No, as I wrote, I would assume any use of CoreFoundation types are only used in platform specific code (dealing with UI, system events, etc.), which would be a

No, as I wrote, I would assume any use of CoreFoundation types are only used in platform specific code (dealing with UI, system events, etc.), which would be a minority of the code base, and entirely unique to the platform. Using CoreFoundation in such code is entirely sensible. Generalizing a sort for something like this would be a waste of time with no gains (as long as the functionality is used correctly, like not assuming a non-specified sort to be stable). However, for the actual business logic, the hierarchy would be: stdlib > large third-party cross-platform lib > small third party cross-platform lib ≈ homegrown implementation.