System.NullReferenceException in System.Runtime.Intrinsics.Vector256.get_IsHardwareAccelerated()

[rolfbjarne]

This is the failure:

Introspection.ApiCMAttachmentTest
	[PASS] CheckAttachments
	[FAIL] CheckFailAttachments : System.NullReferenceException : Object reference not set to an instance of an object.
		   at System.Runtime.Intrinsics.Vector256.get_IsHardwareAccelerated()
		   at System.SpanHelpers.IndexOf(Byte& searchSpace, Int32 searchSpaceLength, Byte& value, Int32 valueLength)
		   at System.Security.Cryptography.PemEncoding.IndexOfByOffset[TChar](ReadOnlySpan`1 str, ReadOnlySpan`1 value, Int32 startPosition)
		   at System.Security.Cryptography.PemEncoding.TryFindCore[TChar,T](ReadOnlySpan`1 pemData, PemFields& fields)
		   at System.Security.Cryptography.PemEncoding.TryFindUtf8(ReadOnlySpan`1 pemData, PemFields& fields)
		   at System.Security.Cryptography.PemEnumerator`1.Enumerator.MoveNext()
		   at System.Security.Cryptography.X509Certificates.AppleCertificatePal.TryDecodePem(ReadOnlySpan`1 rawData, Func`3 derCallback)
		   at System.Security.Cryptography.X509Certificates.X509Pal.AppleX509Pal.GetCertContentType(ReadOnlySpan`1 rawData)
		   at System.Security.Cryptography.X509Certificates.X509Certificate2.GetCertContentType(ReadOnlySpan`1 rawData)
		   at System.Security.Cryptography.X509Certificates.X509CertificateLoader.LoadCertificatePal(ReadOnlySpan`1 data)
		   at System.Security.Cryptography.X509Certificates.X509CertificateLoader.LoadCertificate(ReadOnlySpan`1 data)
		   at System.Security.Cryptography.X509Certificates.X509CertificateLoader.LoadCertificate(Byte[] data)
		   at Introspection.ApiCMAttachmentTest.GetINativeInstance(Type t) in /Users/rolf/work/dotnet/macios/mono-master/macios/tests/introspection/ApiCMAttachmentTest.cs:line 406
		   at Introspection.ApiCMAttachmentTest.CheckFailAttachments() in /Users/rolf/work/dotnet/macios/mono-master/macios/tests/introspection/ApiCMAttachmentTest.cs:line 576
		   at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
		   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)

This regressed in #25583.

Old analysis

Which happens when running the Mac Catalyst introspection tests on x64 from the net11.0 branch.

This looks identical too dotnet/runtime#128901, except that setting DOTNET_MaxVectorTBitWidth=128 does not fix it.

There are also a number of other confusing factors:

• This particular scenario fails in CI, but only sometimes.

  Failed here:

  • https://vsdrop.corp.microsoft.com/file/v1/macios/device-tests/20260617.53/14405705//mac_14_x64mac_sonoma-1/;/tests/vsdrops_index.html
    • PR: [DRAFT] [net11.0] [assembly-preparer] Create a new tool to eventually replace custom linker steps. #25651 (comment)
    • https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14405705&view=logs&j=623bc498-120b-5ff2-984a-5b073efffe1b&t=4a2ee696-2483-5c21-b74f-dbb45ac9f281
  • https://vsdrop.corp.microsoft.com/file/v1/macios/device-tests/20260617.38/14404020//mac_14_x64mac_sonoma-4/;/tests/vsdrops_index.html
    • PR: [net11.0] Merge main into net11.0. #25526 (comment)
    • https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14404020&view=logs&jobId=224d5c53-1ab2-5daa-dc39-ac047acc0ab9&j=224d5c53-1ab2-5daa-dc39-ac047acc0ab9&t=ae9bfd53-987b-58f1-46b2-59bd6cc2d646&s=4bef80fe-6bf2-5d05-9ea7-d49be9fa9895

  Passed here:

  • https://vsdrop.corp.microsoft.com/file/v1/macios/device-tests/20260616.3/14388005//mac_14_x64mac_sonoma-1/;/tests/vsdrops_index.html
    • 8c02050#commitcomment-188942215
    • https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14388005&view=logs&j=623bc498-120b-5ff2-984a-5b073efffe1b&t=4a2ee696-2483-5c21-b74f-dbb45ac9f281
  • https://vsdrop.corp.microsoft.com/file/v1/macios/device-tests/20260618.2/14412650//mac_14_x64mac_sonoma-1/;/tests/vsdrops_index.html
    • PR: [net11.0] Update dependencies from dotnet/dotnet #25694 (comment)
    • https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14412650&view=logs&j=40204f43-a3f0-57de-7742-2d8168f82492&t=ffb383a3-4a1e-58d1-3c35-46e1fa75b8ea

• I can reproduce the failure locally if I build on my arm64 device (Apple M2 Pro), and copy the test app to my x64 device (iMac Pro 3,2 Ghz 8-Core Intel Xeon W).

• If I download the apps built on CI, the ones that pass on CI pass locally too, and the ones that fail on CI fail locally too. This seems to indicate it's a build-time issue, and not a runtime issue.

• If I compare the binlogs between the working CI builds and the failing local builds, I can't see any difference.

• There doesn't seem to be any difference between the bots that built the working apps and the bots that built the failing apps.

[davidnguyen-tech]

Do we know what exactly is causing this failure? Is it because the test is trying to use a method from the BCL and expects it to be R2R-compiled, but it can't find it?

The way #25583 was implemented in the end was because the iOS runtime packs are R2R-compiled in dotnet/runtime.

Perhaps we could disable R2R-compilation of the iOS runtime packs in dotnet/runtime directly, since we re-run R2R compilation for both Release and Debug builds anyway.

It would then also simplify enabling R2R only on CoreLib here in dotnet/macios.

[kotlarmilos]

This looks like a runtime bug. The NRE shouldn't be a missing IL body. Compiled R2R code has its vector-width choice decided at build time, but interpreted code performs lookup at runtime and sees AVX2=true on x64, and takes the 256-bit Vector256 path that it can't execute.

[kotlarmilos]

@rolfbjarne Does this require x64 hardware or could be validated on Rosseta as well? Created a tentative fix in dotnet/runtime#129574

[rolfbjarne]

@rolfbjarne Does this require x64 hardware or could be validated on Rosseta as well? Created a tentative fix in dotnet/runtime#129574

It requires x64 hardware, it doesn't fail with Rosetta.