Memory leaks in Alsa backend

[druskus20]

I am finding quite a lot of memory leaks when using Alsa, both on master and 0.15.3.

==1297036== 1,512 bytes in 21 blocks are possibly lost in loss record 142 of 164
==1297036==    at 0x484D953: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==1297036==    by 0x48B3D92: ??? (in /usr/lib/x86_64-linux-gnu/libasound.so.2.0.0)
==1297036==    by 0x48C4C44: ??? (in /usr/lib/x86_64-linux-gnu/libasound.so.2.0.0)
==1297036==    by 0x48C5289: ??? (in /usr/lib/x86_64-linux-gnu/libasound.so.2.0.0)
==1297036==    by 0x48CFD84: snd_config_update_r (in /usr/lib/x86_64-linux-gnu/libasound.so.2.0.0)
==1297036==    by 0x48D0447: snd_config_update_ref (in /usr/lib/x86_64-linux-gnu/libasound.so.2.0.0)
==1297036==    by 0x48FB35F: snd_pcm_open (in /usr/lib/x86_64-linux-gnu/libasound.so.2.0.0)
==1297036==    by 0x4E95A4: alsa::pcm::PCM::open (error.rs:21)
==1297036==    by 0x4E94A0: alsa::pcm::PCM::new (pcm.rs:147)
==1297036==    by 0x4D9F04: cpal::host::alsa::DeviceHandles::try_open (mod.rs:214)
==1297036==    by 0x4DA099: cpal::host::alsa::DeviceHandles::take (mod.rs:233)
==1297036==    by 0x4DA372: cpal::host::alsa::Device::build_stream_inner (mod.rs:251)
==1297036==

This can be seen in some of the examples, for example feedback.

 valgrind -s --leak-check=full --show-leak-kinds=all ./target/debug/examples/feedback

Seems to be the same as this:

jarikomppa/soloud#278

[druskus20]

Looking a bit further into this I realized it is an issue with alsa-rs itself. I opened an issue there.

[druskus20]

Issue is fixed in alsa-rs - a simple upgrade whenever a new alsa_rs version is released will fix this issue

[bluenote10]

Thanks for looking into this, and the update on it!

Doesn't the fix in diwic/alsa-rs@e560e9d suggest that update_free_global now needs to be called pro-actively by cpal?

[druskus20]

Oh yeah, fair - sorry completely my bad (my PR is the one that fixed it automatically 😅)

We should either assume a reasonable default or allow the user to free the global config on demand