[wasm][aot][tests] System.Runtime.CompilerServices.Unsafe.Tests failures

[radical]

This can be reproduced on main.

Logs

[19:47:49] fail: [FAIL] System.Runtime.CompilerServices.UnsafeTests.NullRef
[19:47:49] info: Assert.Throws() Failure
[19:47:49] info: Expected: typeof(System.NullReferenceException)
[19:47:49] info: Actual:   (No exception was thrown)
[19:47:49] info: 
[19:47:52] info: Finished:    System.Runtime.CompilerServices.Unsafe.Tests.dll

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Issue Details

---

Logs

[19:47:49] fail: [FAIL] System.Runtime.CompilerServices.UnsafeTests.NullRef
[19:47:49] info: Assert.Throws() Failure
[19:47:49] info: Expected: typeof(System.NullReferenceException)
[19:47:49] info: Actual:   (No exception was thrown)
[19:47:49] info: 
[19:47:52] info: Finished:    System.Runtime.CompilerServices.Unsafe.Tests.dll

Author:	radical
Assignees:	-
Labels:	arch-wasm, area-Codegen-AOT-mono, wasm-aot-test
Milestone:	-

[vargaz]

This is not a wasm bug, in release mode, for the following code:

        Action a = () => Unsafe.NullRef<int>();

roslyn generates (in release mode):

      IL_0000:  call       !!0& [System.Runtime.CompilerServices.Unsafe]System.Runtime.CompilerServices.Unsafe::NullRef<int32>()
      IL_0005:  pop

So there is nothing to throw a nullref anymore.

[radical]

With /p:EnableAggressiveTrimming=true, this passes, but with /p:EnableAggressiveTrimming=true /p:RunAOTCompilation=true, it fails. Why does it pass in the first case?

[radical]

I think:

• the exception is getting thrown
• but it gets eaten up somehow?
• I was seeing something like this in [wasm][aot][tests] System.Transactions.Local.Tests failures #50969 where a PNSE would get thrown, but it looked like the exception got ignored, and execution resumed as if nothing had happened

I didn't dig into this much, so I could be wrong!

[radical]

btw, you can run the test in the browser with:
WasmTestAppArgs="-method System.Runtime.CompilerServices.UnsafeTests.NullRef" WasmXHarnessArgs="--no-headless --no-quit" Scenario=WasmTestOnBrowser

And I added WasmXHarnessMonoArgs="--runtime-arg=--trace=E" to get the caught exceptions.

[vargaz]

So there are 2 problems here, the aot compiler is missing a null check, but roslyn also does a bad optimization in release mode.