CODEWITHSUNDEEP
c#c++dllimport
jan
jan

Reputation: 875

Issue with std::wstring when calling from c# with DllImport

I was going to call an unmanaged function in a c++ library from c#, but it crashed. While troubleshooting I narrowed it down to std::wstring. A minimal example looks like this:

C++

#include <iostream>

extern "C" __declspec(dllexport) int __cdecl Start()
{
    std::wstring test = std::wstring(L"Hello World");

    return 2;
}

C#

using System.Runtime.InteropServices;

internal class Program
{
    [DllImport("test.exe", CallingConvention=CallingConvention.Cdecl)]
    public static extern int  Start();

    static void Main(string[] args)
    {
        var result = Start();

        Console.WriteLine($"Result: {result}");
    }
}

This gives me a Stack overflow. If I remove the line with std::wstring or I change it to std::string, there is no problem and I get back 2.

Can anyone explain to me what is going on here?

Upvotes: 1

Views: 152

Answers (1)

selbie
selbie

Reputation: 104559

This is something I noticed:

[DllImport("test.exe", CallingConvention=CallingConvention.Cdecl)]

Exporting functions from an EXE instead of a DLL isn't standard. (I think it can be done, but I wouldn't recommend it.)

Build your C++ code as a DLL instead of an EXE. Statically link the DLL with the C++ runtime libraries to avoid missing dependency issues that could arise from not having the right DLLs in the loader search path.

Upvotes: 3

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