#include <stdlib.h>#include <stdio.h>#include <unistd.h>#include <sys/wait.h>#include <pthread.h> #undef waitpid#undef pipe#undef wait static int sigpid;static voidsigenable(int sig, int enabled){	sigset_t mask;	sigemptyset(&mask);	sigaddset(&mask, sig);	sigprocmask(enabled ? SIG_UNBLOCK : SIG_BLOCK, &mask, 0);} static voidchild(void){	int status, pid;printf("wait %d in %d\n", sigpid, getpid());	pid = waitpid(sigpid, &status, __WALL);	if(pid < 0)		perror("wait");	else if(WIFEXITED(status))		 _exit(WEXITSTATUS(status));printf("pid %d if %d %d\n", pid, WIFEXITED(status), WEXITSTATUS(status));	_exit(97);} static voidsigpass(int sig){	if(sig == SIGCHLD){print("sig\n");		child();	}else		kill(sigpid, sig);} void_threadsetupdaemonize(void){	int i, n, pid;	int p[2];	char buf[20]; 	sigpid = 1; 	if(pipe(p) < 0)		abort(); 	signal(SIGCHLD, sigpass);	switch(pid = fork()){	case -1:		abort();	default:		close(p[1]);		break;	case 0:		close(p[0]);		return;	} 	sigpid = pid; 	read(p[0], buf, sizeof buf-1);print("pipe\n");	child();} void*sleeper(void *v){	pthread_mutex_t m;	pthread_cond_t c; 	pthread_mutex_init(&m, 0);	pthread_cond_init(&c, 0);	pthread_cond_wait(&c, &m);	return 0;} voidmain(int argc, char **argv){	pthread_t pid; 	_threadsetupdaemonize();	pthread_create(&pid, 0, sleeper, 0);	exit(1);}