Reference Guide

ZCOM C I/F Library Routines
ZSEND (3X)
Chapter 4308
cancellation point Thread cancellation can occur when a thread
calls this routine.
async-cancel unsafe The calling thread’s cancelability type must be
PTHREAD_CANCEL_DEFERRED if
cancellation is enabled.
async-signal unsafe It cannot be called from a signal handler.
fork unsafe It cannot be called by a child process after
fork(2) but before exec(2).