JIT exception thrown when creating animated gif on iOS #762

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1. JimBobSquarePants commented on Oct 30, 2018

   

   JimBobSquarePants

   on Oct 30, 2018

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   @dmanning23 Thanks for the info and initial research

   https://developer.xamarin.com/guides/ios/advanced_topics/limitations/

   I have no experience with mobile development so hopefully someone reads this and has a clue what this actually means.
2. dmanning23 commented on Oct 30, 2018

   

   dmanning23

   on Oct 30, 2018

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   The guidelines mention an attribute that can be used to decorate the problem method. There are a few examples out there showing how to use it, I was going to fart around with it later this afternoon and see if I can get it working.
3. JimBobSquarePants

   added

   help needed

   on Oct 30, 2018
4. antonfirsov commented on Oct 30, 2018

   

   antonfirsov

   on Oct 30, 2018

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   It seems to me that you are facing this specific limiatation.

   @dmanning23 can you try a little experiment for us?

   1. Create an application referencing the dev/MyGet version of ImageSharp and System.Memory, that does nothing else but
   2. PixelOperations<Bgra32> operations = PixelOperations<Bgra32>.Instance
   3. Invoke something like this method on the instance created in (2.), using reflection.
      Notes:
      • reflection is needed because the method is internal
      • to get an instance to Span<T> you can use the extension method array.AsSpan()
      • Span<T> is implictily convertible to ReadOnlySpan<T>)

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5. antonfirsov commented on Oct 30, 2018

   

   antonfirsov

   on Oct 30, 2018

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   @dmanning23 as @JimBobSquarePants mentioned, there are no Xamarin devs in the core team, but I have a few more ideas to try, if it's possible for you to use a manually built version of ImageSharp.

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6. dmanning23 commented on Nov 2, 2018

   

   dmanning23

   on Nov 2, 2018

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   Ok, I've made a bit of headway on this issue... If I explicitly build one of those objects (with the correct generic type) and call the ConstructPalette method BEFORE calling SaveAsGif(...):

   var test = new OctreeFrameQuantizer<Rgba32>(new OctreeQuantizer(false));
   test.AotGetPalette(); //stubbed out method that just calls empty ConstructPalette
   

   Now when it hits that bit of code when calling SaveAsGif<Rgba32>, it has already seen it ahead-of-time and doesn't need to spin up the JIT compiler. I can't think of a very elegant way to fix it though... The easiest thing I can think of is adding a few AotCompile methods that are similar to above, that the user can call at init on iOS.
   kinda gross, but it would work :) I'll put together a PR so yall can give me your thoughts.

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7. dlemstra commented on Nov 5, 2018

   

   dlemstra

   on Nov 5, 2018

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   Have you tried any of the workarounds mentioned here: https://support.frozenmountain.com/hc/en-us/articles/115000767214-Known-Issue-with-Xamarin-iOS-10-10.
8. dmanning23 commented on Nov 5, 2018

   

   dmanning23

   on Nov 5, 2018

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   Looks like those workarounds are if this issue pops up from calling p/invoke, I don't think any of those would work because the error here is due to the heavy generic usage in ImageSharp. I have a PR open that adds a few methods that can be used to pre-seed the AoT compiler on iOS. I've been able to generate animated gifs on iOS using this technique :)

   👍React with 👍2Reacted by Anton Firszov and James Jackson-South
9. dmanning23

   closed this as completedon Nov 12, 2018