As I mentioned, and as the comment, "Provide the ability to override linkage features of the <b>interface</b>.", (bolding added), suggests, those PP symbols are an outward facing feature rather than merely an implementation detail. There is extremely low likelihood that they will change or vanish for that reason. We would not like to force those library users who rely on them to have to find another solution, or (heaven forbid) be forced to munge the sources.