[libcxx-commits] [libcxx] [libcxx][clang-modules] Fix headers being marked as textual (PR #130723)

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matts1 wrote:

> Could you provide a reproducer for this issue? How do you come across it?

I'm on the chrome build team, and we're trying resolve #127012. We want to build libc++ into .pcm files, but this is currently not possible. We have a ([build file](https://source.chromium.org/chromium/chromium/src/+/main:buildtools/third_party/libc++/BUILD.gn;l=144-263;drc=9169de248fc0782050be0aec43372d77156dcf62)).

The reason this is not occuring in the modules CI builder is because the modules CI builder doesn't do this (I don't know what it does, but I know it's currently unsupported).

> All in all, it seems like the net effect of making this change is that we don't export the `__config_site` macros out of libc++ anymore. Perhaps there's a simple fix, but I tried a couple of things locally with no success.

That's correct. I believe I've now fixed it though.

> I don't have a problem with this patch as a matter of principle, but I'd like to understand what it fixes, add a test for that, and make sure that it doesn't break other stuff.

This is impossible to write a test for currently, since even with this fix, it still won't work (it needs several different patches, all of which need to be submitted before it starts working). I'm hoping you'll be satisfied with "it doesn't break anything existing, and @ian-twilightcoder it shouldn't be textual, so the current definition is incorrect".

FWIW, with this patch (and a few others, eg #132125), I've successfully built the whole of Chrome.

https://github.com/llvm/llvm-project/pull/130723