[libcxx-commits] [PATCH] D92214: [libc++] Implement format_error.

Louis Dionne via Phabricator via libcxx-commits libcxx-commits at lists.llvm.org
Fri Jan 29 08:10:57 PST 2021

ldionne added a comment.

> I'd argue that compiling the library in C++17 and using it in C++20 (and using these C++20 features) is silly.

Yes, I agree.

> I imagine it would be to much of a pain to guarantee that it works the other way round (compiling in C++20, using in C++17), but it should work in most of the cases.

No, that's actually what we do all the time. We build the dylib in C++20, but users are free to use the headers in C++03, C++11, C++14, C++17 or C++20 mode.

@Mordante Feel free to add back the check. However, in the short/mid term, I want the default way to build libc++ to switch to the bootstrap build (i.e. the Runtimes build). Once that happens, we will be guaranteed that we always build the dylib with basically Clang trunk (or a recent compiler anyway). It won't make sense anymore to allow anything but the latest standard then. It is indeed a maintenance burden to support more than that, and a burden that (I claim) doesn't provide much benefit. If you're compiling the C++ Standard Library from scratch, I think you have the time and dedication to keep your compiler up to date.

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