ele->thread == rb_thread_current())) {
+		    rb_clear_constant_cache();
+
+		    ele->value = val; /* autoload_i is non-WB-protected */
+		    return;
+		}
+		/* otherwise, allow to override */
+		autoload_delete(klass, id);
+	    }
+	    else {
+		VALUE name = QUOTE_ID(id);
+		visibility = ce->flag;
+		if (klass == rb_cObject)
+		    rb_warn("already initialized constant %"PRIsVALUE"", name);
+		else
+		    rb_warn("already initialized constant %"PRIsVALUE"::%"PRIsVALUE"",
+			    rb_class_name(klass), name);
+		if (!NIL_P(ce->file) && ce->line) {
+		    rb_compile_warn(RSTRING_PTR(ce->file), ce->line,
+				    "previous definition of %"PRIsVALUE" was here", name);
+		}
+		st_delete(RCLASS_CONST_TBL(klass), &id, 0);
+		xfree(ce);
+	    }
+	}
+    }
+
+    rb_clear_constant_cache();
+
+
+    ce = ZALLOC(rb_const_entry_t);
+    ce->flag = visibility;
+    ce->line = rb_sourceline();
+    st_insert(RCLASS_CONST_TBL(klass), (st_data_t)id, (st_data_t)ce);
+    RB_OBJ_WRITE(klass, &ce->value, val);
+    RB_OBJ_WRITE(klass, &ce->file, rb_sourcefilename());
+}
+
+void
+rb_define_const(VALUE klass, const char *name, VALUE val)
+{
+    ID id = rb_intern(name);
+
+    if (!rb_is_const_id(id)) {
+	rb_warn("rb_define_const: invalid name `%s' for constant", name);
+    }
+    rb_const_set(klass, id, val);
+}
+
+void
+rb_define_global_const(const char *name, VALUE val)
+{
+    rb_define_const(rb_cObject, name, val);
+}
+
+static void
+set_const_visibility(VALUE mod, int argc, const VALUE *argv, rb_const_flag_t flag)
+{
+    int i;
+    rb_const_entry_t *ce;
+    ID id;
+
+    if (argc == 0) {
+	rb_warning("%"PRIsVALUE" with no argument is just ignored",
+		   QUOTE_ID(rb_frame_callee()));
+	return;
+    }
+
+    for (i = 0; i < argc; i++) {
+	VALUE val = argv[i];
+	id = rb_check_id(&val);
+	if (!id) {
+	    if (i > 0) {
+		rb_clear_constant_cache();
+	    }
+
+	    rb_name_error_str(val, "constant %"PRIsVALUE"::%"PRIsVALUE" not defined",
+			      rb_class_name(mod), QUOTE(val));
+	}
+	if ((ce = rb_const_lookup(mod, id))) {
+	    ce->flag = flag;
+	}
+	else {
+	    if (i > 0) {
+		rb_clear_constant_cache();
+	    }
+	    rb_name_error(id, "constant %"PRIsVALUE"::%"PRIsVALUE" not defined",
+			  rb_class_name(mod), QUOTE_ID(id));
+	}
+    }
+    rb_clear_constant_cache();
+}
+
+/*
+ *  call-seq:
+ *     mod.private_constant(symbol, ...)    => mod
+ *
+ *  Makes a list of existing constants private.
+ */
+
+VALUE
+rb_mod_private_constant(int argc, const VALUE *argv, VALUE obj)
+{
+    set_const_visibility(obj, argc, argv, CONST_PRIVATE);
+    return obj;
+}
+
+/*
+ *  call-seq:
+ *     mod.public_constant(symbol, ...)    => mod
+ *
+ *  Makes a list of existing constants public.
+ */
+
+VALUE
+rb_mod_public_constant(int argc, const VALUE *argv, VALUE obj)
+{
+    set_const_visibility(obj, argc, argv, CONST_PUBLIC);
+    return obj;
+}
+
+static VALUE
+original_module(VALUE c)
+{
+    if (RB_TYPE_P(c, T_ICLASS))
+	return RBASIC(c)->klass;
+    return c;
+}
+
+static int
+cvar_lookup_at(VALUE klass, ID id, st_data_t *v)
+{
+    if (!RCLASS_IV_TBL(klass)) return 0;
+    return st_lookup(RCLASS_IV_TBL(klass), (st_data_t)id, v);
+}
+
+static VALUE
+cvar_front_klass(VALUE klass)
+{
+    if (FL_TEST(klass, FL_SINGLETON)) {
+	VALUE obj = rb_ivar_get(klass, id__attached__);
+	if (RB_TYPE_P(obj, T_MODULE) || RB_TYPE_P(obj, T_CLASS)) {
+	    return obj;
+	}
+    }
+    return RCLASS_SUPER(klass);
+}
+
+#define CVAR_FOREACH_ANCESTORS(klass, v, r) \
+    for (klass = cvar_front_klass(klass); klass; klass = RCLASS_SUPER(klass)) { \
+	if (cvar_lookup_at(klass, id, (v))) { \
+	    r; \
+	} \
+    }
+
+#define CVAR_LOOKUP(v,r) do {\
+    if (cvar_lookup_at(klass, id, (v))) {r;}\
+    CVAR_FOREACH_ANCESTORS(klass, v, r);\
+} while(0)
+
+void
+rb_cvar_set(VALUE klass, ID id, VALUE val)
+{
+    VALUE tmp, front = 0, target = 0;
+
+    tmp = klass;
+    CVAR_LOOKUP(0, {if (!front) front = klass; target = klass;});
+    if (target) {
+	if (front && target != front) {
+	    st_data_t did = id;
+
+	    if (RTEST(ruby_verbose)) {
+		rb_warning("class variable %"PRIsVALUE" of %"PRIsVALUE" is overtaken by %"PRIsVALUE"",
+			   QUOTE_ID(id), rb_class_name(original_module(front)),
+			   rb_class_name(original_module(target)));
+	    }
+	    if (BUILTIN_TYPE(front) == T_CLASS) {
+		st_delete(RCLASS_IV_TBL(front),&did,0);
+	    }
+	}
+    }
+    else {
+	target = tmp;
+    }
+
+    check_before_mod_set(target, id, val, "class variable");
+    if (!RCLASS_IV_TBL(target)) {
+	RCLASS_IV_TBL(target) = st_init_numtable();
+    }
+
+    rb_st_insert_id_and_value(target, RCLASS_IV_TBL(target), (st_data_t)id, (st_data_t)val);
+}
+
+VALUE
+rb_cvar_get(VALUE klass, ID id)
+{
+    VALUE tmp, front = 0, target = 0;
+    st_data_t value;
+
+    tmp = klass;
+    CVAR_LOOKUP(&value, {if (!front) front = klass; target = klass;});
+    if (!target) {
+	rb_name_error(id, "uninitialized class variable %"PRIsVALUE" in %"PRIsVALUE"",
+		      QUOTE_ID(id), rb_class_name(tmp));
+    }
+    if (front && target != front) {
+	st_data_t did = id;
+
+	if (RTEST(ruby_verbose)) {
+	    rb_warning("class variable %"PRIsVALUE" of %"PRIsVALUE" is overtaken by %"PRIsVALUE"",
+		       QUOTE_ID(id), rb_class_name(original_module(front)),
+		       rb_class_name(original_module(target)));
+	}
+	if (BUILTIN_TYPE(front) == T_CLASS) {
+	    st_delete(RCLASS_IV_TBL(front),&did,0);
+	}
+    }
+    return (VALUE)value;
+}
+
+VALUE
+rb_cvar_defined(VALUE klass, ID id)
+{
+    if (!klass) return Qfalse;
+    CVAR_LOOKUP(0,return Qtrue);
+    return Qfalse;
+}
+
+void
+rb_cv_set(VALUE klass, const char *name, VALUE val)
+{
+    ID id = rb_intern(name);
+    if (!rb_is_class_id(id)) {
+	rb_name_error(id, "wrong class variable name %s", name);
+    }
+    rb_cvar_set(klass, id, val);
+}
+
+VALUE
+rb_cv_get(VALUE klass, const char *name)
+{
+    ID id = rb_intern(name);
+    if (!rb_is_class_id(id)) {
+	rb_name_error(id, "wrong class variable name %s", name);
+    }
+    return rb_cvar_get(klass, id);
+}
+
+void
+rb_define_class_variable(VALUE klass, const char *name, VALUE val)
+{
+    ID id = rb_intern(name);
+
+    if (!rb_is_class_id(id)) {
+	rb_name_error(id, "wrong class variable name %s", name);
+    }
+    rb_cvar_set(klass, id, val);
+}
+
+static int
+cv_i(st_data_t k, st_data_t v, st_data_t a)
+{
+    ID key = (ID)k;
+    st_table *tbl = (st_table *)a;
+
+    if (rb_is_class_id(key)) {
+	st_update(tbl, (st_data_t)key, cv_i_update, 0);
+    }
+    return ST_CONTINUE;
+}
+
+static void*
+mod_cvar_at(VALUE mod, void *data)
+{
+    st_table *tbl = data;
+    if (!tbl) {
+	tbl = st_init_numtable();
+    }
+    if (RCLASS_IV_TBL(mod)) {
+	st_foreach_safe(RCLASS_IV_TBL(mod), cv_i, (st_data_t)tbl);
+    }
+    return tbl;
+}
+
+static void*
+mod_cvar_of(VALUE mod, void *data)
+{
+    VALUE tmp = mod;
+    for (;;) {
+	data = mod_cvar_at(tmp, data);
+	tmp = RCLASS_SUPER(tmp);
+	if (!tmp) break;
+    }
+    return data;
+}
+
+static int
+cv_list_i(st_data_t key, st_data_t value, VALUE ary)
+{
+    ID sym = (ID)key;
+    rb_ary_push(ary, ID2SYM(sym));
+    return ST_CONTINUE;
+}
+
+static VALUE
+cvar_list(void *data)
+{
+    st_table *tbl = data;
+    VALUE ary;
+
+    if (!tbl) return rb_ary_new2(0);
+    ary = rb_ary_new2(tbl->num_entries);
+    st_foreach_safe(tbl, cv_list_i, ary);
+    st_free_table(tbl);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     mod.class_variables(inherit=true)    -> array
+ *
+ *  Returns an array of the names of class variables in <i>mod</i>.
+ *  This includes the names of class variables in any included
+ *  modules, unless the <i>inherit</i> parameter is set to
+ *  <code>false</code>.
+ *
+ *     class One
+ *       @@var1 = 1
+ *     end
+ *     class Two < One
+ *       @@var2 = 2
+ *     end
+ *     One.class_variables          #=> [:@@var1]
+ *     Two.class_variables          #=> [:@@var2, :@@var1]
+ *     Two.class_variables(false)   #=> [:@@var2]
+ */
+
+VALUE
+rb_mod_class_variables(int argc, const VALUE *argv, VALUE mod)
+{
+    VALUE inherit;
+    st_table *tbl;
+
+    if (argc == 0) {
+	inherit = Qtrue;
+    }
+    else {
+	rb_scan_args(argc, argv, "01", &inherit);
+    }
+    if (RTEST(inherit)) {
+	tbl = mod_cvar_of(mod, 0);
+    }
+    else {
+	tbl = mod_cvar_at(mod, 0);
+    }
+    return cvar_list(tbl);
+}
+
+/*
+ *  call-seq:
+ *     remove_class_variable(sym)    -> obj
+ *
+ *  Removes the definition of the <i>sym</i>, returning that
+ *  constant's value.
+ *
+ *     class Dummy
+ *       @@var = 99
+ *       puts @@var
+ *       remove_class_variable(:@@var)
+ *       p(defined? @@var)
+ *     end
+ *
+ *  <em>produces:</em>
+ *
+ *     99
+ *     nil
+ */
+
+VALUE
+rb_mod_remove_cvar(VALUE mod, VALUE name)
+{
+    const ID id = rb_check_id(&name);
+    st_data_t val, n = id;
+
+    if (!id) {
+	if (rb_is_class_name(name)) {
+	    rb_name_error_str(name, "class variable %"PRIsVALUE" not defined for %"PRIsVALUE"",
+			      name, rb_class_name(mod));
+	}
+	else {
+	    rb_name_error_str(name, "wrong class variable name %"PRIsVALUE"", QUOTE(name));
+	}
+    }
+    if (!rb_is_class_id(id)) {
+	rb_name_error(id, "wrong class variable name %"PRIsVALUE"", QUOTE_ID(id));
+    }
+    rb_check_frozen(mod);
+    if (RCLASS_IV_TBL(mod) && st_delete(RCLASS_IV_TBL(mod), &n, &val)) {
+	return (VALUE)val;
+    }
+    if (rb_cvar_defined(mod, id)) {
+	rb_name_error(id, "cannot remove %"PRIsVALUE" for %"PRIsVALUE"",
+		 QUOTE_ID(id), rb_class_name(mod));
+    }
+    rb_name_error(id, "class variable %"PRIsVALUE" not defined for %"PRIsVALUE"",
+		  QUOTE_ID(id), rb_class_name(mod));
+
+    UNREACHABLE;
+}
+
+VALUE
+rb_iv_get(VALUE obj, const char *name)
+{
+    ID id = rb_intern(name);
+
+    return rb_ivar_get(obj, id);
+}
+
+VALUE
+rb_iv_set(VALUE obj, const char *name, VALUE val)
+{
+    ID id = rb_intern(name);
+
+    return rb_ivar_set(obj, id, val);
+}
+
+/* tbl = xx(obj); tbl[key] = value; */
+int
+rb_st_insert_id_and_value(VALUE obj, st_table *tbl, ID key, VALUE value)
+{
+    int result = st_insert(tbl, (st_data_t)key, (st_data_t)value);
+    RB_OBJ_WRITTEN(obj, Qundef, value);
+    return result;
+}
+
+static int
+tbl_copy_i(st_data_t key, st_data_t value, st_data_t data)
+{
+    RB_OBJ_WRITTEN((VALUE)data, Qundef, (VALUE)value);
+    return ST_CONTINUE;
+}
+
+st_table *
+rb_st_copy(VALUE obj, struct st_table *orig_tbl)
+{
+    st_table *new_tbl = st_copy(orig_tbl);
+    st_foreach(new_tbl, tbl_copy_i, (st_data_t)obj);
+    return new_tbl;
+}
+
+rb_const_entry_t *
+rb_const_lookup(VALUE klass, ID id)
+{
+    st_table *tbl = RCLASS_CONST_TBL(klass);
+    st_data_t val;
+
+    if (tbl && st_lookup(tbl, (st_data_t)id, &val)) {
+	return (rb_const_entry_t *)val;
+    }
+    return 0;
+}