[libcxx-commits] [PATCH] D97572: [libc++] Include <__config_site> from <__config>

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added a comment.

In D97572#2835202 <https://reviews.llvm.org/D97572#2835202>, @phosek wrote:

> We could put it behind a CMake option that's going to be opt-in, for example `LIBCXX_GENERIC_CONFIG_SITE`, would that work?
>
> @ldionne do you have any other ideas? Would this be OK with you?

Stumbled upon this months later while clearing my email queue, I hope the discussion is still relevant.

@bjope What is the intent when compiling for `--target=powerpc64le-unknown-linux-gnu` with a library that has only been built for `x86_64-unknown-linux-gnu`? Is the intent that the `__config_site` used for `powerpc64le-unknown-linux-gnu` is the same as the one for `x86_64-unknown-linux-gnu`? To me, that sounds like something we can't really guess. I think what I'm wondering here is why you're using `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON` at all.

Having a fallback is indeed tricky because we really want to avoid at all costs using the wrong `__config_site` by mistake (this could lead to incredibly tricky errors including ABI breaks). I would also really like to avoid adding an opt-in for this - there has to be a better solution.


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https://reviews.llvm.org/D97572