Instead of fixed size buffers for some messages, send only the string length.

client.c

@@ -488,33 +488,33 @@ client_write(int fd, const char *data, size_t size)
 
 /* Dispatch imsgs when in wait state (before MSG_READY). */
 int
-client_dispatch_wait(void *data)
+client_dispatch_wait(void *data0)
 {
 	struct imsg		 imsg;
+	char			*data;
 	ssize_t			 n, datalen;
-	struct msg_shell_data	shelldata;
-	struct msg_exit_data	exitdata;
 	struct msg_stdout_data	 stdoutdata;
 	struct msg_stderr_data	 stderrdata;
-	const char             *shellcmd = data;
+	int			 retval;
 
 	for (;;) {
 		if ((n = imsg_get(&client_ibuf, &imsg)) == -1)
 			fatalx("imsg_get failed");
 		if (n == 0)
 			return (0);
+
+		data = imsg.data;
 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;
 
 		log_debug("got %d from server", imsg.hdr.type);
 		switch (imsg.hdr.type) {
 		case MSG_EXIT:
 		case MSG_SHUTDOWN:
-			if (datalen != sizeof exitdata) {
-				if (datalen != 0)
+			if (datalen != sizeof retval && datalen != 0)
 				fatalx("bad MSG_EXIT size");
-			} else {
-				memcpy(&exitdata, imsg.data, sizeof exitdata);
-				client_exitval = exitdata.retcode;
+			if (datalen == sizeof retval) {
+				memcpy(&retval, data, sizeof retval);
+				client_exitval = retval;
 			}
 			imsg_free(&imsg);
 			return (-1);
@@ -534,15 +534,15 @@ client_dispatch_wait(void *data)
 			break;
 		case MSG_STDOUT:
 			if (datalen != sizeof stdoutdata)
-				fatalx("bad MSG_STDOUT");
-			memcpy(&stdoutdata, imsg.data, sizeof stdoutdata);
+				fatalx("bad MSG_STDOUT size");
+			memcpy(&stdoutdata, data, sizeof stdoutdata);
 
 			client_write(STDOUT_FILENO, stdoutdata.data, stdoutdata.size);
 			break;
 		case MSG_STDERR:
 			if (datalen != sizeof stderrdata)
-				fatalx("bad MSG_STDERR");
-			memcpy(&stderrdata, imsg.data, sizeof stderrdata);
+				fatalx("bad MSG_STDERR size");
+			memcpy(&stderrdata, data, sizeof stderrdata);
 
 			client_write(STDERR_FILENO, stderrdata.data, stderrdata.size);
 			break;
@@ -558,14 +558,11 @@ client_dispatch_wait(void *data)
 			imsg_free(&imsg);
 			return (-1);
 		case MSG_SHELL:
-			if (datalen != sizeof shelldata)
-				fatalx("bad MSG_SHELL size");
-			memcpy(&shelldata, imsg.data, sizeof shelldata);
-			shelldata.shell[(sizeof shelldata.shell) - 1] = '\0';
+			if (data[datalen - 1] != '\0')
+				fatalx("bad MSG_SHELL string");
 
 			clear_signals(0);
-
-			shell_exec(shelldata.shell, shellcmd);
+			shell_exec(data, data0);
 			/* NOTREACHED */
 		case MSG_DETACH:
 			client_write_server(MSG_EXITING, NULL, 0);
@@ -586,8 +583,8 @@ int
 client_dispatch_attached(void)
 {
 	struct imsg		 imsg;
-	struct msg_lock_data	lockdata;
 	struct sigaction	 sigact;
+	char			*data;
 	ssize_t			 n, datalen;
 
 	for (;;) {
@@ -595,6 +592,8 @@ client_dispatch_attached(void)
 			fatalx("imsg_get failed");
 		if (n == 0)
 			return (0);
+
+		data = imsg.data;
 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;
 
 		log_debug("got %d from server", imsg.hdr.type);
@@ -612,8 +611,7 @@ client_dispatch_attached(void)
 			client_write_server(MSG_EXITING, NULL, 0);
 			break;
 		case MSG_EXIT:
-			if (datalen != 0 &&
-			    datalen != sizeof (struct msg_exit_data))
+			if (datalen != 0 && datalen != sizeof (int))
 				fatalx("bad MSG_EXIT size");
 
 			client_write_server(MSG_EXITING, NULL, 0);
@@ -646,12 +644,10 @@ client_dispatch_attached(void)
 			kill(getpid(), SIGTSTP);
 			break;
 		case MSG_LOCK:
-			if (datalen != sizeof lockdata)
-				fatalx("bad MSG_LOCK size");
-			memcpy(&lockdata, imsg.data, sizeof lockdata);
+			if (data[datalen - 1] != '\0')
+				fatalx("bad MSG_LOCK string");
 
-			lockdata.cmd[(sizeof lockdata.cmd) - 1] = '\0';
-			system(lockdata.cmd);
+			system(data);
 			client_write_server(MSG_UNLOCK, NULL, 0);
 			break;
 		default:

server-client.c

@@ -695,8 +695,6 @@ server_client_repeat_timer(unused int fd, unused short events, void *data)
 void
 server_client_check_exit(struct client *c)
 {
-	struct msg_exit_data	exitdata;
-
 	if (!(c->flags & CLIENT_EXIT))
 		return;
 
@@ -707,9 +705,7 @@ server_client_check_exit(struct client *c)
 	if (EVBUFFER_LENGTH(c->stderr_data) != 0)
 		return;
 
-	exitdata.retcode = c->retval;
-	server_write_client(c, MSG_EXIT, &exitdata, sizeof exitdata);
-
+	server_write_client(c, MSG_EXIT, &c->retval, sizeof c->retval);
 	c->flags &= ~CLIENT_EXIT;
 }
 
@@ -995,16 +991,12 @@ server_client_msg_identify(
 void
 server_client_msg_shell(struct client *c)
 {
-	struct msg_shell_data	 data;
 	const char	*shell;
 
 	shell = options_get_string(&global_s_options, "default-shell");
-
 	if (*shell == '\0' || areshell(shell))
 		shell = _PATH_BSHELL;
-	if (strlcpy(data.shell, shell, sizeof data.shell) >= sizeof data.shell)
-		strlcpy(data.shell, _PATH_BSHELL, sizeof data.shell);
+	server_write_client(c, MSG_SHELL, shell, strlen(shell) + 1);
 
-	server_write_client(c, MSG_SHELL, &data, sizeof data);
 	c->flags |= CLIENT_BAD;	/* it will die after exec */
 }

server-fn.c

@@ -237,7 +237,6 @@ server_lock_client(struct client *c)
 {
 	const char	*cmd;
 	size_t		 cmdlen;
-	struct msg_lock_data	 lockdata;
 
 	if (c->flags & CLIENT_CONTROL)
 		return;
@@ -246,8 +245,7 @@ server_lock_client(struct client *c)
 		return;
 
 	cmd = options_get_string(&c->session->options, "lock-command");
-	cmdlen = strlcpy(lockdata.cmd, cmd, sizeof lockdata.cmd);
-	if (cmdlen >= sizeof lockdata.cmd)
+	if (strlen(cmd) + 1 > MAX_IMSGSIZE - IMSG_HEADER_SIZE)
 		return;
 
 	tty_stop_tty(&c->tty);
@@ -256,7 +254,7 @@ server_lock_client(struct client *c)
 	tty_raw(&c->tty, tty_term_string(c->tty.term, TTYC_E3));
 
 	c->flags |= CLIENT_SUSPENDED;
-	server_write_client(c, MSG_LOCK, &lockdata, sizeof lockdata);
+	server_write_client(c, MSG_LOCK, cmd, strlen(cmd) + 1);
 }
 
 void

tmux.h

@@ -487,22 +487,10 @@ struct msg_identify_data {
 	int		flags;
 };
 
-struct msg_lock_data {
-	char		cmd[COMMAND_LENGTH];
-};
-
 struct msg_environ_data {
 	char		var[ENVIRON_LENGTH];
 };
 
-struct msg_shell_data {
-	char		shell[MAXPATHLEN];
-};
-
-struct msg_exit_data {
-	int		retcode;
-};
-
 struct msg_stdin_data {
 	ssize_t	size;
 	char	data[BUFSIZ];