gistfile1.hpp

const char *pluginSignature = "my.super.expensive.plugin";
  
#ifdef APL
  // Mac-specific: it IS possible to have  plugin installed twice, once in the ACF folder
  // and once in the X-System folder. Probably due to namespace mangling on OS X
  // the system will NOT crash the app when the plugin gets loaded twice. 
  // Thus, we query the enabled plugins for the defined signatures
  // and DO NOT activate should the other plugin already be plugged in
  
  XPLM_API XPLMPluginID other_copy_id = XPLMFindPluginBySignature(pluginSignature);
  if(-1 != other_copy_id) {
      // Figure out where the other plugin came from
      char pathToAnotherCopy[256];
      XPLMGetPluginInfo(other_copy_id, NULL, pathToAnotherCopy, NULL, NULL);
      XPLMDebugString("another copy already loaded from \n");
      XPLMDebugString(pathToAnotherCopy);
      return 0;
  }
#endif