remove_class_variable

/*
 *  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)
 *       puts(defined? @@var)
 *     end
 *     
 *  <em>produces:</em>
 *     
 *     99
 *     nil
 */

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

    if (!rb_is_class_id(id)) {
	rb_name_error(id, "wrong class variable name %s", rb_id2name(id));
    }
    if (!OBJ_TAINTED(mod) && rb_safe_level() >= 4)
	rb_raise(rb_eSecurityError, "Insecure: can't remove class variable");
    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)) {
	return val;
    }
    if (rb_cvar_defined(mod, id)) {
	rb_name_error(id, "cannot remove %s for %s",
		 rb_id2name(id), rb_class2name(mod));
    }
    rb_name_error(id, "class variable %s not defined for %s",
		  rb_id2name(id), rb_class2name(mod));
    return Qnil;		/* not reached */
}