LLVM Clang 9.0 Picks Up Initial C2x Language Mode

Merged today to the mainline Clang compiler front-end is the initial C2x language mode support as what will eventually be the successor to the C18 programming language.

C2x is still quite a ways out from release and its changes still under determination. At this stage the C2x language support for LLVM Clang is just enabling support by default for the [[attribute]] (double square brackets attribute; similar to C++) support.

But at least the initial plumbing is now in place for handling --std=c2x as the C2x changes build up.

This initial C2x placement is in what will be LLVM Clang 9.0 when released this autumn. On the GNU side, GCC 9 has the initial C2x bits.