[API Proposal]: Reflection invoke support for FunctionPointer

[steveharter]

[primarily a placeholder for now for planning]

This adds invoke capability to function pointers, layering on See also #69273.

This will likely create a new MethodSignature class that will have an Invoke() method, analogous to Delegate.DynamicInvoke(https://docs.microsoft.com/dotnet/api/system.delegate.dynamicinvoke) and MethodBase.Invoke(https://docs.microsoft.com/dotnet/api/system.reflection.methodbase.invoke).

This enable dynamic invoke while supporting the CallConv* types for both existing function pointers and ones created dynamically.

Existing function pointers are be obtained from

• typeof(SomeFunctionPointer)
• Type.GetType() if Type is a function pointer
• FieldInfo.GetMethodSignature()
  • The GetMethodSignature() methods are new and only work if the field\property\parameter is a function pointer.
• PropertyInfo.GetMethodSignature()
• ParameterInfo.GetMethodSignature()

A MethodSignature can be created dynamically:

MethodSignature sig = new(
  returnParameter: new MethodSignatureParameter(typeof(bool)),
  parameters: new MethodSignatureParameter[] { new MethodSignatureParameter(typeof(int)) },
  callingConventions = new Type[] {typeof(CallConv.Cdecl)});

The Invoke() takes the function pointer as an IntPtr or void* along with the parameter values:
note that the sample below uses object-based parameters, but is expected to use strongly-typed
TypedReference and collections once that is available to avoid unnecessary allocations and to support by-ref-like types`:

delegate*<int, bool> fn = &MyFunctionPointer;
object retValue = sig.Invoke(fn, new object[] { 42 });

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Issue Details

---

[primarily a placeholder for now for planning]

This adds invoke capability to function pointers, layering on See also #69273.

This will likely create a new MethodSignature class that will have an Invoke() method, analogous to Delegate.DynamicInvoke(https://docs.microsoft.com/dotnet/api/system.delegate.dynamicinvoke) and MethodBase.Invoke(https://docs.microsoft.com/dotnet/api/system.reflection.methodbase.invoke).

This enable dynamic invoke while supporting the CallConv* types for both existing function pointers and ones created dynamically.

Existing function pointers are be obtained from

• typeof(SomeFunctionPointer)
• Type.GetType() if Type is a function pointer
• FieldInfo.GetMethodSignature()
  • The GetMethodSignature() methods are new and only work if the field\property\parameter is a function pointer.
• PropertyInfo.GetMethodSignature()
• ParameterInfo.GetMethodSignature()

A MethodSignature can be created dynamically:

MethodSignature sig = new(
  returnParameter: new MethodSignatureParameter(typeof(bool)),
  parameters: new MethodSignatureParameter[] { new MethodSignatureParameter(typeof(int)) },
  callingConventions = new Type[] {typeof(CallConv.Cdecl)});

The Invoke() takes the function pointer as an IntPtr or void* along with the parameter values:
note that the sample below uses object-based parameters, but is expected to use strongly-typed
TypedReference and collections once that is available to avoid unnecessary allocations and to support by-ref-like types`:

delegate*<int, bool> fn = &MyFunctionPointer;
object retValue = sig.Invoke(fn, new object[] { 42 });

Author:	steveharter
Assignees:	steveharter
Labels:	api-needs-work, area-System.Reflection
Milestone:	8.0.0