class_variable_set

/*
 *  call-seq:
 *     obj.class_variable_set(symbol, obj)    => obj
 *  
 *  Sets the class variable names by <i>symbol</i> to
 *  <i>object</i>.
 *     
 *     class Fred
 *       @@foo = 99
 *       def foo
 *         @@foo
 *       end
 *     end
 *
 *     def Fred.foo
 *       class_variable_set(:@@foo, 101)      #=> 101
 *     end
 *     Fred.foo
 *     Fred.new.foo                             #=> 101
 */

static VALUE
rb_mod_cvar_set(obj, iv, val)
    VALUE obj, iv, val;
{
    ID id = rb_to_id(iv);

    if (!rb_is_class_id(id)) {
        rb_name_error(id, "`%s' is not allowed as a class variable name", rb_id2name(id));
    }
    rb_cvar_set(obj, id, val, Qfalse);
    return val;
}