[libcxx-commits] [PATCH] D104980: [libcxx][NFC] replaces `<utility>` includes with specific headers

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added a comment.

In D104980#2862532 <https://reviews.llvm.org/D104980#2862532>, @EricWF wrote:

> So we're splitting up the headers (which I don't love, but will hold my tongue for the most part).
>
> The intention is to provide better name hygene for our users. Meaning headers will export _fewer_ names than they do at present.
> This is an intentional BREAKING change. Users will have to update their code to include the correct headers before it will compile.
>
> Before we do this we need to:
>
> 1. Announce and discuss this change, it's rational, and its benefits to *all libc++ vendors*.
> 2. Document the list of names removed from every header. This list should be complete.
> 3. Ensure Clang's error messages tell users _which_ headers to include. Or at least don't tell users to include the wrong (implementation) headers.

It is indeed a breaking change, albeit one that is easy to remediate for users. But on a large scale, I agree it can be challenging to tackle.

While there is a clear benefit in making the headers less monolithic, minimizing the includes themselves is, as someone who just wants to ship an updated libc++, primarily a pain point. I'm willing to play ball and go through the pain of fixing my direct users (even though that's a huge pain), but if another vendor finds this change too disruptive, I can also get behind that. At the end of the day, the pain is real, but the benefit has a component of "pedantic correctness" to it. It would be a lot easier to make this change if we somehow could make it gradually, but I think the only way to do that would be for users to make sure their code always builds with modules enabled and disabled.


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