ubsan: `runtime error: variable length array bound evaluates to non-positive value 0`

ubsan: `runtime error: variable length array bound evaluates to non-positive value 0`

[GitHub issues - opened]

alsa-project/alsa-lib issue #505 was opened from pobrn:

While testing pipewire with a sanitized build of alsa-lib, the following is reported:

<details>

```
/pipewire/subprojects/alsa/src/pcm/pcm.c:7827:4: runtime error: variable length array bound evaluates to non-positive value 0
    #0 0x7b5f909a1e7d in snd_pcm_slave_conf (/pipewire/build/subprojects/alsa/dist/usr/lib/libasound.so.2+0x5a1e7d) (BuildId: 2137baa0902bc081fc7d45192f387a7550800d43)
    #1 0x7b5f90a9e29c in _snd_pcm_empty_open (/pipewire/build/subprojects/alsa/dist/usr/lib/libasound.so.2+0x69e29c) (BuildId: 2137baa0902bc081fc7d45192f387a7550800d43)
    #2 0x7b5f9098bd9a in snd_pcm_open_conf (/pipewire/build/subprojects/alsa/dist/usr/lib/libasound.so.2+0x58bd9a) (BuildId: 2137baa0902bc081fc7d45192f387a7550800d43)
    #3 0x7b5f9098c78e in snd_pcm_open_noupdate (/pipewire/build/subprojects/alsa/dist/usr/lib/libasound.so.2+0x58c78e) (BuildId: 2137baa0902bc081fc7d45192f387a7550800d43)
    #4 0x7b5f9098c9d4 in snd_pcm_open (/pipewire/build/subprojects/alsa/dist/usr/lib/libasound.so.2+0x58c9d4) (BuildId: 2137baa0902bc081fc7d45192f387a7550800d43)
    #5 0x7b5f91ccdf07 in pa_alsa_open_by_device_string ../spa/plugins/alsa/acp/alsa-util.c:716
[...]
```

</details>

While this is probably generally harmless in practice, if there is a simple change to avoid it, it would be nice to have it fixed.

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/505
Repository URL: https://github.com/alsa-project/alsa-lib