Errors when building OCCA transpiler with with LLVM, Clang built from source

[kris-rowe]

When trying to build the occa transpiler with the latest LLVM, Clang built from the llvm-project source I ran into several issues.

• The strict requirement for LLVM 17 needs to be relaxed here. I can check-out and build v17 if it is explicitly required, however we should document somewhere why it is required.
• Several C++ related compiler errors, e.g.

 /home/krowe/OCCA/occa/deps/occa-transpiler/lib/core/transpiler_session/header_info.h:49:73: 
   error: non-virtual member function marked 'override' hides virtual member function
   49 |                             clang::SrcMgr::CharacteristicKind FileType) override;

Has anyone on the occa transpiler development team successfully tested the transpiler with a from-source LLVM build? If they have could they share any relevant flags, etc. that should be used?

[YuraCobain]

Hi Kris,
Thank you for reporting.
We will go via triage procedure and give a comprehensive answer on Monday.

[kris-rowe]

@YuraCobain Awesome, thank you.

This scenario is relevant to large HPC systems where users likely don't have sudo privileges.

[YuraCobain]

Sure, we will add compatibility with clang version 17 and higher. Unfortunately clang community do not bother with compatibility of API between versions.

[YuraCobain]

Hi @kris-rowe,

The PR is updated with instructions how to build clang from source and how to configure OCCA to use it.
So far clang-17 is hard requirement and minimum version that consists all necessary features for a new transpiler.

Newer versions(18,19,20) of clang are not beneficial for transpiler.
To support them a compatibility layer should be added to transpiler as a feature because there is slight incompatibility in C++ API in clang tooling of newer versions.
I would appreciate any contribution from community to add compatibility layer.

[IuriiKobein]

Hi @kris-rowe
Do you have a chance to test the fix?