/******************************************************** * An example source module to accompany... * * "Using POSIX Threads: Programming with Pthreads" *     by Brad nichols, Dick Buttlar, Jackie Farrell *     O'Reilly & Associates, Inc. * ******************************************************** * sig.c * * Simple example of pthreads and signals. */#include <stdlib.h>#include <stdio.h>#include <unistd.h>#include <signal.h>#include <sys/types.h>#include <pthread.h>#define MAX_NUM_THREADS  10void *catch_usr1(void *p){  int signo=SIGUSR1;  struct sigaction action;  int caught;  sigset_t  sigs_to_catch;  /* Identify our thread */  printf("\ncatchit() signal %d processing running as thread 0x%x \n", 	 signo, pthread_self());  printf("Someone please send pid %d a SIGUSR1\n", getpid());  /*   * We inherited a thread sigmask with all the signals    * blocked.  So, we can wait on whatever signals we're   * interested in and (as long as no other thread waits   * for them) we'll be sure return from sigwait() to   * handle it.   */   /* set this thread's signal mask to block out all other signals */  sigemptyset(&sigs_to_catch);  sigaddset(&sigs_to_catch, signo);  sigwait(&sigs_to_catch, &caught);  printf("\ncatchit() signal %d processing thread caught signal %d\n",          signo, caught);  return(NULL);}void bugcatcher(int sig) {  printf("The BUGCATCHER caught signal %d in thread 0x%x\n", 	 sig, pthread_self());  pthread_exit(0);}void *cause_sig_sync(void *p){  int i, id;  sigset_t sigs_to_catch;  /* Identify our thread */  printf("cause_sig_sync() running in thread 0x%x\n", pthread_self());   /* set this thread's signal mask to block out all other signals */  sigemptyset(&sigs_to_catch);  sigaddset(&sigs_to_catch, SIGSEGV);  sigaddset(&sigs_to_catch, SIGBUS);  pthread_sigmask(SIG_UNBLOCK, &sigs_to_catch, NULL);  /* Loop simulating useful processing in this thread */  for(i=1;i==i;i++) {    printf("printing count: %4d\r",i);    if (i%100 == 0) {      id = *(int *)p; /* Guaranteed bad address */    }  }  return(NULL); }extern intmain(void){  int       i;  pthread_t threads[MAX_NUM_THREADS];  int       num_threads = 0;  sigset_t  sigs_to_block;  struct    sigaction action;  /* Identify our thread */  printf("main() running in thread 0x%x\n", pthread_self());   /*    * Set this thread's signal mask to block out all other signals   * Other thread's will inherit the mask   */  sigfillset(&sigs_to_block);  pthread_sigmask(SIG_BLOCK, &sigs_to_block, NULL);  /* Set signal handler for catching SIGSEGV and SIGBUS */  action.sa_handler=bugcatcher;  sigaction(SIGSEGV, &action, NULL);  sigaction(SIGBUS, &action, NULL);  /* spawn the threads */     /* Make sure we can catch synchronous signals as exceptions */  pthread_create(&threads[num_threads++],		 NULL,                 cause_sig_sync,		 NULL);    /* Rather than install the action/handler for the process,     we create a thread to wait for the signal */  pthread_create(&threads[num_threads++],		 NULL,                 catch_usr1,		 NULL);  printf("main()\t\t\t\t%d threads created\n",num_threads);    /* wait until all threads have finished */  for (i = 0; i < num_threads; i++) {    pthread_join(threads[i], NULL);    printf("main()\t\tjoined to thread %d \n", i);  }    printf("main()\t\tall %d threads have finished. \n", num_threads);  return 0;}