[libcxx-commits] [libcxx] [libc++] Remove ios_base::__xindex_ from the ABI (PR #198994)

[Eli Friedman via libcxx-commits]

efriedma-quic wrote:

Opened #208356 to restore the old behavior with `LIBCXX_ENABLE_THREADS=OFF`.

Bug #131365 describes the issue that `LIBCXX_ENABLE_THREADS` doesn't mean what we want it to mean.

https://github.com/llvm/llvm-project/pull/198994