Instead of bailing out on the first configuration file error, carry on,

collecting all the errors, then start with the active window in more mode
displaying them.

cfg.c

@@ -34,6 +34,9 @@ void printflike2 cfg_print(struct cmd_ctx *, const char *, ...);
 void printflike2 cfg_error(struct cmd_ctx *, const char *, ...);
 
 char	 *cfg_cause;
+int       cfg_finished;
+char    **cfg_causes;
+u_int     cfg_ncauses;
 
 /* ARGSUSED */
 void printflike2
@@ -52,19 +55,38 @@ cfg_error(unused struct cmd_ctx *ctx, const char *fmt, ...)
 	va_end(ap);
 }
 
+void printflike3
+cfg_add_cause(u_int *ncauses, char ***causes, const char *fmt, ...)
+{
+	char	*cause;
+	va_list	 ap;
+
+	va_start(ap, fmt);
+	xvasprintf(&cause, fmt, ap);
+	va_end(ap);
+
+	*causes = xrealloc(*causes, *ncauses + 1, sizeof **causes);
+	(*causes)[(*ncauses)++] = cause;
+}
+
+/*
+ * Load configuration file. Returns -1 for an error with a list of messages in
+ * causes. Note that causes and ncauses must be initialised by the caller!
+ */
 int
-load_cfg(const char *path, struct cmd_ctx *ctxin, char **cause)
+load_cfg(
+    const char *path, struct cmd_ctx *ctxin, u_int *ncauses, char ***causes)
 {
 	FILE		*f;
 	u_int		 n;
-	char		*buf, *line, *ptr;
+	char		*buf, *line, *cause;
 	size_t		 len;
 	struct cmd_list	*cmdlist;
 	struct cmd_ctx	 ctx;
 
 	if ((f = fopen(path, "rb")) == NULL) {
-		xasprintf(cause, "%s: %s", path, strerror(errno));
-		return (1);
+		cfg_add_cause(ncauses, causes, "%s: %s", path, strerror(errno));
+		return (-1);
 	}
 	n = 0;
 
@@ -80,10 +102,13 @@ load_cfg(const char *path, struct cmd_ctx *ctxin, char **cause)
 		}
 		n++;
 
-		if (cmd_string_parse(buf, &cmdlist, cause) != 0) {
-			if (*cause == NULL)
+		if (cmd_string_parse(buf, &cmdlist, &cause) != 0) {
+			if (cause == NULL)
+				continue;
+			cfg_add_cause(
+			    ncauses, causes, "%s: %u: %s", path, n, cause);
+			xfree(cause);
 			continue;
-			goto error;
 		}
 		if (cmdlist == NULL)
 			continue;
@@ -107,23 +132,17 @@ load_cfg(const char *path, struct cmd_ctx *ctxin, char **cause)
 		cmd_list_exec(cmdlist, &ctx);
 		cmd_list_free(cmdlist);
 		if (cfg_cause != NULL) {
-			*cause = cfg_cause;
-			goto error;
+			cfg_add_cause(
+			    ncauses, causes, "%s: %d: %s", path, n, cfg_cause);
+			xfree(cfg_cause);
+			continue;
 		}
 	}
 	if (line != NULL)
 		xfree(line);
 	fclose(f);
 
+	if (*ncauses != 0)
+		return (-1);
 	return (0);
-
-error:
-	if (line != NULL)
-		xfree(line);
-	fclose(f);
-
-	xasprintf(&ptr, "%s: %s at line %u", path, *cause, n);
-	xfree(*cause);
-	*cause = ptr;
-	return (1);
 }

cmd-new-session.c

@@ -122,12 +122,13 @@ cmd_new_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct cmd_new_session_data	*data = self->data;
 	struct session			*s, *groupwith;
 	struct window			*w;
+	struct window_pane		*wp;
 	struct environ			 env;
 	struct termios			 tio, *tiop;
 	const char			*update;
 	char				*overrides, *cmd, *cwd, *cause;
 	int				 detached, idx;
-	u_int				 sx, sy;
+	u_int				 sx, sy, i;
 
 	if (data->newname != NULL && session_find(data->newname) != NULL) {
 		ctx->error(ctx, "duplicate session: %s", data->newname);
@@ -280,6 +281,21 @@ cmd_new_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 	recalculate_sizes();
 	server_update_socket();
 
+	/*
+	 * If there are still configuration file errors to display, put the new
+	 * session's current window into more mode and display them now.
+	 */
+	if (cfg_finished && cfg_ncauses != 0) {
+		wp = s->curw->window->active;
+		window_pane_set_mode(wp, &window_more_mode);
+		for (i = 0; i < cfg_ncauses; i++) {
+			window_more_add(wp, "%s", cfg_causes[i]);
+			xfree(cfg_causes[i]);
+		}
+		xfree(cfg_causes);
+		cfg_ncauses = 0;
+	}
+
 	return (!detached);	/* 1 means don't tell command client to exit */
 }
 

cmd-source-file.c

@@ -89,12 +89,18 @@ int
 cmd_source_file_exec(struct cmd *self, struct cmd_ctx *ctx)
 {
 	struct cmd_source_file_data	*data = self->data;
-	char				*cause;
+	char			       **causes;
+	u_int				 i, ncauses;
 
-	if (load_cfg(data->path, ctx, &cause) != 0) {
-		ctx->error(ctx, "%s", cause);
-		xfree(cause);
-		return (-1);
+	causes = NULL;
+	ncauses = 0;
+
+	if (load_cfg(data->path, ctx, &ncauses, &causes) != 0) {
+		for (i = 0; i < ncauses; i++) {
+			ctx->print(ctx, "%s", causes[i]);
+			xfree(causes[i]);
+		}
+		xfree(causes);
 	}
 
 	return (0);

server.c

@@ -113,10 +113,11 @@ server_create_socket(void)
 int
 server_start(char *path)
 {
-	struct client	*c;
-	int		 pair[2];
-	char		*cause, rpathbuf[MAXPATHLEN];
+	struct window_pane	*wp;
+	int	 		 pair[2], retval;
+	char			 rpathbuf[MAXPATHLEN];
 	struct timeval		 tv;
+	u_int			 i;
 
 	/* The first client is special and gets a socketpair; create it. */
 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pair) != 0)
@@ -166,15 +167,31 @@ server_start(char *path)
 	server_fd = server_create_socket();
 	server_client_create(pair[1]);
 
-	if (access(SYSTEM_CFG, R_OK) == 0) {
-		if (load_cfg(SYSTEM_CFG, NULL, &cause) != 0)
-			goto error;
-	} else if (errno != ENOENT) {
-		xasprintf(&cause, "%s: %s", strerror(errno), SYSTEM_CFG);
-		goto error;
+	retval = 0;
+	if (access(SYSTEM_CFG, R_OK) == 0)
+		load_cfg(SYSTEM_CFG, NULL, &cfg_ncauses, &cfg_causes);
+	else if (errno != ENOENT) {
+		cfg_add_cause(&cfg_ncauses, &cfg_causes,
+		    "%s: %s", strerror(errno), SYSTEM_CFG);
 	}
-	if (cfg_file != NULL && load_cfg(cfg_file, NULL, &cause) != 0)
-		goto error;
+	if (cfg_file != NULL)
+		load_cfg(cfg_file, NULL, &cfg_ncauses, &cfg_causes);
+
+	/*
+	 * If there is a session already, put the current window and pane into
+	 * more mode.
+	 */
+	if (!ARRAY_EMPTY(&sessions) && cfg_ncauses != 0) {
+		wp = ARRAY_FIRST(&sessions)->curw->window->active;
+		window_pane_set_mode(wp, &window_more_mode);
+		for (i = 0; i < cfg_ncauses; i++) {
+			window_more_add(wp, "%s", cfg_causes[i]);
+			xfree(cfg_causes[i]);
+		}
+		xfree(cfg_causes);
+		cfg_ncauses = 0;
+	}
+	cfg_finished = 1;
 
 	event_set(&server_ev_accept,
 	    server_fd, EV_READ|EV_PERSIST, server_accept_callback, NULL);
@@ -188,20 +205,6 @@ server_start(char *path)
 	server_signal_set();
 	server_loop();
 	exit(0);
-
-error:
-	/* Write the error and shutdown the server. */
-	c = ARRAY_FIRST(&clients);
-
-	server_write_error(c, cause);
-	server_write_client(c, MSG_EXIT, NULL, 0);
-	xfree(cause);
-
-	server_shutdown = 1;
-
-	server_signal_set();
-	server_loop();
-	exit(1);
 }
 
 /* Main server loop. */

tmux.c

@@ -432,15 +432,10 @@ main(int argc, char **argv)
 				home = pw->pw_dir;
 		}
 		xasprintf(&cfg_file, "%s/%s", home, DEFAULT_CFG);
-		if (access(cfg_file, R_OK) != 0) {
+		if (access(cfg_file, R_OK) != 0 && errno == ENOENT) {
 			xfree(cfg_file);
 			cfg_file = NULL;
 		}
-	} else {
-		if (access(cfg_file, R_OK) != 0) {
-			log_warn("%s", cfg_file);
-			exit(1);
-		}
 	}
 
 	/*

tmux.h

@@ -1257,7 +1257,11 @@ int		 checkshell(const char *);
 int		 areshell(const char *);
 
 /* cfg.c */
-int		 load_cfg(const char *, struct cmd_ctx *, char **);
+extern int       cfg_finished;
+extern char    **cfg_causes;
+extern u_int     cfg_ncauses;
+void printflike3 cfg_add_cause(u_int *, char ***, const char *, ...);
+int		 load_cfg(const char *, struct cmd_ctx *, u_int *, char ***);
 
 /* mode-key.c */
 extern const struct mode_key_table mode_key_tables[];
@@ -1867,6 +1871,7 @@ void		 window_copy_pageup(struct window_pane *);
 
 /* window-more.c */
 extern const struct window_mode window_more_mode;
+void		 window_more_add(struct window_pane *, const char *, ...);
 void		 window_more_vadd(struct window_pane *, const char *, va_list);
 
 /* window-choose.c */

window-more.c

@@ -52,6 +52,16 @@ struct window_more_mode_data {
 	u_int			top;
 };
 
+void
+window_more_add(struct window_pane *wp, const char *fmt, ...)
+{
+	va_list	ap;
+
+	va_start(ap, fmt);
+	window_more_vadd(wp, fmt, ap);
+	va_end(ap);
+}
+
 void
 window_more_vadd(struct window_pane *wp, const char *fmt, va_list ap)
 {

window.c

@@ -657,9 +657,6 @@ window_pane_parse(struct window_pane *wp)
 	char   *data;
 	size_t	new_size;
 
-	if (wp->mode != NULL)
-		return;
-
 	new_size = EVBUFFER_LENGTH(wp->event->input) - wp->pipe_off;
 	if (wp->pipe_fd != -1 && new_size > 0) {
 		data = EVBUFFER_DATA(wp->event->input);