Bug 4114 - MonoTouch attempts to JIT certain code patterns at runtime
Summary: MonoTouch attempts to JIT certain code patterns at runtime
Alias: None
Product: iOS
Classification: Xamarin
Component: General ()
Version: 5.2
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2012-03-27 16:43 UTC by David Merriman
Modified: 2013-05-29 20:20 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

Project containing three situations where MonoTouch attempts to JIT at runtime (4.75 MB, application/zip)
2012-03-27 16:43 UTC, David Merriman

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Description David Merriman 2012-03-27 16:43:58 UTC
Created attachment 1583 [details]
Project containing three situations where MonoTouch attempts to JIT at runtime

Attached is a project which demonstrates 3 different situations we've run into where cross-platform code is not AOT compiled, and crashes at runtime.  They can be observed by defining the symbols JIT_FAIL_1, JIT_FAIL_2, and JIT_FAIL_3 respectively.  All still try to JIT at runtime as of MonoTouch 5.2.10.  I have not yet tried any of the alphas.

The first situation is an override of a virtual generic method.  I believe this is expected to fail, since it is probably impossible to compile such a method AOT.  However, for projects that share code with environments that allow JIT compilation, it would be nice if MonoTouch could detect this particular pattern at compile time and fail the build.

The other two situations involve generic types, IEnumerable, and extension methods, and it's possible that they could be detected and compiled correctly AOT, but right now that is not happening.  If possible, they should be compiled AOT.  If not, it would be preferable to have a compile time error instead of finding it at run time - especially because these two situations are harder to detect with the static analysis tools we're using to mitigate the issue right now.

Also, here is the StackOverflow question that prompted this bug report, for completeness:
Comment 1 Sebastien Pouliot 2012-03-28 16:27:24 UTC
I can confirm the three cases still fails with the latest alpha release.

The first one for being a generic virtual method.

The other two looks related to the use of KeyValuePair<TKey,TValue> which is a value-type and often, like the test case, nested a few times. That makes them harder to detect (or workaround).

I'll include the tests in our test suite (so we can test new ideas and version against it) and we'll update this bug report whenever one is fixed. Thanks.
Comment 2 Sebastien Pouliot 2013-05-29 20:20:12 UTC
The three test cases we added for this bug now works fine in 6.3.x.

6.3.x beta releases have much improved to avoid this situation (the EngineExecutionException). You might want to try this, or similar code, again and report any remaining issues (with a test case).