[PATCH] D132324: [RFC] Remove support for building libc++ with `LLVM_ENABLE_PROJECTS`

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D132324#3742605 <https://reviews.llvm.org/D132324#3742605>, @ldionne wrote:

> This sucks, but I'm going to revert this series of patches. This is getting somewhat out of hands and I feel that we're rushing to fix all kinds of issues in various directions. I'm going to revert the following patches, in this order:
>
> 1. 952f90b72b35 <https://reviews.llvm.org/rG952f90b72b3546d6b6b038d410f07ce520c59b48> [CMake] Weaken 176db3b3ab25ff8a9b2405f50ef5a8bd9304a6d5 <https://reviews.llvm.org/rG176db3b3ab25ff8a9b2405f50ef5a8bd9304a6d5>
> 2. e6a0800532bb <https://reviews.llvm.org/rGe6a0800532bb409f6d1c62f3698bdd6994a877dc> [libcxxabi][cmake] Allow building without libcxx again
> 3. 176db3b3ab25 <https://reviews.llvm.org/rG176db3b3ab25ff8a9b2405f50ef5a8bd9304a6d5> [RFC] Remove support for building C++ with `LLVM_ENABLE_PROJECTS`
>
> Otherwise:
>
> - I also think we don't want to move forward with D132411 <https://reviews.llvm.org/D132411> -- it's going against this transition.
> - https://reviews.llvm.org/rZORG3a209ca6c1b9 sounds like a good change we'd need to make no matter what, so that's great.
> - D132454 <https://reviews.llvm.org/D132454> seems like a good change regardless of this series of patches.
>
> I think that's the whole set of changes/reviews associated to this in the past few days. If I've missed anything, please let me know ASAP.
>
> This will have been extremely useful as a way to shake out places where the deprecated `LLVM_ENABLE_PROJECTS` build is still being used for libc++/libc++abi. However, we should take the time to fix these places first before landing the actual breaking change, otherwise things become too unstable and we're rushed into making potentially poor decisions.
>
> Concretely, as an action item to move this transition forward, I will:
>
> 1. Grep for places where we still use `LLVM_ENABLE_PROJECTS` for libc++ and libc++abi in the LLVM monorepo
> 2. Do the same in the llvm-zorg repo
> 3. Do the same in our downstream bots (if other folks see this because of downstream breakage in their forks, be proactive and do this too, or you will get broken in the future!)
> 4. Re-land a patch that turns the `WARNING` into a `FATAL_ERROR`, and just that. Watch for more breakage and try fixing it iteratively.
> 5. Once we have `FATAL_ERROR` in place and things are green, we can land the rest of this patch (plus a few other things I had locally) to actually remove support for `LLVM_ENABLE_PROJECTS` with libc++/libc++abi.

Thank you @ldionne -- I think this plan of action makes sense to me. The disruption from reverts is unfortunate, but I think it's better to take a clean run at this once we have everything lined up and ready in the other projects.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D132324/new/

https://reviews.llvm.org/D132324