/sys$common/syshlp/helplib.hlb DCE_THREADS, Application Routines, pthread_cancel  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  NAME

  pthread_cancel - Allows a thread to request that it or another thread
                   terminate execution

  SYNOPSIS

      #include <pthread.h>

      int pthread_cancel(pthread_t thread);

  PARAMETERS

      thread                Thread that receives a cancel request.

  DESCRIPTION

  The pthread_cancel() routine sends a cancel to the specified thread. A
  cancel is a mechanism by which a calling thread informs either itself or
  the called thread to terminate as quickly as possible. Issuing a cancel
  does not guarantee that the canceled thread receives or handles the can-
  cel. The canceled thread can delay processing the cancel after receiving
  it. For instance, if a cancel arrives during an important operation, the
  canceled thread can continue if what it is doing cannot be interrupted
  at the point where the cancel is requested.

  Because of communications delays, the calling thread can only rely on
  the fact that a cancel eventually becomes pending in the designated
  thread (provided that the thread does not terminate beforehand). Furth-
  ermore, the calling thread has no guarantee that a pending cancel is to
  be delivered because delivery is controlled by the designated thread.

  Termination processing when a cancel is delivered to a thread is similar
  to pthread_exit(). Outstanding cleanup routines are executed in the con-
  text of the target thread, and a status of -1 is made available to any
  threads joining with the target thread.

  This routine is preferred in implementing Ada's abort statement and any
  other language (or software-defined construct) for requesting thread
  cancellation.

  The results of this routine are unpredictable if the value specified in
  thread refers to a thread that does not currently exist.

  RETURN VALUES

  If the function fails, errno may be set to one of the following values:

    Return   Error      Description
    ____________________________________________________
    0                   Successful completion.

    -1      [EINVAL]    The specified thread is invalid.

    -1      [ERSCH]     The specified thread does not refer
                        to a currently existing thread.

  RELATED INFORMATION

      FUNCTIONS: pthread_exit
                 pthread_join
                 pthread_setasynccancel
                 pthread_setcancel
                 pthread_testcancel