libposix: introduce pause() (still to be integrated in newlib)

qa/lib/newlib/030-pause.c

@@ -0,0 +1,67 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/wait.h>
+
+
+void sighup() {
+	signal(SIGHUP,sighup); /* reset signal */
+	printf("CHILD: SIGHUP received\n");
+}
+
+int
+main(int argc, char *argv[])
+{
+	pid_t cpid, w;
+	int ret, status;
+
+
+	cpid = fork();
+	if(cpid == -1){
+		perror("fork");
+		exit(EXIT_FAILURE);
+	}
+
+	if (cpid == 0) {	/* Code executed by child */
+		signal(SIGHUP, sighup); /* set function calls */
+
+		printf("Child PID is %ld, calling pause()...\n", (long) getpid());
+		ret = pause();
+
+		if(ret == -1 && errno == EINTR){
+			printf("Pause returned %d with errno = EINTR\n", ret);
+			_exit(0);
+		}
+		if(ret != -1)
+			printf("Pause returned %d\n", ret);
+		if(errno != EINTR)
+			printf("Pause returned but errno != EINTR\n");
+		_exit(1);
+	}
+
+	/* Code executed by parent */
+	sleep(5);
+	kill(cpid, SIGHUP);
+
+	do {
+		w = waitpid(cpid, &status, WUNTRACED);
+		if (w == -1) {
+			perror("waitpid");
+			exit(EXIT_FAILURE);
+		}
+
+		if (WIFEXITED(status)) {
+			printf("exited, status=%d\n", WEXITSTATUS(status));
+		} else if (WIFSIGNALED(status)) {
+			printf("killed by signal %d\n", WTERMSIG(status));
+			exit(EXIT_FAILURE);
+		} else if (WIFSTOPPED(status)) {
+			printf("stopped by signal %d\n", WSTOPSIG(status));
+			exit(EXIT_FAILURE);
+		}
+	} while (!WIFEXITED(status) && !WIFSIGNALED(status));
+	exit(EXIT_SUCCESS);
+
+}

qa/lib/newlib/build.json

@@ -34,6 +34,7 @@
 			"000-hello.c",
 			"010-fork.c",
 			"020-waitpid.c",
+			"030-pause.c",
 			"100-files.c",
 			"101-files.c",
 			"200-signals.c",

sys/src/lib/posix/others.c

@@ -60,6 +60,13 @@ POSIX_usleep(int *errnop, unsigned int usec)
 	return 0;
 }
 
+int
+POSIX_pause(int *errnop)
+{
+	rendezvous((void*)~0, 1);
+	*errnop = __libposix_get_errno(PosixEINTR);
+	return -1;
+}
 
 clock_t
 POSIX_times(int *errnop, void *buf)