Add access to exception instance on stack

[Copilot]

Fixes #89724

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[jkotas]

@copilot Can you check the behavior for exceptions that do not inherit from Exception?

[Copilot]

@copilot Can you check the behavior for exceptions that do not inherit from Exception?

I checked. CoreCLR and NativeAOT behaved differently, so I changed NativeAOT to match CoreCLR (0632034):

• CoreCLR: The runtime already wraps a non-Exception object in a RuntimeWrappedException when it is thrown (NormalizeThrownObject). So GetCurrentException() returned that wrapper, the same instance the catch handler sees. WrappedException holds the original object.
• NativeAOT: The runtime never wraps these objects (known issue dotnet/runtimelab#155), so the raw object stays in the ExInfo. Our as Exception turned it into null, which would report "nothing in flight" while something was. Now GetCurrentException wraps the object in a new RuntimeWrappedException. The catch type is the same as CoreCLR, but you get a new wrapper instance on each call.

I also documented this in the API remarks and added a test that throws a string from a DynamicMethod. It passes on CoreCLR (all 12 tests in the class ran). The test needs Reflection.Emit, so it doesn't run on NativeAOT. The NativeAOT change compiles, but I have not run it.

[Copilot]

@copilot Change the design to return exception being caught inside the catch block. CatchHandlerRunningFlag should be unncessary with this change.

Updated the behavior so GetCurrentException() returns the exception being caught and removed CatchHandlerRunningFlag from CoreCLR and NativeAOT. Added catch-handler assertions and updated the API remarks. Commit: 765d3a8a.

[Copilot]

🟡 Changes recommended

The public documentation omits the PlatformNotSupportedException that Mono always throws.

1 open finding

• Document Mono's PlatformNotSupportedException behavior · New

1 resolved since last review

• Alphabetize System.Runtime.ExceptionServices compile items

🧠 Review effort: Balanced