NaN formula values crash Surge XT when a note is played

[xard-dev]

Bug Description:
NaN formula values crash Surge XT when a note is played.

Surge Version
Surge XT 0.99.main.007a427

• Version:
• Plugin Type: LV2
• Bitness: 64-bit

Reproduction Steps:
Steps to reproduce the behavior:

1. Open first example preset "01 A Simple Formula".
2. Click on "FORM 1.1".
3. Click on the "Pen icon" to open Formula editor.
4. Change row "pclamp = limit_range(modstate["intphase"], 0, 10) / 10" tail to "... / 0".
5. Play a note.

Expected Behavior:
No sound is played and additionally an error message is displayed in some method.

Screenshots:

Computer Information (please complete the following information):

• OS: Ubuntu 20.04 LTS
• Host: Carla / Standalone
• Version: 2.1.0

[baconpaul]

Great reports this morning! Thanks so much!!

[mkruselj]

Just FYI no need to put XT in the title since we're not going back to fixing 1.9 so everything that is reported already basically pertains to XT. Thanks!

[xard-dev]

Alright, I'll drop the prefix then.

[baconpaul]

on my mac this doesn't crash but does of course produce garbage
i wonder if you have fpe on in your host
but i can put a std::is_finite() check when i pull the values from lua back into c++ world

[baconpaul]

but first let me fire up linux and see if it crashes there.

[xard-dev]

Confirmed that the crash happens on standalone as well.

[baconpaul]

Right so there's a few things happening here

First of all the juce path renderer on linux throws exceptions with nans. Fine.

But more importantly, our limit_range assumes a finite input so with a nan all our checks blow up. The particular stack in this case happens in SurgeVoice where we use the pitch to interpolate across a 2^x interpolation array in the filter blah blah and it would be fine if we were accidentally out of bounds as long as we are finite

I don't want to make limit_range check std::isfinite. We use that everywhere. So the fix I propose - since we have made sure all the rest of the modulators never make nan and we can't guarantee that with lua - is to just check isfinite on the outbound of the formula modulator, set a flag, and voila.

Will do that now.