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

Nico Weber thakis at chromium.org
Wed Dec 4 15:18:02 PST 2013

Given that cmake is used widely in the rest of llvm, it makes sense to me
to use it here too – but Howard has expressed resistance in the past, so I
guess it's up to him :-) Maybe that decision can be made independent of the
rest and we can go with the tweak to what is there today?

On Wed, Dec 4, 2013 at 3:08 PM, Chandler Carruth <chandlerc at google.com>wrote:

> On Wed, Dec 4, 2013 at 2:44 PM, Nick Kledzik <kledzik at apple.com> wrote:
>> 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?
> Unless there is an overwhelming need to invest in something more custom, I
> would vote for cmake. I'm still holding out hope for an end to build system
> proliferation.
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