/*
 *   call-seq:
 *      context.stop_frame(frame)
 *
 *   Stops when a frame with number +frame+ is activated. Implements +up+ and +down+ commands.
 */
static VALUE
context_stop_frame(VALUE self, VALUE frame)
{
    debug_context_t *debug_context;

    debug_check_started();
    Data_Get_Struct(self, debug_context_t, debug_context);
    if(FIX2INT(frame) < 0 && FIX2INT(frame) >= debug_context->stack_size)
        rb_raise(rb_eRuntimeError, "Stop frame is out of range.");
    debug_context->stop_frame = debug_context->stack_size - FIX2INT(frame);

    return frame;
}