[cfe-dev] Clang 3.8 can't compile libunwind 3.9

[Renato Golin via cfe-dev]

Hi Logan,

So, I just realised clang 3.8 comes with an unwind.h which doesn't
have _URC_OK defined (introduced in r262178, just after 3.8 split).

But on that commit, the personality routine depends on it for EHABI
calls, which is defined by default on ARM environments.

The end result is that I can only use Clang 3.9+ to compile libunwind 3.9+.

http://buildmaster.tcwglab.linaro.org/builders/clang-cmake-armv7-a15-full/builds/1788/steps/build%20stage%201/logs/stdio

compiler-rt/lib/builtins/gcc_personality_v0.c:149:57: error: use of
undeclared identifier '_URC_OK'; did you mean '_UVRSR_OK'?
    if (__gnu_unwind_frame(exceptionObject, context) != _URC_OK)
                                                        ^~~~~~~

Do we take this as an ABI break and document it? Or do we try to fix it?

cheers,
--renato