aaron.ballman marked an inline comment as done. ================ Comment at: include/clang/Frontend/LangStandards.def:94 @@ -93,1 +93,3 @@ +// C2X modes +LANGSTANDARD(c2x, "c2x", ---------------- majnemer wrote: > Should this be C2x instead of C2X? Probably. :-D https://reviews.llvm.org/D23453