variable.c

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

  variable.c -

  $Author: matz $
  $Date: 2005/12/12 00:36:52 $
  created at: Tue Apr 19 23:55:15 JST 1994

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

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

#include "ruby.h"
#include "env.h"
#include "node.h"
#include "st.h"
#include "util.h"

static st_table *rb_global_tbl;
st_table *rb_class_tbl;
static ID autoload, classpath, tmp_classpath;

void
Init_var_tables()
{
    rb_global_tbl = st_init_numtable();
    rb_class_tbl = st_init_numtable();
    autoload = rb_intern("__autoload__");
    classpath = rb_intern("__classpath__");
    tmp_classpath = rb_intern("__tmp_classpath__");
}

struct fc_result {
    ID name;
    VALUE klass;
    VALUE path;
    VALUE track;
    struct fc_result *prev;
};

static VALUE
fc_path(fc, name)
    struct fc_result *fc;
    ID name;
{
    VALUE path, tmp;

    path = rb_str_new2(rb_id2name(name));
    while (fc) {
        if (fc->track == rb_cObject) break;
        if (ROBJECT(fc->track)->iv_tbl &&
            st_lookup(ROBJECT(fc->track)->iv_tbl, classpath, &tmp)) {
            tmp = rb_str_dup(tmp);
            rb_str_cat2(tmp, "::");
            rb_str_append(tmp, path);

            return tmp;
        }
        tmp = rb_str_new2(rb_id2name(fc->name));
        rb_str_cat2(tmp, "::");
        rb_str_append(tmp, path);
        path = tmp;
        fc = fc->prev;
    }
    return path;
}

static int
fc_i(key, value, res)
    ID key;
    VALUE value;
    struct fc_result *res;
{
    if (!rb_is_const_id(key)) return ST_CONTINUE;

    if (value == res->klass) {
        res->path = fc_path(res, key);
        return ST_STOP;
    }
    switch (TYPE(value)) {
      case T_MODULE:
      case T_CLASS:
        if (!RCLASS(value)->iv_tbl) 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.path = 0;
            arg.klass = res->klass;
            arg.track = value;
            arg.prev = res;
            st_foreach_safe(RCLASS(value)->iv_tbl, fc_i, (st_data_t)&arg);
            if (arg.path) {
                res->path = arg.path;
                return ST_STOP;
            }
        }
        break;

      default:
        break;
    }
    return ST_CONTINUE;
}

static VALUE
find_class_path(klass)
    VALUE klass;
{
    struct fc_result arg;

    arg.name = 0;
    arg.path = 0;
    arg.klass = klass;
    arg.track = rb_cObject;
    arg.prev = 0;
    if (RCLASS(rb_cObject)->iv_tbl) {
        st_foreach_safe(RCLASS(rb_cObject)->iv_tbl, fc_i, (st_data_t)&arg);
    }
    if (arg.path == 0) {
        st_foreach(rb_class_tbl, fc_i, (st_data_t)&arg);
    }
    if (arg.path) {
        if (!ROBJECT(klass)->iv_tbl) {
            ROBJECT(klass)->iv_tbl = st_init_numtable();
        }
        st_insert(ROBJECT(klass)->iv_tbl, classpath, arg.path);
        st_delete(RCLASS(klass)->iv_tbl, &tmp_classpath, 0);
        return arg.path;
    }
    return Qnil;
}

static VALUE
classname(klass)
    VALUE klass;
{
    VALUE path = Qnil;

    if (!klass) klass = rb_cObject;
    if (ROBJECT(klass)->iv_tbl) {
        if (!st_lookup(ROBJECT(klass)->iv_tbl, classpath, &path)) {
            ID classid = rb_intern("__classid__");

            if (!st_lookup(ROBJECT(klass)->iv_tbl, classid, &path)) {
                return find_class_path(klass);
            }
            path = rb_str_new2(rb_id2name(SYM2ID(path)));
            st_insert(ROBJECT(klass)->iv_tbl, classpath, path);
            st_delete(RCLASS(klass)->iv_tbl, (st_data_t*)&classid, 0);
        }
        if (TYPE(path) != T_STRING) {
            rb_bug("class path is not set properly");
        }
        return path;
    }
    return find_class_path(klass);
}

/*
 *  call-seq:
 *     mod.name    => string
 *  
 *  Returns the name of the module <i>mod</i>.
 */

VALUE
rb_mod_name(mod)
    VALUE mod;
{
    VALUE path = classname(mod);

    if (!NIL_P(path)) return rb_str_dup(path);
    return rb_str_new(0,0);
}

VALUE
rb_class_path(klass)
    VALUE klass;
{
    VALUE path = classname(klass);

    if (!NIL_P(path)) return path;
    if (RCLASS(klass)->iv_tbl && st_lookup(RCLASS(klass)->iv_tbl,
                                           tmp_classpath, &path)) {
        return path;
    }
    else {
        char *s = "Class";
        size_t len;

        if (TYPE(klass) == T_MODULE) {
            if (rb_obj_class(klass) == rb_cModule) {
                s = "Module";
            }
            else {
                s = rb_class2name(RBASIC(klass)->klass);
            }
        }
        len = 2 + strlen(s) + 3 + 2 * SIZEOF_LONG + 1;
        path = rb_str_new(0, len);
        snprintf(RSTRING(path)->ptr, len+1, "#<%s:0x%lx>", s, klass);
        RSTRING(path)->len = strlen(RSTRING(path)->ptr);
        rb_ivar_set(klass, tmp_classpath, path);

        return path;
    }
}

void
rb_set_class_path(klass, under, name)
    VALUE klass, under;
    const char *name;
{
    VALUE str;

    if (under == rb_cObject) {
        str = rb_str_new2(name);
    }
    else {
        str = rb_str_dup(rb_class_path(under));
        rb_str_cat2(str, "::");
        rb_str_cat2(str, name);
    }
    rb_ivar_set(klass, classpath, str);
}

VALUE
rb_path2class(path)
    const char *path;
{
    const char *pbeg, *p;
    ID id;
    VALUE c = rb_cObject;

    if (path[0] == '#') {
        rb_raise(rb_eArgError, "can't retrieve anonymous class %s", path);
    }
    pbeg = p = path;
    while (*p) {
        VALUE str;

        while (*p && *p != ':') p++;
        str = rb_str_new(pbeg, p-pbeg);
        id = rb_intern(RSTRING(str)->ptr);
        if (p[0] == ':') {
            if (p[1] != ':') goto undefined_class;
            p += 2;
            pbeg = p;
        }
        if (!rb_const_defined(c, id)) {
          undefined_class:
            rb_raise(rb_eArgError, "undefined class/module %.*s", p-path, path);
        }
        c = rb_const_get_at(c, id);
        switch (TYPE(c)) {
          case T_MODULE:
          case T_CLASS:
            break;
          default:
            rb_raise(rb_eTypeError, "%s does not refer class/module", path);
        }
    }

    return c;
}

void
rb_name_class(klass, id)
    VALUE klass;
    ID id;
{
    rb_iv_set(klass, "__classid__", ID2SYM(id));
}

VALUE
rb_class_name(klass)
    VALUE klass;
{
    return rb_class_path(rb_class_real(klass));
}

char *
rb_class2name(klass)
    VALUE klass;
{
    return RSTRING(rb_class_name(klass))->ptr;
}

char *
rb_obj_classname(obj)
    VALUE obj;
{
    return rb_class2name(CLASS_OF(obj));
}

struct trace_var {
    int removed;
    void (*func)();
    VALUE data;
    struct trace_var *next;
};

struct global_variable {
    int   counter;
    void *data;
    VALUE (*getter)();
    void  (*setter)();
    void  (*marker)();
    int block_trace;
    struct trace_var *trace;
};

struct global_entry {
    struct global_variable *var;
    ID id;
};

static VALUE undef_getter();
static void  undef_setter();
static void  undef_marker();

static VALUE val_getter();
static void  val_setter();
static void  val_marker();

static VALUE var_getter();
static void  var_setter();
static void  var_marker();

struct global_entry*
rb_global_entry(id)
    ID id;
{
    struct global_entry *entry;

    if (!st_lookup(rb_global_tbl, id, (st_data_t *)&entry)) {
        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);
    }
    return entry;
}

static VALUE
undef_getter(id)
    ID id;
{
    rb_warning("global variable `%s' not initialized", rb_id2name(id));

    return Qnil;
}

static void
undef_setter(val, id, data, var)
    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;
}

static void
undef_marker()
{
}

static VALUE
val_getter(id, val)
    ID id;
    VALUE val;
{
    return val;
}

static void
val_setter(val, id, data, var)
    VALUE val;
    ID id;
    void *data;
    struct global_variable *var;
{
    var->data = (void*)val;
}

static void
val_marker(data)
    VALUE data;
{
    if (data) rb_gc_mark_maybe(data);
}

static VALUE
var_getter(id, var)
    ID id;
    VALUE *var;
{
    if (!var) return Qnil;
    return *var;
}

static void
var_setter(val, id, var)
    VALUE val;
    ID id;
    VALUE *var;
{
    *var = val;
}

static void
var_marker(var)
    VALUE *var;
{
    if (var) rb_gc_mark_maybe(*var);
}

static void
readonly_setter(val, id, var)
    VALUE val;
    ID id;
    void *var;
{
    rb_name_error(id, "%s is a read-only variable", rb_id2name(id));
}

static int
mark_global_entry(key, entry)
    ID key;
    struct global_entry *entry;
{
    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()
{
    if (rb_global_tbl) {
        st_foreach(rb_global_tbl, mark_global_entry, 0);
    }
}

static ID
global_id(name)
    const char *name;
{
    ID id;

    if (name[0] == '$') id = rb_intern(name);
    else {
        char *buf = ALLOCA_N(char, strlen(name)+2);
        buf[0] = '$';
        strcpy(buf+1, name);
        id = rb_intern(buf);
    }
    return id;
}

void
rb_define_hooked_variable(name, var, getter, setter)
    const char  *name;
    VALUE *var;
    VALUE (*getter)();
    void  (*setter)();
{
    struct global_variable *gvar;
    ID id = global_id(name);

    gvar = rb_global_entry(id)->var;
    gvar->data = (void*)var;
    gvar->getter = getter?getter:var_getter;
    gvar->setter = setter?setter:var_setter;
    gvar->marker = var_marker;
}

void
rb_define_variable(name, var)
    const char  *name;
    VALUE *var;
{
    rb_define_hooked_variable(name, var, 0, 0);
}

void
rb_define_readonly_variable(name, var)
    const char  *name;
    VALUE *var;
{
    rb_define_hooked_variable(name, var, 0, readonly_setter);
}

void
rb_define_virtual_variable(name, getter, setter)
    const char  *name;
    VALUE (*getter)();
    void  (*setter)();
{
    if (!getter) getter = val_getter;
    if (!setter) setter = readonly_setter;
    rb_define_hooked_variable(name, 0, getter, setter);
}

static void
rb_trace_eval(cmd, val)
    VALUE cmd, 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(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE var, cmd;
    struct global_entry *entry;
    struct trace_var *trace;

    rb_secure(4);
    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(var)
    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;
            free(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(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE var, cmd;
    ID id;
    struct global_entry *entry;
    struct trace_var *trace;

    rb_scan_args(argc, argv, "11", &var, &cmd);
    id = rb_to_id(var);
    if (!st_lookup(rb_global_tbl, id, (st_data_t *)&entry)) {
        rb_name_error(id, "undefined global variable %s", rb_id2name(id));
    }

    trace = entry->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(entry)
    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(data)
    struct trace_data *data;
{
    struct trace_var *trace = data->trace;

    while (trace) {
        (*trace->func)(trace->data, data->val);
        trace = trace->next;
    }
    return Qnil;                /* not reached */
}

static VALUE
trace_en(var)
    struct global_variable *var;
{
    var->block_trace = 0;
    remove_trace(var);
    return Qnil;                /* not reached */
}

VALUE
rb_gvar_set(entry, val)
    struct global_entry *entry;
    VALUE val;
{
    struct trace_data trace;
    struct global_variable *var = entry->var;

    if (rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't change global variable value");
    (*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(name, val)
    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(name)
    const char *name;
{
    struct global_entry *entry;

    entry = rb_global_entry(global_id(name));
    return rb_gvar_get(entry);
}

VALUE
rb_gvar_defined(entry)
    struct global_entry *entry;
{
    if (entry->var->getter == undef_getter) return Qfalse;
    return Qtrue;
}

static int
gvar_i(key, entry, ary)
    ID key;
    struct global_entry *entry;
    VALUE ary;
{
    rb_ary_push(ary, rb_str_new2(rb_id2name(key)));
    return ST_CONTINUE;
}

/*
 *  call-seq:
 *     global_variables    => array
 *  
 *  Returns an array of the names of global variables.
 *     
 *     global_variables.grep /std/   #=> ["$stderr", "$stdout", "$stdin"]
 */

VALUE
rb_f_global_variables()
{
    VALUE ary = rb_ary_new();
    char buf[4];
    char *s = "&`'+123456789";

    st_foreach(rb_global_tbl, gvar_i, ary);
    if (!NIL_P(rb_backref_get())) {
        while (*s) {
            sprintf(buf, "$%c", *s++);
            rb_ary_push(ary, rb_str_new2(buf));
        }
    }
    return ary;
}

void
rb_alias_variable(name1, name2)
    ID name1;
    ID name2;
{
    struct global_entry *entry1, *entry2;

    if (rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't alias global variable");

    entry2 = rb_global_entry(name2);
    if (!st_lookup(rb_global_tbl, name1, (st_data_t *)&entry1)) {
        entry1 = ALLOC(struct global_entry);
        entry1->id = name1;
        st_add_direct(rb_global_tbl, name1, (st_data_t)entry1);
    }
    else if (entry1->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;
                free(trace);
                trace = next;
            }
            free(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(obj)
    VALUE obj;
{
    st_table *tbl;

    if (!FL_TEST(obj, FL_EXIVAR)) return 0;
    if (!generic_iv_tbl) return 0;
    if (!st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) return 0;
    return tbl;
}

static VALUE
generic_ivar_get(obj, id, warn)
    VALUE obj;
    ID id;
    int warn;
{
    st_table *tbl;
    VALUE val;

    if (generic_iv_tbl) {
      if (st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) {
        if (st_lookup(tbl, id, &val)) {
          return val;
        }
      }
    }
    if (warn) {
        rb_warning("instance variable %s not initialized", rb_id2name(id));
    }
    return Qnil;
}

static void
generic_ivar_set(obj, id, val)
    VALUE obj;
    ID id;
    VALUE val;
{
    st_table *tbl;

    if (rb_special_const_p(obj)) {
        special_generic_ivar = 1;
    }
    if (!generic_iv_tbl) {
        generic_iv_tbl = st_init_numtable();
    }

    if (!st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) {
        FL_SET(obj, FL_EXIVAR);
        tbl = st_init_numtable();
        st_add_direct(generic_iv_tbl, obj, (st_data_t)tbl);
        st_add_direct(tbl, id, val);
        return;
    }
    st_insert(tbl, id, val);
}

static VALUE
generic_ivar_defined(obj, id)
    VALUE obj;
    ID id;
{
    st_table *tbl;
    VALUE val;

    if (!generic_iv_tbl) return Qfalse;
    if (!st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) return Qfalse;
    if (st_lookup(tbl, id, &val)) {
        return Qtrue;
    }
    return Qfalse;
}

static int
generic_ivar_remove(obj, id, valp)
    VALUE obj;
    ID id;
    VALUE *valp;
{
    st_table *tbl;
    int status;

    if (!generic_iv_tbl) return 0;
    if (!st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) return 0;
    status = st_delete(tbl, &id, valp);
    if (tbl->num_entries == 0) {
        st_delete(generic_iv_tbl, &obj, (st_data_t *)&tbl);
        st_free_table(tbl);
    }
    return status;
}

void
rb_mark_generic_ivar(obj)
    VALUE obj;
{
    st_table *tbl;

    if (!generic_iv_tbl) return;
    if (st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) {
        rb_mark_tbl(tbl);
    }
}

static int
givar_mark_i(key, value)
    ID key;
    VALUE value;
{
    rb_gc_mark(value);
    return ST_CONTINUE;
}

static int
givar_i(obj, tbl)
    VALUE obj;
    st_table *tbl;
{
    if (rb_special_const_p(obj)) {
        st_foreach(tbl, givar_mark_i, 0);
    }
    return ST_CONTINUE;
}

void
rb_mark_generic_ivar_tbl()
{
    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(obj)
    VALUE obj;
{
    st_table *tbl;

    if (st_delete(generic_iv_tbl, &obj, (st_data_t *)&tbl))
        st_free_table(tbl);
}

void
rb_copy_generic_ivar(clone, obj)
    VALUE clone, obj;
{
    st_table *tbl;

    if (!generic_iv_tbl) return;
    if (st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) {
        st_table *old;

        if (st_lookup(generic_iv_tbl, clone, (st_data_t *)&old)) {
            st_free_table(old);
            st_insert(generic_iv_tbl, clone, (st_data_t)st_copy(tbl));
        }
        else {
            st_add_direct(generic_iv_tbl, clone, (st_data_t)st_copy(tbl));
        }
    }
}

static VALUE
ivar_get(obj, id, warn)
    VALUE obj;
    ID id;
    int warn;
{
    VALUE val;

    switch (TYPE(obj)) {
      case T_OBJECT:
      case T_CLASS:
      case T_MODULE:
        if (ROBJECT(obj)->iv_tbl && st_lookup(ROBJECT(obj)->iv_tbl, id, &val))
            return val;
        break;
      default:
        if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj))
            return generic_ivar_get(obj, id, warn);
        break;
    }
    if (warn) {
        rb_warning("instance variable %s not initialized", rb_id2name(id));
    }
    return Qnil;
}

VALUE
rb_ivar_get(obj, id)
    VALUE obj;
    ID id;
{
    return ivar_get(obj, id, Qtrue);
}

VALUE
rb_attr_get(obj, id)
    VALUE obj;
    ID id;
{
    return ivar_get(obj, id, Qfalse);
}

VALUE
rb_ivar_set(obj, id, val)
    VALUE obj;
    ID id;
    VALUE val;
{
    if (!OBJ_TAINTED(obj) && rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't modify instance variable");
    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
    switch (TYPE(obj)) {
      case T_OBJECT:
      case T_CLASS:
      case T_MODULE:
        if (!ROBJECT(obj)->iv_tbl) ROBJECT(obj)->iv_tbl = st_init_numtable();
        st_insert(ROBJECT(obj)->iv_tbl, id, val);
        break;
      default:
        generic_ivar_set(obj, id, val);
        break;
    }
    return val;
}

VALUE
rb_ivar_defined(obj, id)
    VALUE obj;
    ID id;
{
    switch (TYPE(obj)) {
      case T_OBJECT:
      case T_CLASS:
      case T_MODULE:
        if (ROBJECT(obj)->iv_tbl && st_lookup(ROBJECT(obj)->iv_tbl, id, 0))
            return Qtrue;
        break;
      default:
        if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj))
            return generic_ivar_defined(obj, id);
        break;
    }
    return Qfalse;
}

static int
ivar_i(key, entry, ary)
    ID key;
    struct global_entry *entry;
    VALUE ary;
{
    if (rb_is_instance_id(key)) {
        rb_ary_push(ary, rb_str_new2(rb_id2name(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(obj)
    VALUE obj;
{
    VALUE ary;

    ary = rb_ary_new();
    switch (TYPE(obj)) {
      case T_OBJECT:
      case T_CLASS:
      case T_MODULE:
        if (ROBJECT(obj)->iv_tbl) {
            st_foreach_safe(ROBJECT(obj)->iv_tbl, ivar_i, ary);
        }
        break;
      default:
        if (!generic_iv_tbl) break;
        if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj)) {
            st_table *tbl;

            if (st_lookup(generic_iv_tbl, obj, (st_data_t *)&tbl)) {
                st_foreach_safe(tbl, ivar_i, ary);
            }
        }
        break;
    }
    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(obj, name)
    VALUE obj, name;
{
    VALUE val = Qnil;
    ID id = rb_to_id(name);

    if (!OBJ_TAINTED(obj) && rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't modify instance variable");
    if (OBJ_FROZEN(obj)) rb_error_frozen("object");
    if (!rb_is_instance_id(id)) {
        rb_name_error(id, "`%s' is not allowed as an instance variable name", rb_id2name(id));
    }

    switch (TYPE(obj)) {
      case T_OBJECT:
      case T_CLASS:
      case T_MODULE:
        if (ROBJECT(obj)->iv_tbl && st_delete(ROBJECT(obj)->iv_tbl, (st_data_t*)&id, &val)) {
            return val;
        }
        break;
      default:
        if (FL_TEST(obj, FL_EXIVAR) || rb_special_const_p(obj)) {
            if (generic_ivar_remove(obj, id, &val)) {
                return val;
            }
        }
        break;
    }
    rb_name_error(id, "instance variable %s not defined", rb_id2name(id));
    return Qnil;                /* not reached */
}
static void uninitialized_constant (VALUE, ID);
static void
uninitialized_constant(klass, id)
    VALUE klass;
    ID id;
{
    if (klass && klass != rb_cObject)
        rb_name_error(id, "uninitialized constant %s::%s",
                      rb_class2name(klass),
                      rb_id2name(id));
    else {
        rb_name_error(id, "uninitialized constant %s", rb_id2name(id));
    }
}

static VALUE
const_missing(klass, id)
    VALUE klass;
    ID id;
{
    return rb_funcall(klass, rb_intern("const_missing"), 1, ID2SYM(id));
}


/*
 * 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 a (very bad) example: if 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
 *  value of the loaded class. It therefore implements a perverse
 *  kind of autoload facility.
 *  
 *    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(klass, name)
    VALUE klass, name;
{
    ruby_frame = ruby_frame->prev; /* pop frame for "const_missing" */
    uninitialized_constant(klass, rb_to_id(name));
    return Qnil;                /* not reached */
}

static struct st_table *
check_autoload_table(av)
    VALUE av;
{
    Check_Type(av, T_DATA);
    if (RDATA(av)->dmark != (RUBY_DATA_FUNC)rb_mark_tbl ||
        RDATA(av)->dfree != (RUBY_DATA_FUNC)st_free_table) {
        rb_raise(rb_eTypeError, "wrong autoload table: %s", RSTRING(rb_inspect(av))->ptr);
    }
    return (struct st_table *)DATA_PTR(av);
}

void
rb_autoload(mod, id, file)
    VALUE mod;
    ID id;
    const char *file;
{
    VALUE av, fn;
    struct st_table *tbl;

    if (!rb_is_const_id(id)) {
        rb_raise(rb_eNameError, "autoload must be constant name", rb_id2name(id));
    }
    if (!file || !*file) {
        rb_raise(rb_eArgError, "empty file name");
    }

    if ((tbl = RCLASS(mod)->iv_tbl) && st_lookup(tbl, id, &av) && av != Qundef)
        return;

    rb_const_set(mod, id, Qundef);
    tbl = RCLASS(mod)->iv_tbl;
    if (st_lookup(tbl, autoload, &av)) {
        tbl = check_autoload_table(av);
    }
    else {
        av = Data_Wrap_Struct(0 , rb_mark_tbl, st_free_table, 0);
        st_add_direct(tbl, autoload, av);
        DATA_PTR(av) = tbl = st_init_numtable();
    }
    fn = rb_str_new2(file);
    FL_UNSET(fn, FL_TAINT);
    OBJ_FREEZE(fn);
    st_insert(tbl, id, (st_data_t)rb_node_newnode(NODE_MEMO, fn, ruby_safe_level, 0));
}

static NODE*
autoload_delete(mod, id)
    VALUE mod;
    ID id;
{
    VALUE val;
    st_data_t load = 0;

    st_delete(RCLASS(mod)->iv_tbl, (st_data_t*)&id, 0);
    if (st_lookup(RCLASS(mod)->iv_tbl, autoload, &val)) {
        struct st_table *tbl = check_autoload_table(val);

        st_delete(tbl, (st_data_t*)&id, &load);

        if (tbl->num_entries == 0) {
            DATA_PTR(val) = 0;
            st_free_table(tbl);
            id = autoload;
            if (st_delete(RCLASS(mod)->iv_tbl, (st_data_t*)&id, &val)) {
                rb_gc_force_recycle(val);
            }
        }
    }

    return (NODE *)load;
}

VALUE
rb_autoload_load(klass, id)
    VALUE klass;
    ID id;
{
    VALUE file;
    NODE *load = autoload_delete(klass, id);

    if (!load || !(file = load->nd_lit) || rb_provided(RSTRING(file)->ptr)) {
        return Qfalse;
    }
    return rb_require_safe(file, load->nd_nth);
}

static VALUE
autoload_file(mod, id)
    VALUE mod;
    ID id;
{
    VALUE val, file;
    struct st_table *tbl;
    st_data_t load;

    if (!st_lookup(RCLASS(mod)->iv_tbl, autoload, &val) ||
        !(tbl = check_autoload_table(val)) || !st_lookup(tbl, id, &load)) {
        return Qnil;
    }
    file = ((NODE *)load)->nd_lit;
    Check_Type(file, T_STRING);
    if (!RSTRING(file)->ptr || !*RSTRING(file)->ptr) {
        rb_raise(rb_eArgError, "empty file name");
    }
    if (!rb_provided(RSTRING(file)->ptr)) {
        return file;
    }

    /* already loaded but not defined */
    st_delete(tbl, (st_data_t*)&id, 0);
    if (!tbl->num_entries) {
        DATA_PTR(val) = 0;
        st_free_table(tbl);
        id = autoload;
        if (st_delete(RCLASS(mod)->iv_tbl, (st_data_t*)&id, &val)) {
            rb_gc_force_recycle(val);
        }
    }
    return Qnil;
}

VALUE
rb_autoload_p(mod, id)
    VALUE mod;
    ID id;
{
    struct st_table *tbl = RCLASS(mod)->iv_tbl;
    VALUE val;

    if (!tbl || !st_lookup(tbl, id, &val) || val != Qundef) {
        return Qnil;
    }
    return autoload_file(mod, id);
}

static VALUE
rb_const_get_0(klass, id, exclude, recurse)
    VALUE klass;
    ID id;
    int exclude, recurse;
{
    VALUE value, tmp;
    int mod_retry = 0;

    tmp = klass;
  retry:
    while (tmp) {
        while (RCLASS(tmp)->iv_tbl && st_lookup(RCLASS(tmp)->iv_tbl,id,&value)) {
            if (value == Qundef) {
                if (!RTEST(rb_autoload_load(tmp, id))) break;
                continue;
            }
            if (exclude && tmp == rb_cObject && klass != rb_cObject) {
                rb_warn("toplevel constant %s referenced by %s::%s",
                        rb_id2name(id), rb_class2name(klass), rb_id2name(id));
            }
            return value;
        }
        if (!recurse && klass != rb_cObject) break;
        tmp = RCLASS(tmp)->super;
    }
    if (!exclude && !mod_retry && BUILTIN_TYPE(klass) == T_MODULE) {
        mod_retry = 1;
        tmp = rb_cObject;
        goto retry;
    }

    return const_missing(klass, id);
}

VALUE
rb_const_get_from(klass, id)
    VALUE klass;
    ID id;
{
    return rb_const_get_0(klass, id, Qtrue, Qtrue);
}

VALUE
rb_const_get(klass, id)
    VALUE klass;
    ID id;
{
    return rb_const_get_0(klass, id, Qfalse, Qtrue);
}

VALUE
rb_const_get_at(klass, id)
    VALUE klass;
    ID id;
{
    return rb_const_get_0(klass, id, Qtrue, Qfalse);
}

/*
 *  call-seq:
 *     remove_const(sym)   => obj
 *  
 *  Removes the definition of the given constant, returning that
 *  constant's value. Predefined classes and singleton objects (such as
 *  <i>true</i>) cannot be removed.
 */

VALUE
rb_mod_remove_const(mod, name)
    VALUE mod, name;
{
    ID id = rb_to_id(name);
    VALUE val;

    if (!rb_is_const_id(id)) {
        rb_name_error(id, "`%s' is not allowed as a constant name", rb_id2name(id));
    }
    if (!OBJ_TAINTED(mod) && rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't remove constant");
    if (OBJ_FROZEN(mod)) rb_error_frozen("class/module");

    if (RCLASS(mod)->iv_tbl && st_delete(ROBJECT(mod)->iv_tbl, (st_data_t*)&id, &val)) {
        if (val == Qundef) {
            autoload_delete(mod, id);
            val = Qnil;
        }
        return val;
    }
    if (rb_const_defined_at(mod, id)) {
        rb_name_error(id, "cannot remove %s::%s",
                 rb_class2name(mod), rb_id2name(id));
    }
    rb_name_error(id, "constant %s::%s not defined",
                  rb_class2name(mod), rb_id2name(id));
    return Qnil;                /* not reached */
}

static int
sv_i(key, value, tbl)
    ID key;
    VALUE value;
    st_table *tbl;
{
    if (rb_is_const_id(key)) {
        if (!st_lookup(tbl, key, 0)) {
            st_insert(tbl, key, key);
        }
    }
    return ST_CONTINUE;
}

void*
rb_mod_const_at(mod, data)
    VALUE mod;
    void *data;
{
    st_table *tbl = data;
    if (!tbl) {
        tbl = st_init_numtable();
    }
    if (RCLASS(mod)->iv_tbl) {
        st_foreach_safe(RCLASS(mod)->iv_tbl, sv_i, (st_data_t)tbl);
    }
    return tbl;
}

void*
rb_mod_const_of(mod, data)
    VALUE mod;
    void *data;
{
    VALUE tmp = mod;
    for (;;) {
        data = rb_mod_const_at(tmp, data);
        tmp = RCLASS(tmp)->super;
        if (!tmp) break;
        if (tmp == rb_cObject && mod != rb_cObject) break;
    }
    return data;
}

static int
list_i(key, value, ary)
    ID key, value;
    VALUE ary;
{
    rb_ary_push(ary, rb_str_new2(rb_id2name(key)));
    return ST_CONTINUE;
}

VALUE
rb_const_list(data)
    void *data;
{
    st_table *tbl = data;
    VALUE ary;

    if (!tbl) return rb_ary_new2(0);
    ary = rb_ary_new2(tbl->num_entries);
    st_foreach(tbl, list_i, ary);
    st_free_table(tbl);

    return ary;
}

/*
 *  call-seq:
 *     mod.constants    => 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).
 */

VALUE
rb_mod_constants(mod)
    VALUE mod;
{
    return rb_const_list(rb_mod_const_of(mod, 0));
}