As discussed in glib#600 (closed), the volatile qualifier rarely has the semantics that are desired in C/C++. With recent gcc versions, combining pointers to volatile-qualified types with the __atomic_foo() family of builtins causes compiler warnings.
http://c.isvolatileusefulwiththreads.com/ has some other useful references.
This fixes some (all?) of the CI failures seen on !41 and !43.