Some interesting discoveries while trying to use Clang.jl

[hammerfunctor]

When I try to install Clang.jl for the first time, precompile doesn't work.
This error persist when I update to master branch.

(@v1.6) pkg> gc --all
      Active manifest files: 2 found
      Active artifact files: 71 found
      Active scratchspaces: 4 found
     Deleted 3 package installations (941.784 KiB)
     Deleted 2 repos (2.588 MiB)
     Deleted 1 artifact installation (404.595 MiB)

(@v1.6) pkg> add Clang
   Resolving package versions...
   Installed Clang ───── v0.13.0
   Installed Clang_jll ─ v11.0.1+3
   Installed CEnum ───── v0.4.1
  Downloaded artifact: Clang
    Updating `~/.julia/environments/v1.6/Project.toml`
  [40e3b903] + Clang v0.13.0
    Updating `~/.julia/environments/v1.6/Manifest.toml`
  [fa961155] + CEnum v0.4.1
  [40e3b903] + Clang v0.13.0
  [0ee61d77] + Clang_jll v11.0.1+3
  [8f36deef] + libLLVM_jll
Precompiling project...
  ✗ Clang
  2 dependencies successfully precompiled in 3 seconds (150 already precompiled)
  1 dependency errored. To see a full report either run `import Pkg; Pkg.precompile()` or load the package

(@v1.6) pkg> precompile
Precompiling project...
  ✗ Clang
  0 dependencies successfully precompiled in 3 seconds (152 already precompiled)

ERROR: The following 1 direct dependency failed to precompile:

Clang [40e3b903-d033-50b4-a0cc-940c62c95e31]

Failed to precompile Clang [40e3b903-d033-50b4-a0cc-940c62c95e31] to /home/huzf/.julia/compiled/v1.6/Clang/jl_pXpIWG.
ERROR: LoadError: could not load library "/home/huzf/.julia/artifacts/88dab3027140e5f49b87c98cdf19f51a90e85c85/lib/libclang.so"
libLLVM-11jl.so: cannot open shared object file: No such file or directory
Stacktrace:
 [1] clang_getClangVersion
   @ ~/.julia/packages/Clang/VVQij/gen/libclang_api.jl:1383 [inlined]
 [2] version()
   @ Clang ~/.julia/packages/Clang/VVQij/src/Clang.jl:68
 [3] top-level scope
   @ ~/.julia/packages/Clang/VVQij/src/Clang.jl:75
 [4] top-level scope (repeats 2 times)
   @ none:1
in expression starting at /home/huzf/.julia/packages/Clang/VVQij/src/Clang.jl:1

julia> versioninfo()
Julia Version 1.6.2
Commit 1b93d53fc4* (2021-07-14 15:36 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: AMD Ryzen 5 5600U with Radeon Graphics
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, znver3)

Next I suspect they change to llvm12 at v"1.6.2"? That's a bit of unreasonable.Release notes of v"1.6.2" then tell me no big changes happen here.

The last line reminds me that I download this package from the repository of ArchLinux. Under /usr/lib there also truly sits some llvm12 library, which is installed by the ArchLinux package llvm-libs.

$ l /usr/lib/libLLVM*     
lrwxrwxrwx root root 13 B  Wed Sep  8 08:26:45 2021  /usr/lib/libLLVM-12.0.1.so ⇒ libLLVM-12.so
.rwxr-xr-x root root 98 MB Wed Sep  8 08:26:45 2021  /usr/lib/libLLVM-12.so
lrwxrwxrwx root root 13 B  Wed Sep  8 08:26:45 2021  /usr/lib/libLLVM.so ⇒ libLLVM-12.so
$ yay -Ss llvm | grep Installed
multilib/lib32-llvm-libs 12.0.1-2 (27.3 MiB 106.9 MiB) (Installed)
extra/llvm-libs 12.0.1-4 (24.4 MiB 98.4 MiB) (Installed)
extra/lld 12.0.1-1 (2.9 MiB 22.4 MiB) (Installed)
extra/clang 12.0.1-1 (35.2 MiB 171.5 MiB) (Installed)

Finally I rush into julialang.org and download a newest image.

julia> versioninfo() # downloaded from julialang.org
Julia Version 1.6.2
Commit 1b93d53fc4 (2021-07-14 15:36 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: AMD Ryzen 5 5600U with Radeon Graphics
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-11.0.1 (ORCJIT, generic)

🤣So ArchLinux community really do some off-duty work.

[Gnimuc]

🤣So ArchLinux community really do some off-duty work.

This is mind-blowing. Did they backport those LLVM patches manually to make Julia 1.6 work with LLVM 12?

[hammerfunctor]

roflSo ArchLinux community really do some off-duty work.

This is mind-blowing. Did they backport those LLVM patches manually to make Julia 1.6 work with LLVM 12?

I have no idea, but so far everything works well except for Clang.jl.

[Gnimuc]

A workaround might be to change the LLVM version in this line to match the one used in the Julia of ArchLinux.

[hammerfunctor]

I'll give it a shoot. Or just to switch to AUR package julia-bin, which is download from julialang.org.
By the way, Arch style is really unruly🤣.