[libcxx-commits] [libcxx] [libc++] Fix iostream size ABI break (PR #185839)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

It's pretty awful that the symbol size leaks into the ABI like this -- it's definitely the first time I come across this property. About testing, I don't think we need to add anything else: we could have caught this break right in #124103 as our tests actually highlighted the change, but we did not know this was an ABI affecting property.

So LGTM with small comments. Let's get this cherry-picked.

https://github.com/llvm/llvm-project/pull/185839