[libcxx-commits] [PATCH] D103947: [libcxx] Fix using the vcruntime ABI with _HAS_EXCEPTIONS=0 defined

[Reid Kleckner via Phabricator via libcxx-commits]

rnk added a comment.

I think we can say that `_HAS_EXCEPTIONS=0` is an important configuration. We use it in LLVM, you can grep for it:

  $ git grep _HAS_EXCEPTIONS ../llvm
  ../llvm/cmake/modules/AddLLVM.cmake:      list(APPEND LLVM_COMPILE_DEFINITIONS _HAS_EXCEPTIONS=0)
  ... others

Chromium also uses it, but apparently they already found this problem and worked around it:
https://source.chromium.org/chromium/chromium/src/+/main:build/config/compiler/BUILD.gn;l=1881?q=_HAS_EXCEPTIONS&ss=chromium

  # libc++ uses the __has_feature macro to control whether to use exceptions,
  # so defining this macro is unnecessary. Defining _HAS_EXCEPTIONS to 0 also
  # breaks libc++ because it depends on MSVC headers that only provide certain
  # declarations if _HAS_EXCEPTIONS is 1. Those MSVC headers do not use
  # exceptions, despite being conditional on _HAS_EXCEPTIONS.

I can't speak to or improve the state of libc++ testing, but I think we'd start using this configuration if libc++ supported it. We have plans to work on Windows testing in LLVM, and that might include libc++, but the timeline is early 2022, so I'm not sure we should wait for that.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D103947