Bug 208929 – WebAssembly stack overflow limit on iPad is much lower than desktop

• Status: NEW
• Component: WebAssembly

I work at Figma (https://www.figma.com) and I'm looking into getting Figma to run in Safari on an iPad. One problem is that none of our Figma plugins work on the iPad.

Figma plugins are 3rd-party JavaScript code that our users can write to augment Figma. We're using a C JavaScript VM (https://bellard.org/quickjs/) compiled to WebAssembly to sandbox our plugins for security (we tried other approaches but they didn't work, read https://www.figma.com/blog/an-update-on-plugin-security/ for more info). However, running any Figma plugin results in "Maximum call stack size exceeded". This is not a problem in Safari on desktop.

The issue appears to be a stack overflow in the QuickJS JavaScript parser, which is written using recursion and must do one level of recursion for every JavaScript operator precedence level. It looks like the WebAssembly stack overflow limit in Safari on iPad is much lower than desktop (maybe around 100 entries?), so the parser overflows the stack even when parsing pretty trivial JavaScript code.

Is it possible to fix this, or do you know of a workaround that we could use? Figma plugins are an important part of the user experience. Our users are professional designers and often rely on plugins to get their work done.

Repro steps:

1. Sign up for a Figma account on https://www.figma.com (it's free)
2. Click on "Plugins" in the top left
3. Click on a plugin to install it (e.g. "Kaleidocode" from Microsoft: https://www.figma.com/community/plugin/736060893363678891/Kaleidocode)
4. Log in to Figma in Safari on iPad
5. Create a new document by clicking the "+" button
6. Open the hamburger menu in the top left and select "Plugins > Kaleidocode"

Expected: The plugin should run fine like it does on desktop.
Unexpected: We get the error "Maximum call stack size exceeded" from Safari.

[Radar WebKit Bug Importer]

<rdar://problem/60348868>

[Keith Miller]

I think this has been reported before. Have you tried running this on the latest beta? I believe this issue should be fixed.

As for a work around, I don't know if there is one for older Safari, sadly. Other than restructuring your code but that's probably not ideal.