https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120527
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- Maybe we should default to the portable fallback but allow users (or packagers like macports) to select the faster impl at configure time if compat isn't needed. I'll have a quick look at what would be needed for a dynamic selection based on the presence of the weak symbols. I don't think it will be easy though. At the very least the code would get more complicated, but it might be useful on Linux too if it allowed easy testing of the non-futex paths by flipping a runtime toggle.
