This makes the code a bit simpler and (I think) removes the undefined behaviour from the normal string layout. Reviewed By: ldionne, Mordante, #libc Spies: labath, dblaikie, JDevlieghere, krytarowski, jgorbe, jingham, saugustine, arichardson, libcxx-commits Differential Revision: https://reviews.llvm.org/D123580