Upgrading clang on CI

[Ilmari Lauhakangas]

On 17.2.2025 22.15, Hossein Nourikhah wrote:
> Hello,
> 
> The baseline for LibreOffice C++ source code is now C++20. But, the 
> clang 12 installed on CI machines is quite old, and lacks some important 
> C++20 features. ("/home/tdf/lode/opt_private/clang-llvmorg-12.0.1/bin/ 
> clang" is visible in the build logs)
> 
> C++ ranges library is one example:
> https://en.cppreference.com/w/cpp/ranges/reverse_view
> 
> This is a related CI failure because of lacking C++ ranges library support:
> https://ci.libreoffice.org/job/gerrit_master_ml/35822/
> 
> More details about C++20 support from different compilers can be seen here:
> 
> C++20 library features
> https://en.cppreference.com/w/cpp/ 
> compiler_support#C.2B.2B20_library_features
> 
> Looking into the details of clang releases, I think clang versions until 
> and including 17 are no longer supported.
> https://llvm.org/docs/HowToReleaseLLVM.html
> 
> The current stable release is 19, an the preview release is 20.
> https://releases.llvm.org/
> 
> I am not sure about 18, but it is the version available in many Linux 
> distributions, and it seems to build LibreOffice from sources smoothly.
> 
> Ubuntu LTS: 20.04, 24.04, 22.04 (via llvm apt repository), RHEL 8 and 9 
> (via Clang and LLVM Toolset) and many other distributions:
> https://packages.ubuntu.com/search? 
> searchon=contents&keywords=clang&mode=exactfilename&suite=focal- 
> updates&arch=any
> https://packages.ubuntu.com/search? 
> searchon=contents&keywords=clang&mode=exactfilename&suite=noble- 
> updates&arch=any
> 
> Is it possible upgrade clang on CI machines to version 18 (or possibly, 
> 19)?

This is not a question about CI, but the whole Linux baseline and should 
be discussed in an ESC meeting.

Ilmari