Crash in `makeCubic` if cc.deltaT is INF / NAN

[mattreaganmozilla]

I'm investigating crash reports from our iOS users and although I haven't been able to reproduce the crashes directly, from the stacktraces it appears that they're occurring in SwiftDraw.makeCubic() in this calculation:

let segments = max(Int(ceil(abs(cc.deltaT) / (LayerTree.Float.tau / 4.0))), 1)

I confirmed that if cc.deltaT is INF or NAN a fatal error will occur.

Can anyone possibly provide further insight into this, or have any ideas as to the type of SVG (perhaps malformed) that could cause this issue?

Note: we're using SwiftDraw 0.17.0, though it doesn't appear at a glance that the recent releases would have addressed this particular issue. But please LMK if they may have addressed this.

Thank you

[swhitty]

Thank you for reporting it — there have not been any recent changes to the arc to cubic conversion.

Do you happen to have a a sample arc segment command e.g A 50 50 0 1 0 50 50 that may trigger the INF?

I've had a Quick Look and there may be a long standing issue within func vectorAngle()

A quick search of other libraries reveals slightly different calculations;

• svg-arc-to-cubic-bezier (node)
• SVGPath (Swift)

[swhitty]

A defensive fix to prevent propagation of NaN has been included in today's 0.18.3 release.

[mattreaganmozilla]

Thank you for reporting it — there have not been any recent changes to the arc to cubic conversion.

Thanks so much @swhitty for the quick response.

Do you happen to have a a sample arc segment command e.g A 50 50 0 1 0 50 50 that may trigger the INF?

Unfortunately I haven't yet identified the SVG that appears to have caused this for the user(s). I'm attempting to get a few more details, if I'm able to find an example I will be sure to update. Thank you again for the fast turnaround

[swhitty]

I have managed to create a path that triggers the trap in earlier SwiftDraw version;

<path d="M 1e-12,50 A1,1e-16 0 0 0 1e-7,50" fill="none" />

These values lead to a calculation of INF × 0.0 which results in NaN.

The good news is that the 0.18.3 release resolves the issue.

A sample SVG with the above path is attached and has been deployed to https://www.whileloop.com/images/favicon.svg

[swhitty]

Looks like this is now fixed