[PATCH][cxxabi] ARM EHABI zero-cost exception handling for libc++abi

[Logan Chien]

Hi all,

Sorry for the typo.

I was trying to build and test libc++abi from [1] but failed.  I have tried
to build the library by compiling all the *.cpp and *.c, but it seems not
working.  May you provide some instructions to build it?

BTW, I agree with Jonathan.  It seems that __ARM_EABI_UNWINDER__ is not
pre-defined.
I am not sure for __USING_SJLJ_EXCEPTIONS__ at the moment.  I will check
out ASAP.

Logan

[1]:
https://github.com/awong-dev/ndk/tree/use-libc%2B%2Babi/sources/cxx-stl/llvm-libc%2B%2Babi/libcxxabi
[2] http://www.sourceware.org/ml/libc-alpha/2004-02/msg00138.html


On Wed, Apr 16, 2014 at 7:58 PM, Logan Chien <tzuhsiang.chien at gmail.com>wrote:

> Hi Jonathan and Nick,
>
> I was trying to build libc++abi from repository but failed.  May you
> provide some instruction to cross compile libc++abi for ARM Linux?  Thanks.
>
> Logan
>
>
> On Tue, Apr 15, 2014 at 5:23 AM, Jonathan Roelofs <
> jonathan at codesourcery.com> wrote:
>
>>
>>
>> On 4/14/14, 1:51 PM, Nick Kledzik wrote:
>>
>>>
>>> On Apr 13, 2014, at 3:16 AM, Logan Chien <tzuhsiang.chien at gmail.com>
>>> wrote:
>>>
>>>  Hi,
>>>>
>>>> I have worked on ARM EHABI zero-cost exception handling for libc++abi.
>>>>
>>>> With the attached patch, I can compile and run all libc++abi unittests
>>>> on ARM Linux.
>>>>
>>>> Is it OK to commit?  Thanks.
>>>>
>>>>
>>>  diff --git a/include/unwind.h b/include/unwind.h
>>>> index c5acd93..e57d756 100644
>>>> --- a/include/unwind.h
>>>> +++ b/include/unwind.h
>>>> @@ -23,8 +23,24 @@
>>>>   #define LIBUNWIND_UNAVAIL
>>>>   #endif
>>>>
>>>> +#if !defined(LIBCXXABI_SJLJ)
>>>> +#  if defined(__arm__)
>>>> +#    if defined(__APPLE__)
>>>> +#      define LIBCXXABI_ARM_EHABI 0
>>>> +#      define LIBCXXABI_SJLJ 1
>>>> +#    else
>>>> +#      define LIBCXXABI_ARM_EHABI 1
>>>> +#      define LIBCXXABI_SJLJ 0
>>>> +#    endif
>>>> +#  else
>>>> +#    define LIBCXXABI_ARM_EHABI 0
>>>> +#    define LIBCXXABI_SJLJ 0
>>>> +#  endif
>>>> +#endif
>>>>
>>> I recently found that the compiler has a built-in define
>>>  __USING_SJLJ_EXCEPTIONS__ that is set when compiling for setjump/longjump
>>> based exceptions.  Is there are similar built-in for ARM EHABI?  If so, we
>>> can set these up without testing for __arm__ or __APPLE__.  In fact,
>>> LIBCXXABI_SJLJ can be replaced with __USING_SJLJ_EXCEPTIONS__.  And perhaps
>>> LIBCXXABI_ARM_EHABI can be replaced with some built-in?
>>>
>> __ARM_EABI_UNWINDER__ perhaps?  I'm not exactly sure what the semantics
>> of it are, and I don't see a definition for it in Clang.  In libgcc's
>> unwinder it's defined in one of the arm config files. I suppose that makes
>> it not a builtin then....
>>
>>>
>>>  diff --git a/src/cxa_exception.cpp b/src/cxa_exception.cpp
>>>> index 744dddd..27a55c5 100644
>>>> --- a/src/cxa_exception.cpp
>>>> +++ b/src/cxa_exception.cpp
>>>> @@ -232,7 +232,7 @@ __cxa_throw(void* thrown_object, std::type_info*
>>>> tinfo, void (*dest)(void*))
>>>>       globals->uncaughtExceptions += 1;   // Not atomically, since
>>>> globals are thread-local
>>>>
>>>>       exception_header->unwindHeader.exception_cleanup =
>>>> exception_cleanup_func;
>>>> -#if __arm__
>>>> +#if LIBCXXABI_SJLJ
>>>>       _Unwind_SjLj_RaiseException(&exception_header->unwindHeader);
>>>>   #else
>>>>
>>> I like the conditional test for SJLJ instead of the processor, but as I
>>> recently discovered, most of the existing __arm__ tests can be changed to
>>> __USING_SJLJ_EXCEPTIONS__ tests.
>>>
>>> -Nick
>>>
>>>
>>> _______________________________________________
>>> cfe-commits mailing list
>>> cfe-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>>
>>>
>> --
>> Jon Roelofs
>> jonathan at codesourcery.com
>> CodeSourcery / Mentor Embedded
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>
>
>
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