Log what is happening with window and session reference counts much more

obviously.

alerts.c

@@ -64,7 +64,7 @@ alerts_callback(__unused int fd, __unused short events, __unused void *arg)
 		TAILQ_REMOVE(&alerts_list, w, alerts_entry);
 
 		w->flags &= ~WINDOW_ALERTFLAGS;
-		window_remove_ref(w);
+		window_remove_ref(w, __func__);
 	}
 	alerts_fired = 0;
 }
@@ -148,7 +148,7 @@ alerts_queue(struct window *w, int flags)
 		if (!w->alerts_queued) {
 			w->alerts_queued = 1;
 			TAILQ_INSERT_TAIL(&alerts_list, w, alerts_entry);
-			w->references++;
+			window_add_ref(w, __func__);
 		}
 
 		if (!alerts_fired) {

notify.c

@@ -101,12 +101,12 @@ notify_callback(struct cmdq_item *item, void *data)
 	if (ne->client != NULL)
 		server_client_unref(ne->client);
 	if (ne->session != NULL)
-		session_unref(ne->session);
+		session_remove_ref(ne->session, __func__);
 	if (ne->window != NULL)
-		window_remove_ref(ne->window);
+		window_remove_ref(ne->window, __func__);
 
 	if (ne->fs.s != NULL)
-		session_unref(ne->fs.s);
+		session_remove_ref(ne->fs.s, __func__);
 
 	free((void *)ne->name);
 	free(ne);
@@ -136,13 +136,13 @@ notify_add(const char *name, struct cmd_find_state *fs, struct client *c,
 	if (c != NULL)
 		c->references++;
 	if (s != NULL)
-		s->references++;
+		session_add_ref(s, __func__);
 	if (w != NULL)
-		w->references++;
+		window_add_ref(w, __func__);
 
 	cmd_find_copy_state(&ne->fs, fs);
-	if (ne->fs.s != NULL)
-		ne->fs.s->references++; /* cmd_find_valid_state need session */
+	if (ne->fs.s != NULL) /* cmd_find_valid_state needs session */
+		session_add_ref(ne->fs.s, __func__);
 
 	new_item = cmdq_get_callback(notify_callback, ne);
 	cmdq_append(NULL, new_item);

session.c

@@ -189,13 +189,21 @@ session_create(const char *prefix, const char *name, int argc, char **argv,
 	return (s);
 }
 
+/* Add a reference to a session. */
+void
+session_add_ref(struct session *s, const char *from)
+{
+	s->references++;
+	log_debug("%s: %s %s, now %d", __func__, s->name, from, s->references);
+}
+
 /* Remove a reference from a session. */
 void
-session_unref(struct session *s)
+session_remove_ref(struct session *s, const char *from)
 {
-	log_debug("session %s has %d references", s->name, s->references);
-
 	s->references--;
+	log_debug("%s: %s %s, now %d", __func__, s->name, from, s->references);
+
 	if (s->references == 0)
 		event_once(-1, EV_TIMEOUT, session_free, s, NULL);
 }
@@ -248,7 +256,7 @@ session_destroy(struct session *s)
 
 	free((void *)s->cwd);
 
-	session_unref(s);
+	session_remove_ref(s, __func__);
 }
 
 /* Check a session name is valid: not empty and no colons or periods. */

tmux.h

@@ -2112,7 +2112,8 @@ struct window_pane *window_pane_find_down(struct window_pane *);
 struct window_pane *window_pane_find_left(struct window_pane *);
 struct window_pane *window_pane_find_right(struct window_pane *);
 void		 window_set_name(struct window *, const char *);
-void		 window_remove_ref(struct window *);
+void		 window_add_ref(struct window *, const char *);
+void		 window_remove_ref(struct window *, const char *);
 void		 winlink_clear_flags(struct winlink *);
 int		 winlink_shuffle_up(struct session *, struct winlink *);
 
@@ -2226,7 +2227,8 @@ struct session	*session_create(const char *, const char *, int, char **,
 		     const char *, const char *, struct environ *,
 		     struct termios *, int, u_int, u_int, char **);
 void		 session_destroy(struct session *);
-void		 session_unref(struct session *);
+void		 session_add_ref(struct session *, const char *);
+void		 session_remove_ref(struct session *, const char *);
 int		 session_check_name(const char *);
 void		 session_update_activity(struct session *, struct timeval *);
 struct session	*session_next_session(struct session *);

window-choose.c

@@ -225,10 +225,10 @@ static void
 window_choose_data_free(struct window_choose_data *wcd)
 {
 	server_client_unref(wcd->start_client);
-	session_unref(wcd->start_session);
+	session_remove_ref(wcd->start_session, __func__);
 
 	if (wcd->tree_session != NULL)
-		session_unref(wcd->tree_session);
+		session_remove_ref(wcd->tree_session, __func__);
 
 	free(wcd->ft_template);
 	format_free(wcd->ft);

window.c

@@ -186,11 +186,11 @@ winlink_set_window(struct winlink *wl, struct window *w)
 {
 	if (wl->window != NULL) {
 		TAILQ_REMOVE(&wl->window->winlinks, wl, wentry);
-		window_remove_ref(wl->window);
+		window_remove_ref(wl->window, __func__);
 	}
 	TAILQ_INSERT_TAIL(&w->winlinks, wl, wentry);
 	wl->window = w;
-	w->references++;
+	window_add_ref(w, __func__);
 }
 
 void
@@ -200,7 +200,7 @@ winlink_remove(struct winlinks *wwl, struct winlink *wl)
 
 	if (w != NULL) {
 		TAILQ_REMOVE(&w->winlinks, wl, wentry);
-		window_remove_ref(w);
+		window_remove_ref(w, __func__);
 	}
 
 	RB_REMOVE(winlinks, wwl, wl);
@@ -361,8 +361,7 @@ window_create_spawn(const char *name, int argc, char **argv, const char *path,
 static void
 window_destroy(struct window *w)
 {
-	if (!TAILQ_EMPTY(&w->winlinks))
-		fatalx("window destroyed with winlinks");
+	log_debug("window @%u destroyed (%d references)", w->id, w->references);
 
 	RB_REMOVE(windows, &windows, w);
 
@@ -387,11 +386,18 @@ window_destroy(struct window *w)
 }
 
 void
-window_remove_ref(struct window *w)
+window_add_ref(struct window *w, const char *from)
+{
+	w->references++;
+	log_debug("%s: @%u %s, now %d", __func__, w->id, from, w->references);
+}
+
+void
+window_remove_ref(struct window *w, const char *from)
 {
-	if (w->references == 0)
-		fatal("bad reference count");
 	w->references--;
+	log_debug("%s: @%u %s, now %d", __func__, w->id, from, w->references);
+
 	if (w->references == 0)
 		window_destroy(w);
 }