Developers of multithreaded applications should note that:

  o Internal class library data is thread safe; multiple threads can
    access the DEC C++ Class Library simultaneously without compromising
    the integrity of the internal data.

  o The predefined stream objects, cerr, cin, clog, and cout are
    thread safe. However, you need to provide synchronization around
    sequences of operations on these objects. See also: help on
    Predefined_stream_objects_synchronization.

  o User-defined objects are not thread safe; users must provide
    synchronization for such objects if they are shared between threads.
    For more information, see help on the Mutex_package.

  o The ios class member function sync_with_stdio() is not thread safe;
    if your application calls this function, the call must come before
    any threads that use the predefined stream objects: cerr, cin, clog,
    or cout.

  o Generation of error messages within the Vector Package is not
    thread safe; the package uses static data members to handle the current
    error message and there is no synchronization between threads. HP
    recommends that you define a single Mutex object to synchronize all use
    of the Vector Package.

  o The Task Package is not thread safe; only one task can execute at a time.