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

  NAME

      pthread_setasynccancel - Enables or disables the current
                               thread's asynchronous cancelability

  SYNOPSIS

      #include <pthread.h>

      int pthread_setasynccancel( int state );

  PARAMETERS

      state                State of asynchronous cancelability set for
                           the calling thread.  On return, receives the
                           prior state of asynchronous cancelability.
                           Valid values are as follows:

                           CANCEL_ON     Asynchronous cancelability is
                                         enabled.

                           CANCEL_OFF    Asynchronous cancelability is
                                         disabled.

  DESCRIPTION

  The pthread_setasynccancel()  routine enables or disables the current
  thread's asynchronous cancelability and returns the previous cancelabil-
  ity state to the state parameter.

  When general cancelability is set to CANCEL_OFF, a cancel cannot be
  delivered to the thread, even if a cancelable routine is called or asyn-
  chronous cancelability is enabled. When general cancelability is set to
  CANCEL_ON, cancelability depends on the state of the thread's asynchro-
  nous cancelability.

  When general cancelability is set to CANCEL_ON and asynchronous cancela-
  bility is set to CANCEL_OFF, the thread can only receive a cancel at
  specific cancellation points (for example, condition waits, thread
  joins, and calls to the pthread_testcancel() routine). If both general
  cancelability and asynchronous cancelability are set to CANCEL_ON, the
  thread can be canceled at any point in its execution.

  When a thread is created, the default asynchronous cancelability state
  is CANCEL_OFF.

  If you call this routine to enable asynchronous cancels, call it in a
  region of code where asynchronous delivery of cancels is disabled by a
  previous call to this routine. Do not call threads routines in regions
  of code where asynchronous delivery of cancels is enabled.  The previous
  state of asynchronous delivery can be restored later by another call to
  this routine.

  RETURN VALUES

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

    Return       Error      Description
    ___________________________________________________________
    CANCEL_ON               Asynchronous cancelability was on.

    CANCEL_OFF              Asynchronous cancelability was off.

    -1          [EINVAL]    The specified state is not CANCEL_ON
                            or CANCEL_OFF.

  RELATED INFORMATION

      FUNCTIONS: pthread_cancel
                 pthread_setcancel
                 pthread_testcancel