> Why would a stack frame want to move ownership to its callee
Happens all the time in modern programming:
callee(foo_string + "abc")
Argument expression foo_string + "abc" constructs a new string. That is not captured in any variable here; it is passed to the caller. Only the caller knows about this.
This situation can expose bugs in a run-time's GC system. If callee is something written in a low level language that is resposible for indicating "nailed" objects to the garbage collector, and it forgets to nail the argument object, GC can prematurely collect it because nothing else in the image knows about that object: only the callee. The bug won't surface in situations like callee(foo_string) where the caller still has a reference to foo_string (at least if that variable is live: has a next use).
Happens all the time in modern programming:
callee(foo_string + "abc")
Argument expression foo_string + "abc" constructs a new string. That is not captured in any variable here; it is passed to the caller. Only the caller knows about this.
This situation can expose bugs in a run-time's GC system. If callee is something written in a low level language that is resposible for indicating "nailed" objects to the garbage collector, and it forgets to nail the argument object, GC can prematurely collect it because nothing else in the image knows about that object: only the callee. The bug won't surface in situations like callee(foo_string) where the caller still has a reference to foo_string (at least if that variable is live: has a next use).