[C] Use Windows mutex to create a single instance app

one-instance.cpp

#include <windows.h>

int main(int argc, char *argv[])
{
    // ensure only one running instance
    HANDLE hMutexHandle = CreateMutex(NULL, TRUE, L"my.mutex.name");
    if (GetLastError() == ERROR_ALREADY_EXISTS)
    {
        return 0;
    }
    
    // rest of the program
    
    ReleaseMutex(hMutexHandle);
    CloseHandle(hMutexHandle);
    
    return 0;
}