The ZOOM ErrorLogger Package:

If you change the ostream associated with an ELoutput destination, you need to be careful to avoid this ways of shooting yourself in the foot:

Leaving two active handles to the same file

Say your code looks as follows:

  ELadministrator logger = ELadministrator::instance();
  std::ostream os1("thisFile");
  ELoutput output (os1);
  logfile = logger->attach(output);
  logfile.changeFile("thisFile");
  

What you have done is to create two std::ostreams refering to the same actual file, exactly as if you had done

  std::ostream os1("thisFile");
  std::ostream os2("thisFile");
  

os1 has not been deleted and remains completely accessible. If you stream data to os1 and also send messages to logfile there will be a clash, and unpredictable behavior.