/*	Minimal defensive signal handling	AUP2, Sec. 9.01.8	Copyright 2003 by Marc J. Rochkind. All rights reserved.	May be copied only for purposes and under conditions described	on the Web page www.basepath.com/aup/copyright.htm.	The Example Files are provided "as is," without any warranty;	without even the implied warranty of merchantability or fitness	for a particular purpose. The author and his publisher are not	responsible for any damages, direct or incidental, resulting	from the use or non-use of these Example Files.	The Example Files may contain defects, and some contain deliberate	coding mistakes that were included for educational reasons.	You are responsible for determining if and how the Example Files	are to be used.*/#include "defs.h"/*[clean_up]*/static void clean_up(void){	/*		Clean-up code goes here --		must be async-signal-safe.	*/}static size_t strlen_safe(const char *s){	size_t n = 0;	while (*s++ != '\0')		n++;	return n;}/*[handler]*/static void handler(int signum){	int i;	struct {		int signum;		char *msg;	} sigmsg[] = {		{ SIGTERM, "Termination signal" },		{ SIGBUS, "Access to undefined portion of a memory object" },		{ SIGFPE, "Erroneous arithmetic operation" },		{ SIGILL, "Illegal instruction" },		{ SIGSEGV, "Invalid memory reference" },		{ SIGSYS, "Bad system call" },		{ SIGXCPU, "CPU-time limit exceeded" },		{ SIGXFSZ, "File-size limit exceeded" },		{ 0, NULL}	};	clean_up();	for (i = 0; sigmsg[i].signum > 0; i++)		if (sigmsg[i].signum == signum) {			(void)write(STDERR_FILENO, sigmsg[i].msg,			  strlen_safe(sigmsg[i].msg));			(void)write(STDERR_FILENO, "\n", 1);			break;		}	_exit(EXIT_FAILURE);}/*[handle_signals]*/static bool handle_signals(void){	sigset_t set;	struct sigaction act;	ec_neg1( sigfillset(&set) )	ec_neg1( sigprocmask(SIG_SETMASK, &set, NULL) )	memset(&act, 0, sizeof(act));	ec_neg1( sigfillset(&act.sa_mask) )	act.sa_handler = SIG_IGN;	ec_neg1( sigaction(SIGHUP, &act, NULL) )	ec_neg1( sigaction(SIGINT, &act, NULL) )	ec_neg1( sigaction(SIGQUIT, &act, NULL) )	ec_neg1( sigaction(SIGPIPE, &act, NULL) )	act.sa_handler = handler;	ec_neg1( sigaction(SIGTERM, &act, NULL) )	ec_neg1( sigaction(SIGBUS, &act, NULL) )	ec_neg1( sigaction(SIGFPE, &act, NULL) )	ec_neg1( sigaction(SIGILL, &act, NULL) )	ec_neg1( sigaction(SIGSEGV, &act, NULL) )	ec_neg1( sigaction(SIGSYS, &act, NULL) )	ec_neg1( sigaction(SIGXCPU, &act, NULL) )	ec_neg1( sigaction(SIGXFSZ, &act, NULL) )	ec_neg1( sigemptyset(&set) )	ec_neg1( sigprocmask(SIG_SETMASK, &set, NULL) )	return true;EC_CLEANUP_BGN	return false;EC_CLEANUP_END}/*[]*/void process(void){	ec_false (handle_signals() )	sleep(2);	exit(EXIT_SUCCESS);EC_CLEANUP_BGN	exit(EXIT_FAILURE);EC_CLEANUP_END}#define MAX_SIG 50int main(void){	sigset_t set;	int x = 1, y;	ec_neg1( sigfillset(&set) )	ec_neg1( sigprocmask(SIG_SETMASK, &set, NULL) )	y = x / 0;#if 0	int signum;	pid_t pid[MAX_SIG + 1];	int status;	for (signum = 1; signum <= MAX_SIG; signum++) {		ec_neg1( pid[signum] = fork() )		if (pid[signum] == 0)			process();		sleep(1);		printf("\nSending signal %d...\n", signum);		if (kill(pid[signum], signum) == -1)			printf("\tkill failed\n");		ec_neg1( waitpid(-1, &status, WUNTRACED) )		if (WIFEXITED(status))			printf("%ld exited normally\n", (long)pid[signum]);		else if (WIFSIGNALED(status))			printf("%ld exited with signal %d\n", (long)pid[signum],			  WTERMSIG(status));		else			printf("wait returned with other status\n");	}	for (signum = 1; signum <= MAX_SIG; signum++)		(void)kill(pid[signum], SIGKILL);#endif	exit(EXIT_SUCCESS);EC_CLEANUP_BGN	exit(EXIT_FAILURE);EC_CLEANUP_END}/*[]*/