[cfe-dev] [libcxxabi] Contributing ARM EHABI support for libcxxabi

Nick Kledzik kledzik at apple.com
Wed Dec 4 14:44:40 PST 2013

On Dec 4, 2013, at 12:56 PM, Nico Weber <thakis at chromium.org> wrote:

> > 3.) r192136 didn’t add any test – how should testing of unwinding code work? Is running the exception tests in the libc++ suite enough?
> The Darwin libunwind project (http://opensource.apple.com/source/libunwind/libunwind-35.3/) on which this was based had some a small test suite, but it did not fit into the existing libcxxabi test suite which assumes target==host and every test is one .cpp file.
> Ok. I tried running at least the libc++abi test suite to make sure we don't completely break exception handling on darwin, but it looks like the buildit script doesn't build libunwind, and if I try to get it to compile (attached), the compiler complains about mach-o/dyld_priv.h – is it currently possible to run libc++abi tests for the Unwind bits of libc++abi on darwin?
> If I copy http://www.opensource.apple.com/source/dyld/dyld-132.13/include/mach-o/dyld_priv.h?txt to include/mach-o/dyld_priv.h and build with the attached script, I'm able to build a libunwind.dylib that passes the tests and that fails them if I add an early return to _Unwind_RaiseException. Would adding dyld_priv.h and landing the attached patch be a good first step?

Regarding dyld_priv.h, since it is always on my system in /usr/local/include, I had not realized the unwinder had that dependency.  I posted a patch earlier to get the unwinder building on older darwins which did not have dyld support.  I can update that patch so that the unwinder never need dyld_priv.h.

Regarding the build system, I think it brings up the bigger issue of what sort of build system we want for libcxxabi.  The script is a quick way to get building.  But, it is not how Apple actual builds the shipping libunwind (which is a local xcode project).  What sort of build system would others like?


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