previous_frame    964 eval.c             rb_control_frame_t *prev_cfp = previous_frame(GET_THREAD());
previous_frame    972 eval.c             rb_control_frame_t *prev_cfp = previous_frame(GET_THREAD());
previous_frame   1299 eval.c             rb_control_frame_t *prev_cfp = previous_frame(GET_THREAD());
previous_frame   1439 eval.c             rb_control_frame_t *prev_cfp = previous_frame(GET_THREAD());