C# : Pass string array to c++ dll / dylib

Question

I'm having trouble passing in an array of strings from my c# code to a function from my c++ dylib.

C# code:

[DllImport("array2d.dylib", EntryPoint = "process_array", CallingConvention = CallingConvention.Cdecl)]
    public static extern int process_array(String[] a, int b);
    static void Main(string[] args)
    {

        String[] list = new String[] { "Abc" , "def", "ghi", "jkl"};
        int josh = process_array(list, 2);                          
     }

My C++ code:

 #include <string>
#include <iostream>



int process_array(char** array, int rows)
{

    std::string s1 ("Array : [");

        for (int i = 0; i < 6; ++i){
                s1.append(array[i]);
                s1.append(", ");

        }
        s1.append("] \n");


        return 1;

}

int main()
{

}

And the error I have been getting is:

Unhandled Exception: System.EntryPointNotFoundException: Unable to find an entry point named 'process_array' in DLL 'array2d.dylib'. at JoshServer.Program.process_array(String[] a, Int32 b)

Any help is appreciated, thanks.

Does your cpp file export any function? There must be some keywords like dllexport. Read about creating dlls in cpp. — Sv Sv
– Sv Sv, Commented Jul 19, 2017 at 13:38

ichramm · Accepted Answer · 2017-07-19 14:44:12Z

1

The function in your C++ program is not being exported:

int process_array(char** array, int rows)

You must mark it with dllexport, like this:

extern "C" int process_array(char** array, int rows)

Update: This project contains the examples used in a talk I gave a while ago about PInvoke, I hope it helps.

Some corrections.

 for (int i = 0; i < 6; ++i){

Should be:

 for (int i = 0; i < rows; ++i){

And

int josh = process_array(list, 2);

Should be

int josh = process_array(list, list.Length);

Updated: Removed __declspec(dllexport) (osx) and added some corrections.

edited Jul 19, 2017 at 14:44

answered Jul 19, 2017 at 13:38

ichramm

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2 Comments

Josh Karol Over a year ago

I'm on a mac and the compiler goes crazy when I add that. From what I read it says to take it out? stackoverflow.com/questions/6838222/…

ichramm Over a year ago

Hi there, sorry I didn't realize you were in a mac. Would you mind trying to add the extern "C" expression to the function?

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