alsa-project/alsa-lib issue #493 was edited from Hoosier-Beagler:
The little gem shown below has broken a lot of code. Previously, no positive results were returned and software relied on -EAGAIN to detect remaining data. That result is no longer returned if some data was processed. This has broken the old and stable version of my application written in C(++) which is no longer being maintained. I have ported my app to python but this change has also broken public python wrappers for the alsa library. In [alsa-python / pyalsa / alsaseq.c](https://github.com/alsa-project/alsa-python/blob/master/pyalsa/alsaseq.c) below line 2800 and also [python-alsa-midi / alsa_midi / client.py](https://github.com/Jajcus/python-alsa-midi/blob/main/alsa_midi/client.py) at line 626 and possibly the sub-classes as well (lines 1679, 1871). None of these wrappers expected a valid return value and do not pass along said value returned from the c library call. Consequently, there is no longer an indication that the output has not been fully drained.
``` --- alsa-lib-1.2.14/src/seq/seq.c 2025-04-14 11:42:04.000000000 -0500 +++ alsa-lib-1.2.15.2/src/seq/seq.c 2026-01-08 08:27:57.000000000 -0600 @@ -4445,21 +4445,22 @@ int snd_seq_drain_output(snd_seq_t *seq) { ssize_t result, processed = 0; assert(seq); while (seq->obufused > 0) { result = seq->ops->write(seq, seq->obuf, seq->obufused); if (result < 0) { - if (result == -EAGAIN && processed) + if (result == -EAGAIN && processed > 0) return seq->obufused; return result; } if ((size_t)result < seq->obufused) memmove(seq->obuf, seq->obuf + result, seq->obufused - result); seq->obufused -= result; + processed += result; } return 0; }
/** * \brief extract the first event in output buffer * \param seq sequencer handle
```
Issue URL : https://github.com/alsa-project/alsa-lib/issues/493 Repository URL: https://github.com/alsa-project/alsa-lib