[C++20] [Modules] Missing features and problems

[ChuanqiXu9]

This is a summary issue to collect the missing features and problems for the support of modules. We only collect issues that have a wider impact and we have a good understanding for the internal reasons here. We hope we can say the support is done when we fixed all the issue in the list.

Missing spec features

• Lookup in module level
• Diagnose for exposure of TUlocal entity

ABI related

The bugs collected here need the guidance from Itanium C++ ABI group to progress. Otherwise, we (clang) will have the risk to have non-compatible ABI with Itanium C++ ABI. I think this is more harmful in the long term.

• linkage of lambda's initializer

[llvmbot]

@llvm/issue-subscribers-clang-modules

Author: Chuanqi Xu (ChuanqiXu9)

This is a summary issue to collect the missing features and problems for the support of modules. We only collect issues that have a wider impact and we have a good understanding for the internal reasons here. We hope we can say the support is done when we fixed all the issue in the list.

Missing spec features

#90154
#112294

ABI related

#110146