misc: xcb_connect() always returns a non-NULL pointer

Instead, we need to check if xcb_connection_has_error() says something
went wrong. We also need to call xcb_disconnect() on the disfunctional
XCB connection object.

bar.c

@@ -324,8 +324,13 @@ run(struct bar *_bar)
     /* TODO: a lot of this (up to mapping the window) could be done in bar_new() */
     xcb_generic_error_t *e;
 
-    bar->conn = xcb_connect(NULL, NULL);
+    int default_screen;
-    assert(bar->conn != NULL);
+    bar->conn = xcb_connect(NULL, &default_screen);
+    if (xcb_connection_has_error(bar->conn) > 0) {
+        LOG_ERR("failed to connect to X");
+        xcb_disconnect(bar->conn);
+        return 1;
+    }
 
     const xcb_setup_t *setup = xcb_get_setup(bar->conn);
 

main.c

@@ -119,6 +119,15 @@ main(int argc, const char *const *argv)
         return 1;
     }
 
+    /* Connect to XCB, to be able to detect a disconnect (allowing us
+     * to exit) */
+    xcb_connection_t *xcb = xcb_connect(NULL, NULL);
+    if (xcb_connection_has_error(xcb) > 0) {
+        LOG_ERR("failed to connect to X");
+        xcb_disconnect(xcb);
+        return 1;
+    }
+
     xcb_init();
 
     bar->abort_fd = abort_fd;
@@ -129,11 +138,6 @@ main(int argc, const char *const *argv)
     /* Now unblock. We should be only thread receiving SIGINT */
     pthread_sigmask(SIG_UNBLOCK, &signal_mask, NULL);
 
-    /* Connect to XCB, to be able to detect a disconnect (allowing us
-     * to exit) */
-    xcb_connection_t *xcb = xcb_connect(NULL, NULL);
-    assert(xcb != NULL);
-
     /* Wait for SIGINT, or XCB disconnect */
     while (!aborted) {
         struct pollfd fds[] = {

modules/i3.c

@@ -376,7 +376,13 @@ run(struct module *mod)
 
     struct sockaddr_un addr = {.sun_family = AF_UNIX};
     {
-        xcb_connection_t *conn = xcb_connect(NULL, NULL);
+        int default_screen;
+        xcb_connection_t *conn = xcb_connect(NULL, &default_screen);
+        if (xcb_connection_has_error(conn) > 0) {
+            LOG_ERR("failed to connect to X");
+            xcb_disconnect(conn);
+            return 1;
+        }
 
         const xcb_setup_t *setup = xcb_get_setup(conn);
         xcb_screen_t *screen = xcb_setup_roots_iterator(setup).data;

modules/xwindow.c

@@ -196,9 +196,11 @@ run(struct module *mod)
 {
     struct private *m = mod->private;
 
-    m->conn = xcb_connect(NULL, NULL);
+    int default_screen;
-    if (m->conn == NULL) {
+    m->conn = xcb_connect(NULL, &default_screen);
+    if (xcb_connection_has_error(m->conn) > 0) {
         LOG_ERR("failed to connect to X");
+        xcb_disconnect(m->conn);
         return 1;
     }
 

xcb.c

@@ -48,8 +48,9 @@ bool
 xcb_init(void)
 {
     xcb_connection_t *conn = xcb_connect(NULL, NULL);
-    if (conn == NULL) {
+    if (xcb_connection_has_error(conn) > 0) {
         LOG_ERR("failed to connect to X");
+        xcb_disconnect(conn);
         return false;
     }