[all-commits] [llvm/llvm-project] 027184: [libc++] Guard the fix to CityHash behind ABI v2

[Louis Dionne via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 02718433a0dd3f8d3f3719b97aa1685b699ac785
      https://github.com/llvm/llvm-project/commit/02718433a0dd3f8d3f3719b97aa1685b699ac785
  Author: Louis Dionne <ldionne.2 at gmail.com>
  Date:   2023-02-09 (Thu, 09 Feb 2023)

  Changed paths:
    M libcxx/include/__config
    M libcxx/include/__functional/hash.h
    M libcxx/test/libcxx/utilities/utility/__murmur2_or_cityhash.pass.cpp

  Log Message:
  -----------
  [libc++] Guard the fix to CityHash behind ABI v2

As explained in a comment in https://reviews.llvm.org/D134124, we tried
landing this unconditionally but this actually bit some users who were
sharing std::unordered_map across an ABI boundary. This shows that the
ABI break is not benign and it should be guarded behind ABI v2.

Differential Revision: https://reviews.llvm.org/D143688