[libcxx-commits] [libcxx] Commit mostly working single wrapped module map (PR #87402)

[Vassil Vassilev via libcxx-commits]

vgvassilev wrote:

> It will only work if the libc++ module map is the only module map on the system, or if you start adding [no_undeclared_includes] hacks to the system module maps.

This is not a hack. It is quite well explained what that does in llvm/llvm-project at ed84df008f609.

> Out of the box only the Apple SDK supports clang modules.

That is quite incorrect. Our framework for large scale data analysis [ROOT](https://root.cern), supports modules on Linux and OSX since 2017 and everything worked pretty well before these changes...

> This change will definitely break on Apple systems, though the ones in CI are too old to exhibit the breakage.

That's very abstract. Could you please give us something to work with?

> @EricWF Do you still want to pursue this patch?

Our infrastructure at CERN depends on a single module of STL for performance, distribution and integration reasons on OSX. I'd like to pursue this patch or anything else that brings back the old behavior. I am not sure what the concerns of @ian-twilightcoder are concretely. I'd be happy to help if we can see a reproducible setup.

cc: @hahnjo, @dpiparo.

https://github.com/llvm/llvm-project/pull/87402