[CoreCLR] Dynamically build custom delegate types to support [Export] #10503
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…into function pointers on CoreCLR
simonrozsival
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grendello and
jonathanpeppers
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This was referenced Sep 19, 2025
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grendello
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Sep 19, 2025
| string delegateTypeName = $"callback_delegate_{EncodeMethodSignature (parameter_type_infos, return_type_info)}"; | ||
| lock (DynamicCallbackFactory.Module) { | ||
| delegate_type = DynamicCallbackFactory.Module.GetType (delegateTypeName) | ||
| ?? CreateDelegateType (delegateTypeName); |
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Can we/should we cache the returned type?
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The type is stored in DynamicCallbackFactory.Module so when we later run into a delegate with the same method signature, the existing delegate type will be reused.
grendello
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Sep 19, 2025
jonathanpeppers
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Fixes #10472
Supersedes #10493 and dotnet/java-interop#1364
The problem is that the Marshal.GetFunctionPointerForDelegate method does not work with delegates with generic types, such as
Action<...>orFunc<...>(context: dotnet/runtime#32963), which was the case of all the delegates created inMono.Android.ExportthroughDynamicMethod.This PR replaces the use of these generic delegate types with dynamically built non-generic types. It is based on an existing implementation in java-interop (see https://github.com/dotnet/java-interop/blob/02bceb03f7c07858590d930ef507745a88200a48/src/Java.Interop.Export/Java.Interop/MarshalMemberBuilder.cs#L274-L311). The CoreCLR is able to marshal the delegates built with these types to function pointers just fine.
In a previous attempt at fixing this issue (#10493), I chose a solution which modified the shape of
JniNativeMethodRegistrationwhich would be an ABI breaking change (dotnet/java-interop#1364). This implementation is much simpler and doesn't cause the same problem. Thanks to @jonpryor for steering me in this direction./cc @jonathanpeppers @grendello