Fix a few memory issues found with ASan

[messmerd]

I used an AddressSanitizer build to find and fix some memory issues:

• Memory leak in LADSPA effects
• Memory leak in SimpleTextFloat
• Invalid iterator in AutomationClip
  • Occurred when adding and removing nodes in the Automation Editor
  • Likely the cause of Automation Editor crashes that I've experienced before
• Buffer overflow in PianoView
  • I didn't understand the logic of the code I wanted to fix, so I rewrote it. It works in a more straightforward and understandable way now, and the buffer overflow problem is fixed.
  • Fixes LMMS crashes when going left down piano in any instrument. #6608

I'm sure there are more memory-related errors I could find and fix with ASan, but this is enough for now.

[DomClark]

Do you plan on contributing the CAPS changes upstream? I checked https://github.com/moddevices/caps-lv2 and it appears the destructor still isn't virtual there.

[messmerd]

@DomClark
I just submitted a PR for the CAPS changes upstream: mod-audio/caps-lv2#32

I guess next I should revert those changes in this PR and then later update the CAPS submodule if/when it gets merged upstream?

[DomClark]

I guess next I should revert those changes in this PR and then later update the CAPS submodule if/when it gets merged upstream?

I think it's fine to keep the changes here. It doesn't looks like we've updated CAPS in a long time, and doing so is probably a somewhat larger task that shouldn't be a prerequisite for this fix. We've made a number of changes to our vendored copy of CAPS anyway, so it's not as if there isn't precedent for fixing things here.

[tresf]

I guess next I should revert those changes in this PR and then later update the CAPS submodule if/when it gets merged upstream?

I think it's fine to keep the changes here. It doesn't looks like we've updated CAPS in a long time, and doing so is probably a somewhat larger task that shouldn't be a prerequisite for this fix. We've made a number of changes to our vendored copy of CAPS anyway, so it's not as if there isn't precedent for fixing things here.

We have an open PR with the upstream fork here: #4027. I think it's worthwhile to send any patches there. Technically, they should probably go to Tim Goetze. I'm not sure how often moddevices sends their code to him. He's pretty picky about patches, quoting:

Contact
If you think you have found a bug in CAPS, or if you want to make a related or unrelated remark or inquiry please write to tim@quitte.de. 

Patches
Please do not send patches without asking first.  By submitting a patch, you claim sole authorship and agree that your submission becomes mine to use in any way I see fit, in exchange for no obligation on my part except attribution in the CAPS documentation. 

If we decide not to, that's OK too... the patches will just get lost once we upgrade and we'll have to backtrack a little.

[messmerd]

@tresf I contacted Tim Goetze in early September and we agreed upon a solution to the memory leak, but he hasn't released a new version of CAPS yet. I don't know when/if he plans to.