Well I want to make a DLL but all of the tutorials online seem to focus tword GUI programing or go a little too fast. Can anyone explain it? As far as I have seen it's syntax resembles resource files. And what makes it a 'Dynamic Link Libray' as in what makes it dynamic?
Oh I want to use this for console app.

Recommended Answers

All 3 Replies

First of all, this thread should answer all your questions about what a DLL is and what is meant by "dynamic-link".

Now, for a simple example of a DLL, here is the simplest example I can think of, the "hello world" program:

In hello_world.h:


#define DLL_FUNCTION extern "C" __declspec(dllexport)
#define DLL_FUNCTION extern "C" __declspec(dllimport)

DLL_FUNCTION void printHelloWorld();


In hello_world.cpp:


#include "hello_world.h"
#include <iostream>

DLL_FUNCTION void printHelloWorld() {
  std::cout << "Hello World!" << std::endl;

In main.cpp:

#include "hello_world.h"

int main() {
  return 0;

Now, you must compile the "hello_world.cpp" as a DLL and then compile the "main.cpp" as an executable, linking it with the import library of the DLL.

If you are using MinGW GCC, then you can do this:

g++ hello_world.cpp -shared -o hello_world.dll --out-implib libhello_world.a
g++ main.c -o main.exe -lhello_world

If you are using MSVC, then you should just create one "DLL" project with the "hello_world.cpp" file as the source file. And then, create one executable project with the main.cpp file. You need to first compile the DLL project (as "hello_world.dll"), then add the "hello_world.lib" to your link-libraries in your executable's project settings (build options), and then compile the executable. Or, equivalently in command-line:

cl -o hello_world.dll hello_world.cpp /link /DLL
cl -o main.exe main.cpp hello_world.lib

I'm pretty sure the above will work.

One last tiny question: Does

using namespace std;

work in a DLL? I have heard that there are certin conditions where it can't be used.

It works anywhere, but it _should_ not be used in a header file. The motivation is essentially that you don't want it to have repercussions on the code that includes that header file (i.e. the user of the header file might not want to import the std namespace, so you should never do it in a header file). So, the guideline is that if you want to use "using namespace std;" in your code, you have to restrict it only to cpp files, and thus, in the header files, you have to use the full qualifications like "std::string" or "std::cout".

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.