do not call any functions before check errno

src/exec.c

@@ -110,7 +110,6 @@ static int pts_loop(struct hyper_event *de, uint64_t seq, int efd, struct hyper_
 
 	do {
 		size = read(de->fd, buf->data + buf->get + 12, buf->size - buf->get - 12);
-		fprintf(stdout, "%s: read %d data\n", __func__, size);
 		if (size < 0) {
 			if (errno == EINTR)
 				continue;
@@ -122,6 +121,8 @@ static int pts_loop(struct hyper_event *de, uint64_t seq, int efd, struct hyper_
 
 			break;
 		}
+		fprintf(stdout, "%s: read %d data\n", __func__, size);
+
 		if (size == 0) { // eof
 			pts_hup(de, efd, exec);
 			return 0;
@@ -544,13 +545,14 @@ static void hyper_exec_process(struct hyper_exec *exec, struct stdio_config *io)
 	}
 
 	if (execvp(exec->argv[0], exec->argv) < 0) {
+		// perror possibly changes the errno.
+		int err = errno;
 		perror("exec failed");
-
 		 /* the exit codes follow the `chroot` standard,
 		    see docker/docs/reference/run.md#exit-status */
-		if (errno == ENOENT)
+		if (err == ENOENT)
 			_exit(127);
-		else if (errno == EACCES)
+		else if (err == EACCES)
 			_exit(126);
 	}
 

src/init.c

@@ -1244,14 +1244,14 @@ static int hyper_loop(void)
 
 	while (1) {
 		n = epoll_pwait(ctl.efd, events, MAXEVENTS, -1, &omask);
-		fprintf(stdout, "%s epoll_wait %d\n", __func__, n);
-
 		if (n < 0) {
 			if (errno == EINTR)
 				continue;
 			perror("hyper wait event failed");
 			return -1;
 		}
+		fprintf(stdout, "%s epoll_wait %d\n", __func__, n);
+
 		for (i = 0; i < n; i++) {
 			if (hyper_handle_event(ctl.efd, &events[i]) < 0)
 				return -1;

src/net.c

@@ -48,7 +48,6 @@ int hyper_send_data(int fd, uint8_t *data, uint32_t len)
 
 	while (length < len) {
 		size = write(fd, data + length, len - length);
-
 		if (size <= 0) {
 			if (errno == EINTR)
 				continue;
@@ -99,7 +98,6 @@ int hyper_get_type(int fd, uint32_t *type)
 
 	while (len < 8) {
 		size = read(fd, buf + len, 8 - len);
-
 		if (size <= 0) {
 			if (errno == EINTR)
 				continue;

src/util.c

@@ -415,13 +415,12 @@ int hyper_open_channel(char *channel, int mode)
 {
 	struct termios term;
 	int fd = open(channel, O_RDWR | O_CLOEXEC | mode);
-	fprintf(stdout, "open %s get %d\n", channel, fd);
-
 	if (fd < 0) {
 		perror("fail to open channel device");
 		return -1;
 	}
 
+	fprintf(stdout, "open %s get %d\n", channel, fd);
 	bzero(&term, sizeof(term));
 
 	cfmakeraw(&term);