[llvm-dev] Clang-12 fails build on MacOS

Fri Jul 16 13:58:30 PDT 2021

The error is basically:

:info:build CMake Error: failed to create symbolic link '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-12/clang-12/work/build/projects/compiler-rt/lib/builtins/outline_atomic_helpers.dir/outline_atomic_ldadd2_1.S': file already exists

Understood, thanks!

Looks like this is caused by https://reviews.llvm.org/D93178. It seems that when you build multiple arm64 slice (in this case, arm64 and arm64e), the LSE builtin will be generated twice. In the rare case that when two same `cmake -E create_symlink` running at the same time, you get that error. Before the change, it was compiling using clang so you don't get this weird race condition.

The problem is – even when I am forcing Macports to not build “fat” binaries (aka, limit the build to x86_64 only), I’m still getting an error.

You can probably workaround by manually set `DARWIN_osx_BUILTIN_ARCHS` to remove `arm64e` since you don't really need that. 

Please see above. I don’t think it helped – at least when I’m building via Macports (where what I’m doing should be the same or equivalent to what you’re suggesting). :-(

At the meantime, can you file a bug report to bugs.llvm.org?

I was told this reporting mechanism is going away…?

But sure, if you think it makes sense, I’ll file a report there.

Thanks!

On Jul 16, 2021, at 12:24 PM, Blumenthal, Uri - 0553 - MITLL via llvm-dev <llvm-dev at lists.llvm.org> wrote:

It seems there’s a problem with parallel builds, but I don’t really know the cause of the problem. You can see the screen log and the complete build log here: https://trac.macports.org/ticket/63026#comment:5

iMac Pro (Intel Core i9, 10 cores), MacOS Big Sur 11.4, Xcode-12.5.1, clang-12.0.1.

It would be great if this problem is resolved.

Thanks!

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Uri Blumenthal                              Voice: (781) 981-1638 

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