[alsa-devel] PCM -- no need to release params mem nor close handle?

I am looking at PCM interface manual http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html

It tells that there are an open and set_params functions but nothing about close(). Furthermore, the description of open() http://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m.html#g8340c7dc0a... neither tells that. Ok, I have realized from the examples. However, even the examples demonstrate no params deallocation. You call the snd_pcm_hw_params_alloca(&hwparams) but never release the allocated memory. Why?

Thank you.