/* * Test case for assertion #3 of the sigaction system call that shows * calling sigaction with a null act argument does not change the  * signal handler. * * Steps: * 1. Initialize global variable to indicate handler has not been called * 2. Set the signal handler for SIGUSR1 to handler * 3. Call sigaction with a null act * 4. raise SIGUSR1  * 5. Verify handler was called.*/#include <signal.h>#include "compat.h"#define NTASKS 1static pthread_t thread[NTASKS];int handler_called = 0;void handler(int signo){	handler_called = 1;}void * th_code (void *arg){	struct sigaction act;	struct sigaction oact;		act.sa_handler = handler;	act.sa_flags = 0;	sigemptyset(&act.sa_mask);	if (sigaction(SIGUSR1,  &act, 0) == -1) {		perror("Unexpected error while attempting to setup test "		       "pre-conditions");		return -1;	}		if (sigaction(SIGUSR1,  0, &oact) == -1) {		perror("Unexpected error while attempting to setup test "		       "pre-conditions");		return -1;	}	if (raise(SIGUSR1) == -1) {		perror("Unexpected error while attempting to setup test "		       "pre-conditions");		return -1;	}	if (handler_called) {		printf("Test PASSED\n");		return 0;	}	printf("Test FAILED\n");	return -1;	}int init_module(void){  int i;  for(i=0;i<NTASKS;i++)    pthread_create(&thread[i], NULL,th_code,(void *) i);  return 0;  }void cleanup_module(void){ int i;  for(i=0;i<NTASKS;i++)    pthread_delete_np(thread[i]);}