[libcxx-commits] [libcxx] [libc++][modules] Adds module testing. (PR #76246)

[Mark de Wever via libcxx-commits]

mordante wrote:

Interesting the first two errors are due to headers being available that are not available in libc++. Are the headers `<spanstream>` and `<stacktrace>` found from MSVC STL?

The `std::ctime` issue is due to the MSVC runtime not being a valid C runtime since some declarations have internal linkage. (The MSVC STL team is aware of this and MSVC STL is not the only runtime with this issue.) Using internal linkage is often benign, but it can't be used in modules.

Unfortunately I don't have access to Windows so I can't reproduce this issue. I think the following change would solve the issue https://github.com/llvm/llvm-project/blob/main/libcxx/utils/libcxx/test/features.py#L326
```
         when=lambda cfg: "__ANDROID__" in compilerMacros(cfg)                      
 +       or "_LIBCPP_ABI_VCRUNTIME" in compilerMacros(cfg)                          
         or "__PICOLIBC__" in compilerMacros(cfg) 
```
Can you test this fix?

https://github.com/llvm/llvm-project/pull/76246