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nukleer bomb

•Created by nukleer bomb on 2/10/2023 in #help

❔ `delegate*` wrapper throws `System.BadImageFormatException`

I wrote some wrapper for delegate* unmanaged to use it in F# since it doesn't support function pointers:

using Microsoft.FSharp.Core;

public unsafe struct FuncPtr<TArg, TRet>
{
    private readonly nint ptr;

    public FuncPtr(nint ptr) => this.ptr = ptr;

    public TRet Call(TArg arg)
    {
        if (typeof(TRet) == typeof(Unit))
        {
            if (typeof(TArg) == typeof(Unit))
                ((delegate* unmanaged<void>)ptr)();
            else
                ((delegate* unmanaged<TArg, void>)ptr)(arg);

            return default!;
        }
        else
        {
            return typeof(TArg) == typeof(Unit) ? 
                ((delegate* unmanaged<TRet>)ptr)() : 
                ((delegate* unmanaged<TArg, TRet>)ptr)(arg);
        }
    }
}

using Microsoft.FSharp.Core;

public unsafe struct FuncPtr<TArg, TRet>
{
    private readonly nint ptr;

    public FuncPtr(nint ptr) => this.ptr = ptr;

    public TRet Call(TArg arg)
    {
        if (typeof(TRet) == typeof(Unit))
        {
            if (typeof(TArg) == typeof(Unit))
                ((delegate* unmanaged<void>)ptr)();
            else
                ((delegate* unmanaged<TArg, void>)ptr)(arg);

            return default!;
        }
        else
        {
            return typeof(TArg) == typeof(Unit) ? 
                ((delegate* unmanaged<TRet>)ptr)() : 
                ((delegate* unmanaged<TArg, TRet>)ptr)(arg);
        }
    }
}

But when I try to call Call() method:

using KiDev.IlAsm.FuncPtr;
using Microsoft.FSharp.Core;
using System.Runtime.InteropServices;

unsafe
{
    delegate* unmanaged<int> x = &Test;
    Console.WriteLine($"delegate* = {x()}"); // fine 

    var ptr = new FuncPtr<Unit, int>((nint)x);
    Console.WriteLine($"FuncPtr = {ptr.Call(null!)}"); // exception
}

[UnmanagedCallersOnly]
static int Test() => 12;

using KiDev.IlAsm.FuncPtr;
using Microsoft.FSharp.Core;
using System.Runtime.InteropServices;

unsafe
{
    delegate* unmanaged<int> x = &Test;
    Console.WriteLine($"delegate* = {x()}"); // fine 

    var ptr = new FuncPtr<Unit, int>((nint)x);
    Console.WriteLine($"FuncPtr = {ptr.Call(null!)}"); // exception
}

[UnmanagedCallersOnly]
static int Test() => 12;

I get System.BadImageFormatException: "Bad element type in SizeOf.". What I am doing wrong?

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