Share Global Variable in DLL, feasible or naive?

Question

So the gist is to have a static global variable that can be modified by different executables. For example I have 2 different source files including the same dll.h:

dll.h

#include <iostream>

int globalCounter = 0;

__declspec(dllexport) void incrementCounter() {
    globalCounter++;
    std::cout << globalCounter << '\n';
}

Here are 2 source files that use this dll.h:

/////////// source 1
#include "dll.h"

int main()
{
    incrementCounter();
}

////////// source 2
#include "dll.h"

int main()
{
    for (int i = 0; i < 10; i++)
        incrementCounter();
}

The 2 source files will be compiled to exes and ran. The behavior is that source 2 increments to 10 and source 1 resets to print 1. How can I make it so that first, I run source2 then source1 and source1 prints 11? If this idea is not good, then is there another way of accomplishing what I want without utilizing files? The dll nature of this project HAS to stay.

Answer 1

There will be on instance of the global counter for each executable using the DLL. Therefore each exe will have different values.

There are different ways to do IPC (Inter process Communication), the one you are looking for might be a Shared memory. This lets two processes share a space in the memory. Be really careful if the 2 processes have the right to modify the variable because that can cause some issue...

Answer 2

If not files, then where is the number actually stored?

If you run process A, then quit A, and run B, then everything in memory in A has gone and is inaccessible to B.

On a Windows system, I suppose you could keep it in the registry? Does that count as "not a file" for your thinking?