[ci-fix] Needs review: Marshal mono_ios_* string args as UTF-8 for NativeAOT ILC (refs #130219)

[github-actions]

Workflow artifact: ci-fix
Artifact kind: help
Linked KBE: #130219

Note

AI/Copilot-generated best-effort fix. The root cause and change below are well-supported by the native contract, but I could not run the ILC/NativeAOT tvOS cross-compile in this environment to confirm the compiler error is gone. Please have a mobile/interop owner validate before merging.

Root cause

Every work item on the tvos-arm64 Release AllSubsets_NativeAOT leg (and the other Apple NativeAOT library-test legs enabled by #125437) aborts on startup:

System.Runtime.InteropServices.MarshalDirectiveException: Method
'SimpleTestRunner.mono_ios_set_summary(string)' requires marshalling that is not yet supported by this compiler.
   at SimpleTestRunner.<Main>d__5.MoveNext() in .../AppleTestRunner.cs:line 97

The harness declares the UI-callback p/invokes with default DllImport string marshalling:

[DllImport("__Internal")]
public extern static void mono_ios_append_output (string value);

[DllImport("__Internal")]
public extern static void mono_ios_set_summary (string value);

Default DllImport string marshalling is CharSet.Ansi. Under Mono AOT this was tolerated, but the ILC (NativeAOT) compiler rejects it here with MarshalDirectiveException. Native symbol resolution itself is fine — #125437 wires DirectPInvoke __Internal so mono_ios_set_summary resolves statically — the failure is purely the marshalling directive, so the process fails before the first test runs.

Attempted fix

Annotate both string parameters with [MarshalAs(UnmanagedType.LPUTF8Str)]. This is not an arbitrary choice: the native implementations in src/tasks/AppleAppBuilder/Templates/main-console.m take const char* and immediately call [NSString stringWithUTF8String:value], i.e. they expect a UTF-8 C string. So LPUTF8Str:

• matches the real native contract exactly (the previous ANSI default was also semantically wrong for any non-ASCII test name), and
• gives ILC an explicit, supported marshalling directive instead of the unsupported implicit one.

These are test-harness display hooks (they update the on-device summary/output UI); no test logic or assertion is changed, and nothing is skipped or disabled.

What is unverified / where I need help

• I could not run the NativeAOT ILC compile for the tvOS/iOS leg locally, so I have not empirically confirmed the MarshalDirectiveException is eliminated. Please confirm that LPUTF8Str on a DirectPInvoke __Internal import compiles under ILC for these legs.
• If the team would rather convert these to source-generated [LibraryImport] marshalling for NativeAOT correctness, that is a reasonable alternative — this PR takes the minimal directive-only approach.

Validation

• Command: NativeAOT/ILC tvOS cross-compile of AppleTestRunner — not run because the Apple NativeAOT toolchain and cross-compile exceed this environment's capabilities/time budget.
• Result: not run. Change is a marshalling-attribute-only edit; UnmanagedType.LPUTF8Str and System.Runtime.InteropServices are already in scope in the file.

Evidence

• Failing build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1493986 (follow-up 1494308 reproduces on the same leg)
• Introduced by: [mobile] Enable NativeAOT library tests on Apple mobile platforms #125437 ("[mobile] Enable NativeAOT library tests on Apple mobile platforms", merged 2026-07-02), whose own description notes it statically resolves mono_ios_set_summary via DirectPInvoke __Internal — high confidence this is the surfacing change.
• Native contract: src/tasks/AppleAppBuilder/Templates/main-console.m lines ~107-121 (const char* + stringWithUTF8String).

Help wanted

• Likely author of the enabling change: @kotlarmilos ([mobile] Enable NativeAOT library tests on Apple mobile platforms #125437)
• Interop / NativeAOT marshalling: @jkoritzinsky, @dotnet/ilc-contrib

Suggested reviewers / area contacts

• area-NativeAOT-coreclr: @agocke, @dotnet/ilc-contrib
• Apple mobile (os-ios): @kotlarmilos, @steveisok

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Filed by ci-failure-fix. Comment here or on the workflow file to suggest changes; ci-failure-scan-feedback reads in-scope feedback daily and opens (or updates) a PR with prompt edits.

Note

🔒 Integrity filter blocked 6 items

The following items were blocked because they don't meet the GitHub integrity level.

• #128501 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #104998 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #104750 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• #97491 search_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• [ci-scan] Test failure: AsyncProfilerTests.StateMachineAsync_CallstackStressWithVaryingDepths under libraries-jitstress #129938 issue_read: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• [ci-scan] Test failure: System.Threading.Tests.MutexTests.CrossProcess_NamedMutex_ConcurrentCreateOrOpen #130125 issue_read: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".

To allow these resources, lower min-integrity in your GitHub frontmatter:

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Generated by CI Outer-Loop Failure Fixer · ● 9.2M · ◷

[dotnet-policy-service]

Tagging subscribers to this area: @agocke, @dotnet/ilc-contrib
See info in area-owners.md if you want to be subscribed.

[MichalStrehovsky]

/azp run runtime-extra-platforms

[MichalStrehovsky]

I would be surprised if this fixes anything. Without this annotation, it should marshal as an ansi string, not throw this exception. This exception is very unexpected.

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