Third paty dll management

Development Programming & Scripting C++
1

Hello,
Right now I am trying to learn how to load third party libraries in a correct way. For test purpose I have build two dll, one in C# that does the logic, one in c++ CLR with dllexport that wraps around the .NET library

The C# library code


namespace NumGenerator
{
    public static class NumGen
    {
        public static int] GenerateNumbers()
        {
            int] res = new int[100];
            for(int i = 0; i < res.Length; i++)
            {
                res* = i * i;
            }
        return res;
        }
   }
}

C++ h file


#pragma once
extern "C" {

__declspec(dllexport) void __cdecl GetNumbers(int* nums, int& count);

}

C++ cpp file


#include <memory>

void __cdecl GetNumbers(int* nums, int& count)
{
    array<int>^ numsManaged = NumGenerator::NumGen::GenerateNumbers();
    pin_ptr<int> numNative = &numsManaged[0];
    int* res = numNative;
    count = numsManaged->Length;
    std::memcpy(nums, res, sizeof(int) * count);
}

And then I call it in plugin


 //typedef void (*GetNumFunc)(int*, int&);
FString LibraryPath = TEXT("NativeClrLibrary.dll");

void* handle = FPlatformProcess::GetDllHandle(*LibraryPath);
GetNumFunc getNum = (GetNumFunc)FPlatformProcess::GetDllExport(handle, L"GetNumbers");
if (getNum != NULL) {
    int a[200];
    int count;
    getNum(a, count);
}

I am loading the c++ dll in a plugin that loads c# dll, but I managed it only in a very specific way, I can’t seem to find any information on this topic and it would be great if someone would clarify.

  1. How is Build.cs connected with dlls? I tried adding to PublicRuntimeLibraryPaths, RuntimeDependencies, PublicDelayLoadDLLs but none of them did affect the result in any way. It still only loads if dll is in Binaries folder or a full path is specified. Is there any way i can change the lookup path (setting PATH vatiable doesn’t do anything either)?
  2. The second one was very tricky. It turned out that lookup path for c++ dll was different than FPlatformProcess::GetDllHandle, it looked only in Engine/Binaries directory,so I had to copy the C# dll there, so my C++ dll could link to it. When I did all these steps, the code worked, but it doesn’t seem the right solution to me.
  3. What is the proper way to install dlls from a plugin? I have found people simply copying libraries using the Build.cs file. Is there any other advised method for doing such things.

With the method I’m stuck right now I can’t understand how should I structure my future plugin, so that other people could use it in their projects and how will it work in release where no Engine folder exists?