[NativeAOT] How can I implement dynamic internal calls(or Qcall) in my custom NativeAOT runtime?

[TickThunder]

I'm trying to implement Mono's add_internal_call API and the invocation of internal calls. I'm confused about how NativeAOT achieves internal call invocation. My idea is to modify the ILC's ILEmitter, similar to TypeSystemThrowingILEmitter, to generate native method calls. However, emitting IL is a bit difficult for me. Does anyone have any good suggestions?

[AustinWise]

Have you forked this repository and modified the runtime to have a new internal calls or qcalls? Or are you trying to statically linking to a library that is not defined in dotnet/runtime? The second is more common and documented, so I'll answer it first.

Generating direct calls for P/Invokes

See this article. Rather than allowing the .NET Runtime to lazily load shared libraries (.DLLs) when using P/Invoke, you can have the native linker either dynamically or statically link the final executable against native libraries.

Defining a new internal call in a custom NativeAOT runtime

This is only something you should do if you are forking this repository (dotnet/runtime) in order to add a new .NET runtime feature. It is much easier to use the method defined in the previous section, if possible.

I'll use an existing internal call, RhRegisterGcCallout, to illustrate how an internal call is defined in used. On the native side, use one of the FCIMPL macros to define the function. The number at the end of the FCIMPL macro is the number of parameters the function takes:

FCIMPL2(FC_BOOL_RET, RhRegisterGcCallout, GcRestrictedCalloutKind eKind, void * pCallout)
{
    // ...
}
FCIMPLEND

In the C# side, you use the RuntimeImport attribute to define the function:

[MethodImplAttribute(MethodImplOptions.InternalCall)]
[RuntimeImport(RuntimeLibrary, "RhRegisterGcCallout")]
internal static extern bool RhRegisterGcCallout(GcRestrictedCalloutKind eKind, IntPtr pCalloutMethod);

(RuntimeLibrary is a single asterisk)

Note that while the RuntimeImportAttribute is not public, the compiler matches by name. So you can define your own copy of RuntimeImportAttribute in your own code. For an example of calling a RuntimeImport function from outside of System.Private.CoreLib, see this repository. The from-dotnet-runtime directory contains the RuntimeImportAttribute and other code copied from the NativeAOT runtime.

Important note: if you are doing nothing in your internal call the blocks for any amount of time, you should use a QCALL instead. This will ensure that the garbage collector can suspend threads in a timely manner. See RhWaitForPendingFinalizers for an example of something implemented as a QCALL.

[TickThunder]

Thank you for your reply.
'dynamic' I mean runtime dynamic. I want to execute C++ functions in C# by obtaining their function pointers through another function(like mono_add_internal_call).
and I also want to know how RuntimeImportMethodNode is used in ILC / RyuJIT. I have not been able to find the corresponding source code.