[libcxx-dev] Support for older MacOS systems

[Ken Cunningham via libcxx-dev]

On 2019-04-01, at 10:14 AM, Louis Dionne wrote:

> Looking at the specific issue further, I think the current trunk version of libc++ should build on old systems just fine. Without the workaround, we'll be re-exporting the hard-coded list of symbols in libc++abi.v2.exp instead of all the symbols in the libc++abi.dylib, but those should be equivalent. Can you please comment on whether trunk seems to work for you?
> 
> Thanks,
> Louis
> 

Indeed clang-trunk and llvm-trunk build through to completion on all systems, 10.6 and up, including building libcxx during the clang build. I haven't tried the 10.5 trunk builds as yet.

We tend to lag a bit behind trunk with our libcxx releases, and currently we are installing libcxx 5.0.

I have installed libcxx 7.0 on my personal 10.6.8 systems to test it, and have found no notable issues with that version. 

The only flags during testing are the minor ones expected from using -femulated-tls on Darwin, as it's not expected by the test suite for Darwin to be using cxa_thread_atexit as we are doing on those systems, instead of tlv_atexit.

I am often amazed at just how well it all works, and how something as complex as llvm, clang, and libcxx can build through on 10.5 or 10.6.8 with hardly a hiccup or compiler warning.

Kudos.

Ken