Yesterday I needed to write a small C DLL and use it in my C++ sample application. It took some time to figure out how I must do this on my Windows PC with Visual Studio installed.
This is just a little reminder for me, so don't expect too much :-).
C code
The C app contains just a little function:
// ./code/c/lib.c
#include <stdio.h>
__declspec(dllexport) void f()
{
printf("\n This is a C code\n");
}
The keyword __declspec(dllexport)
is only valid within the Microsoft compiler world and exports that function.
Compile C
Open the Visual Studio Developer Command Prompt and navigate to the folder, where the C project is. Then simply type: cl /LD lib.c
. This will create two files. A lib.lib
and a lib.dll
.
C++ Code
Also nothing special. First we need the header file:
// ./code/cpp/Console/Console/Header.h
#pragma once
extern "C" {
__declspec(dllimport) void f();
}
You find declspec
again, but this time it is specified with dllimport
which makes perfectly sense as we are importing our function :-)
Our app:
// ./code/cpp/Console/Console/Console.cpp
#include <iostream>
#include "Header.h"
#pragma comment(lib, "../../../c/lib.lib")
int main()
{
f();
}
Note the line #pragma comment(lib, "../../../c/lib.lib")
which specifies the location of the .lib
so the linker is able to reference the function f()
.
Execute
If you now execute Console.exe
you will get an error because the dll
can not be find. To fix this, just copy the lib.dll
to the folder where Console.exe
is.
Found a typo?
As I am not a native English speaker, it is very likely that you will find an error. In this case, feel free to create a pull request here: https://github.com/gabbersepp/dev.to-posts . Also please open a PR for all other kind of errors.
Do not worry about merge conflicts. I will resolve them on my own.
Top comments (2)
Thanks! I just started to learn C++ to create my own .NET profiler. So more tutorials will come I think.
Thank You