swaybar: ensure correct init order for status_line

`$WAYLAND_SOCKET` is unset by `wl_display_connect` after it has
successfully connected to the wayland socket.

However, subprocesses spawned by swaybar (status-command) don't have
access to waybar's fds as $WAYLAND_SOCKET is O_CLOEXEC. This means any
status command which itself tries to connect to wayland will fail if
this environment variable is set.

Reorder display and status-command initialization so that this variable
is not set and add an assert so we can enforce this invariant in future.

1 files changed, 3 insertions, 0 deletions

diff --git a/swaybar/status_line.c b/swaybar/status_line.c
index fb9271f8..71ceb1d0 100644
--- a/swaybar/status_line.c
+++ b/swaybar/status_line.c
@@ -1,4 +1,5 @@
 #define _POSIX_C_SOURCE 200809L
+#include <assert.h>
 #include <fcntl.h>
 #include <sys/ioctl.h>
 #include <json.h>
@@ -153,6 +154,8 @@ struct status_line *status_line_init(char *cmd) {
                 exit(1);
         }
 
+        assert(!getenv("WAYLAND_SOCKET") && "display must be initialized before "
+                " starting `status-command`; WAYLAND_SOCKET should not be set");
         status->pid = fork();
         if (status->pid == 0) {
                 dup2(pipe_read_fd[1], STDOUT_FILENO);