With C++20 now being deemed complete from the recent ISO C++ meeting in Prague, the GNU Compiler Collection went ahead and added the -std=c++20 flag where as up until that change this weekend relied upon the -std=c++2a switch. LLVM’s Clang compiler now has similar treatment on its codebase…

Source: Phoronix – LLVM Clang 11 Adds -std=c++20 Support