Try again to fix Coverity warning in SDL Sound

[weirddan455]

Description

The previous PR did not solve the issue. Coverity saw my assert and still thinks it's freeing from the middle of the list.

It's possible it is seeing a data race. I've removed the use of the volatile keyword and used a mutex lock around the entire loop. Sound_FreeSample also takes a lock but SDL's mutex is recursive so this should be fine.

This also removes a temporary variable that was maybe confusing Coverity. Now Sound_FreeSample is explicitly being called with sample_list (head of the linked list).

Related issues

#2996

Manual testing

Started Quake with ripped .ogg sound files. Closed Dosbox and confirmed there was no crashes or deadlocks.

Checklist

Please tick the items as you have addressed them. Don't remove items; leave the ones that are not applicable unchecked.

I have:

• followed the project's contributing guidelines and code of conduct.
• performed a self-review of my code.
• commented on the particularly hard-to-understand areas of my code.
• split my work into well-defined, bisectable commits, and I named my commits well.
• applied the appropriate labels (bug, enhancement, refactoring, documentation, etc.)
• checked that all my commits can be built.
• confirmed that my code does not cause performance regressions (e.g., by running the Quake benchmark).
• added unit tests where applicable to prove the correctness of my code and to avoid future regressions.
• made corresponding changes to the documentation or the website according to the documentation guidelines.
• locally verified my website or documentation changes.

[weirddan455]

I'm not sure what's wrong with the macOS build. I've seen it fail like this before randomly. I think this is the machine you run locally @kcgen ?

Can't find 'action.yml', 'action.yaml' or 'Dockerfile' under '/Volumes/RamDrive/ccache/tmp/_actions/actions/checkout/v4'. Did you forget to run actions/checkout before running your local action?

[kcgen]

Looks good, @weirddan455.
Let's see what Coverity thinks.

[kcgen]

I'm not sure what's wrong with the macOS build. I've seen it fail like this before randomly. I think this is the machine you run locally @kcgen ?

Can't find 'action.yml', 'action.yaml' or 'Dockerfile' under '/Volumes/RamDrive/ccache/tmp/_actions/actions/checkout/v4'. Did you forget to run actions/checkout before running your local action?

Yes - this has eluded me. The machine runs a single GitHub's "runner" process; it's in charge of managing its workspace where it checks out the project and run the CI commands.

The runs happen serially, usually with a couple seconds between back-to-back runs.

When it goes off the rails, Meson reports that a bunch of critical project files are missing - like in this case, docs/dosbox.1, which should be impossible because the runner checks out the project (and the branch), sets up dependencies, etc.. before setting up the build.

My only hunch is that there's some kind of race-condition where the runner purges the content from a running job, and it impacts the current job, because the runner does re-use the same directory tree for subsequent jobs.

I've stopped the runner, purged all the directories, and restarted it - for what it's worth (probably nothing 🤦 ).

There isn't much to configure with the runners - you tie them into a project, point the runner service to its workspace area, and just let it run.