Ah, as I said - on latest main branch [g_once_init_enter](https://gitlab.gnome.org/GNOME/glib/-/blob/main/glib/gthread.c#L699) still has arg qualified by `volatile` qualifier right after asking not to use `volatile`.
The `volatile` qualifier has been there on the function prototype since the very beginning of `g_once_init_enter` (as per git blame 2007) and has never been removed.
And I don't see a warning on this PR with clang version 12.0.0-3ubuntu1~21.04.2.