[PATCH] D47169: [CMake] Use a different source depending on C++ support

[Jonas Hahnfeld via Phabricator via llvm-commits]

Hahnfeld added a comment.

In https://reviews.llvm.org/D47169#1141759, @phosek wrote:

> I never got any email, sorry about the lack of the response, I just noticed this because your revert broke our build.


The messages seem to be on `llvm-commits` (http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20180528/557038.html and http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20180611/thread.html#559742), but in any case you should have received a direct notification from Phabricator. Maybe you might want to check your filters?

> What is your build configuration where you're seeing the failure? I'd like to replicate the issue and try to come up with a better solution because now this is blocking us.

I'm on x86_64 but don't have a 32bit version of the C++ libraries (we are bootstrapping Clang with `libc++` and `-DCLANG_DEFAULT_CXX_STDLIB=libc++`). I think this configuration will become more important soon as distributions try to shave support for 32bit libraries and binaries.

The only "correct" solution that I can currently think of is fixing the dependency in `runtimes/` (which I assume you are using for Fuchsia):

1. Configure and compile `builtins`
2. Configure and compile `libunwind`, `libc++abi`, and `libc++`
3. Configure all other runtime libraries, including the sanitizers.

The other approach would be to kill the dependency of the sanitizers to the C++ library - I thought somebody wanted to tackle this in the past, but I'd need to look through the mailing lists.


Repository:
  rL LLVM

https://reviews.llvm.org/D47169