On Mon, 20 Mar 2023 at 14:10, Ron Olson wrote:

Hey all-

I got this issue in my GH account I use for building Swift for Fedora: https://github.com/tachoknight/swift-lang-packaging-fedora/issues/2. The TL;DR is that the person was trying to build Swift on Rawhide which he moved to from an older version of Fedora. This tracks with something I discovered as well: I have a current Fedora VM (not Rawhide) that I’ve been upgrading from version to version for several years now, and suddenly it cannot build Swift due to a series of bizarre error messages like:

…
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/set:60:10: note: in file included from /usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/set:60:
#include <bits/stl_tree.h>
^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/stl_tree.h:2008:5: error: missing '#include "gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/stl_pair.h"'; 'pair' must be declared before it is used
pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
^
/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/bits/stl_pair.h:185:12: note: declaration here is not visible
struct pair
…

However, using mock or a container, it builds fine, Rawhide, F37, whatever.

I’m guessing there’s a setting or environment variable or … ?

No, I don't think so. There's no environment variable that is needed to stop the C++ standard library headers being completely broken.

The errors above and in the GH issue make no sense to me, maybe it's a bug in Clang's modules that allow a header to be reincluded, but I don't know why it only shows up on your VM and the reporter's system.