cpp_cli

C++/CLI

Description

C++/CLI is probably one of the most standard ways to implement interaction between C# and C++. In fact, the library on C++/CLI is a router that takes responsibility for raising Runtime and calling managed code.

Pros

1. Easy to implement
2. Lots of documentation
3. Takes care of some of the type marshalling issues
4. Supports all .NET Runtimes

Cons

1. Requires C++ compiler for assembly
2. Additional code layer in the form of .dll library in C++
3. Requires .NET Runtime installed
4. Only for Windows machine

Useful links

1. .NET programming with C++/CLI
2. C++/CLI

Projects

The example consists of 3 projects:

1. CppCli.Api - a library on .NET
2. CppCli.Wrapper - a library on C++/CLI aka wrapper
3. CppCli.Client - a client of the library

CppCli.Api

Standard library in .NET with API provided by Api.cs

public static class Api
{
    public static int Calculate(int a, int b) => a + b;
}

CppCli.Wrapper

A C++ wrapper library that consists of 2 files to represent the native API

// Api.h
#define EXTERN_DLL_EXPORT extern "C" __declspec(dllexport)

EXTERN_DLL_EXPORT int calculate(int a, int b);

// Api.cpp
#include "Api.h"

int calculate(int a, int b)
{
    return CppCli::Api::Api::Calculate(a, b);
}

CppCli.Client

A client for working with the wrapper library, which consists of one .cpp file. The main method is called call_library, which is responsible for loading and calling the method from the wrapper library

void call_library(const std::string& file_name)
{
    const std::wstring name(file_name.begin(), file_name.end());
    const auto library_handle = LoadLibrary(name.c_str());

    if (library_handle == nullptr)
    {
        std::cout << "Cannot open library by path '" << file_name << "'\n";
        return;
    }

    std::cout << "Success LoadLibrary(\"" << file_name << "\")\n";

    const auto proc_name = "calculate";
    const auto proc_address = (proc)GetProcAddress(library_handle, proc_name);

    if (proc_address == nullptr)
    {
        std::cout << "Cannot get proc '" << proc_name << """' in file '" << file_name << "'\n";
        return;
    }

    std::cout << "Success GetProcAddress(\"" << proc_name << "\")\n";

    std::cout << "Calculation result is " << proc_address(1, 1) << '\n';
}

Assembly

The project is built from any IDE or console. As a result, 3 files CppCli.Api.dll, CppCli.Wrapper.dll, CppCli.Client.exe will be obtained

Executing files

If you call dumpbin /exports on the wrapper library, you can get the following output, where you can see that the Calculate method we defined is available for export.

Dump of file CppCli.Wrapper.dll

File Type: DLL

  Section contains the following exports for CppCli.Wrapper.dll

    00000000 characteristics
    FFFFFFFF time date stamp
        0.00 version
           1 ordinal base
           1 number of functions
           1 number of names

    ordinal hint RVA      name

          1    0 00005000 calculate = calculate

  Summary

        1000 .data
        1000 .nep
        1000 .pdata
        F000 .rdata
        1000 .reloc
        1000 .rsrc
        4000 .text

If we call dumpbin /exports for the .NET library, we will not see a single export.

Dump of file CppCli.Api_net9.0.dll

File Type: DLL

  Summary

        2000 .reloc
        2000 .rsrc
        2000 .text

When running .exe you may get the following output:

Success LoadLibrary("CppCli.Wrapper.dll")
Success GetProcAddress("calculate")
Calculation result is 2