On Mon, 31 Jan 2022 at 22:45, Ron Olson <tachoknight@xxxxxxxxx> wrote: > > Hey all, > > I’m troubleshooting an issue and came up with this sample program: https://pastebin.com/g9S8Z64q to demonstrate the problem. Basically, clang 13, on Rawhide, won’t compile that program, while on Fedora 35 it does. > > The reason why is that on Rawhide, stdatomic.h exists under /usr/include/c++/12 while it does not exist on 35, so clang uses its built-in stdatomic per https://clang.llvm.org/docs/LanguageExtensions.html#c11-atomic-operations. But that's about C, not C++. >If it uses its internal version, the sample program compiles fine. > > Looking at stdatomic.h on Rawhide, I see it’s gated by “#if __cplusplus > 202002L”, so that means C++2b or later, not C++20. This seems to create a problem for clang which, since the file is present, wants to use it, but since it’s effectively empty due to the #ifdef, compiling of the sample program fails. > > Is it possible to disable clang’s use of the header file as a flag? I’ve been unable to find anything like that, and obviously renaming the header is out of the question. Also, is it correct to the setting stdatomic.h to only be used by c++2b? Yes, that's 100% correct. Clang is at fault here. <stdatomic.h> does not exist in C++ up to and including the current C++20 standard, so Clang should not assume it's present or usable. In C++23 there is now a <stdatomic.h> header in the C++ library for compatibility. That's what I added to GCC, and that's what Clang is now picking up. Why is C++ code in Clang using a C header that isn't part of C++? _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
