#include <u.h>#include <sys/wait.h>#include <signal.h>#include <libc.h>#undef rfork static voidnop(int x){	USED(x);} intp9rfork(int flags){	int pid, status;	int p[2];	int n;	char buf[128], *q;	extern char **environ; 	if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){		/* check other flags before we commit */		flags &= ~(RFPROC|RFFDG|RFENVG);		n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT|RFCENVG));		if(n){			werrstr("unknown flags %08ux in rfork", n);			return -1;		}		if(flags&RFNOWAIT){			/*			 * BUG - should put the signal handler back after we			 * finish, but I just don't care.  If a program calls with			 * NOWAIT once, they're not likely to want child notes			 * after that.			 */			signal(SIGCHLD, nop);			if(pipe(p) < 0)				return -1;		}		pid = fork();		if(pid == -1)			return -1;		if(flags&RFNOWAIT){			flags &= ~RFNOWAIT;			if(pid){				/*				 * Parent - wait for child to fork wait-free child.				 * Then read pid from pipe.  Assume pipe buffer can absorb the write.				 */				close(p[1]);				status = 0;				if(wait4(pid, &status, 0, 0) < 0){					werrstr("pipe dance - wait4 - %r");					close(p[0]);					return -1;				}				n = readn(p[0], buf, sizeof buf-1);				close(p[0]);				if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){					if(!WIFEXITED(status))						werrstr("pipe dance - !exited 0x%ux", status);					else if(WEXITSTATUS(status) != 0)						werrstr("pipe dance - non-zero status 0x%ux", status);					else if(n < 0)						werrstr("pipe dance - pipe read error - %r");					else if(n == 0)						werrstr("pipe dance - pipe read eof");					else						werrstr("pipe dance - unknown failure");					return -1;				}				buf[n] = 0;				if(buf[0] == 'x'){					werrstr("%s", buf+2);					return -1;				}				pid = strtol(buf, &q, 0);			}else{				/*				 * Child - fork a new child whose wait message can't 				 * get back to the parent because we're going to exit!				 */				signal(SIGCHLD, SIG_IGN);				close(p[0]);				pid = fork();				if(pid){					/* Child parent - send status over pipe and exit. */					if(pid > 0)						fprint(p[1], "%d", pid);					else						fprint(p[1], "x %r");					close(p[1]);					_exit(0);				}else{					/* Child child - close pipe. */					close(p[1]);				}			}		}		if(pid != 0)			return pid;		if(flags&RFCENVG)			if(environ)				*environ = nil;	}	if(flags&RFPROC){		werrstr("cannot use rfork for shared memory -- use libthread");		return -1;	}	if(flags&RFNAMEG){		/* XXX set $NAMESPACE to a new directory */		flags &= ~RFNAMEG;	}	if(flags&RFNOTEG){		setpgid(0, getpid());		flags &= ~RFNOTEG;	}	if(flags&RFNOWAIT){		werrstr("cannot use RFNOWAIT without RFPROC");		return -1;	}	if(flags){		werrstr("unknown flags %08ux in rfork", flags);		return -1;	}	return 0;}