...

extern "C" {
   // Set value XXXXX to true
   __declspec(dllexport) void SetValueXXXXXToTrue() {}
}

...

int main(int argc, char **argv) {
  // prevent compiler from optimizing out argument passing...
  if (!argv) {
    return (int)(long)&SetValueXXXXXToTrue;
  }
  ...
}

void TargetFunction() {
   // Check arguments user has passed.
   bool XXXXX = dlsym(RTLD_DEFAULT, "SetValueXXXXXToTrue");
   if (XXXXX) {
     ....
   }
}