How to make a callback global so I can use it to other functions?

Question

I declared a function like this:

int __stdcall DoSomething(int &inputSize, int &outputSize, void(* __stdcall progress)(int) )
{
}

How can I make progress() callback a global variable to use it in other functions in the same DLL? I am a newbie to C++.

Answer 1

Create a function with a matching signature (i.e., void (*)(int)).

#include <iostream>

//void (      *      )(     int    ) - same signature as the function callback
  void progressHandler(int progress)
{
    std::cout << "received progress: " << progress << std::endl;
}

int DoSomething(int &inputSize, int &outputSize, void (*progress)(int))
{
    progress(100);
    return 0;
}

int main()
{
    int inputSize = 3;
    int outputSize = 3;
    DoSomething(inputSize, outputSize, progressHandler);

    return 0;
}

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Output:

received progress: 100

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Even though I removed it (because I used g++) you can keep the __stdcall.