/******************************************************** * An example source module to accompany... * * "Using POSIX Threads: Programming with Pthreads" *     by Brad nichols, Dick Buttlar, Jackie Farrell *     O'Reilly & Associates, Inc. * ******************************************************** * async_safe -- * * Example showing macro wrappers for calling non-async * safe routines when the caller has asynchronous  * cancellation turned on */#include <stdlib.h>#include <stdio.h>#include <unistd.h>#include <fcntl.h>#include <sys/types.h>#include <sys/stat.h>#include <pthread.h>#define async_cancel_safe_read(fd,buf,amt) \   { \      int oldtype; \      pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype); \      if (read(fd,buf,amt) < 0) \         perror("read"),exit(1); \      pthread_setcanceltype(oldtype,NULL); \      pthread_testcancel(); \   }    #define async_cancel_safe_write(fd,buf,amt) \   { \      int oldtype; \      pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype); \      if (write(fd,buf,amt) < 0) \         perror("write"), exit(1); \      pthread_setcanceltype(oldtype,NULL); \      pthread_testcancel(); \   }static int fd;   void *io(void *arg){   int *fd=(int *)arg;    char buf[20]="String";   int amt=20;   for (;;) {      async_cancel_safe_write(*fd,buf,amt);      async_cancel_safe_read(*fd,buf,amt);   }   return(NULL);}void *killer(void *arg){    pthread_t * target = (pthread_t *)arg;   int rtn;   sleep(1);   pthread_cancel(*target);   return(NULL);}extern intmain(void){   int rtn;   pthread_t io_thread, killer_thread;      pthread_t t1;   extern int fd;     extern void *io(void *);   extern void *killer(void  *);   if ((fd = open(".ktemp",O_CREAT | O_RDWR, 0666)) < 0)      perror("open"), exit(1);   pthread_create(&io_thread, 		  NULL,		  io,		  (void *)&fd);   pthread_create(&killer_thread,		  NULL,		  killer,		  (void *)&io_thread);   pthread_join(io_thread, NULL);   pthread_join(killer_thread,NULL);   if ((close(fd)) < 0)     perror("close"),exit(1);   if ((unlink(".ktemp")) < 0)     perror("unlink"),exit(1);   return 0;}