On 12.11.22 14:32, Giuseppe D'Angelo via Development wrote: > I'm not sure if this has been explicitly discussed, but a prerequisite > for this scheme to work is that compiler vendors *do not* define library > feature macros inside <version> that you cannot use in the current C++ > version. In other words, having the proposed: > > #if __cpp_some_cpp23_feature > # include <cpp23_feature> > #endif > > is never going to blow up with some #error inside the included header > when compiling in pre-C++23 mode. I'm guessing that's always the case, > right?
I'm hoping that the vendors have learned from the SD-6 __has_include fiasco, and won't repeat it for C++23. So far, the CI results, as well as inspecting <version> in the three openly-visible implementations (MS STL, libc++, libstdc++) suggests that they did: - https://github.com/llvm/llvm-project/blob/main/libcxx/include/version#L381 - https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/std/version#L302 - https://github.com/microsoft/STL/blob/main/stl/inc/yvals_core.h#L1644 From my pov, the risk is currently more on the C++17 side. Thanks, Marc -- Marc Mutz <marc.m...@qt.io> Principal Software Engineer The Qt Company Erich-Thilo-Str. 10 12489 Berlin, Germany www.qt.io Geschäftsführer: Mika Pälsi, Juha Varelius, Jouni Lintunen Sitz der Gesellschaft: Berlin, Registergericht: Amtsgericht Charlottenburg, HRB 144331 B _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
