[cfe-dev] unraveling libcxxabi/libcxx

[David Fang]

Hi Howard,

I whipped up another Makefile to compile tests to different executables, 
where the resulting commands look like:

/Users/fang/local/src/LLVM-svn/gcc40-cmake-build/bin/clang++ -std=c++0x 
-stdlib=libc++ -O0 -no-integrated-as -I../include -cxx-isystem 
/usr/local/experimental/llvm/lib/libcxx/include/c++/v1 
-I/usr/lib/gcc/powerpc-apple-darwin8/4.0.1/include unwind_01.cpp 
../lib/libc++abi.1.dylib -L/usr/local/experimental/llvm/lib/libcxx/lib  -o 
unwind_01

Unfortunately, I get a ton of test failures.  Just to pick one 
arbitrarily:

% env DYLD_LIBRARY_PATH=../lib gdb ./unwind_01
GNU gdb 6.3.50-20050815 (Apple version gdb-696) (Sat Oct 20 18:20:28 GMT 
2007)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you 
are
welcome to change it and/or distribute copies of it under certain 
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for 
details.
This GDB was configured as "powerpc-apple-darwin"...
warning: --arch option not supported in this gdb.
Reading symbols for shared libraries ..... done

(gdb) run
Starting program: 
/Volumes/Isolde/sources/LLVM-svn/libcxxabi.git/test/unwind_01
tcsh: Word too long.
Reading symbols for shared libraries .++ done
libc++abi.dylib: terminating with uncaught exception of type int

Program received signal SIGABRT, Aborted.
0x90047dac in kill ()
(gdb) where
#0  0x90047dac in kill ()
#1  0x9012d7b4 in abort ()
#2  0x00205a18 in abort_message ()
#3  0x00205ce0 in _ZL25default_terminate_handlerv ()
#4  0x00214738 in std::__terminate ()
#5  0x00215888 in __cxxabiv1::call_terminate ()
#6  0x0021580c in __cxxabiv1::scan_eh_tab ()
#7  0x00214d38 in __gxx_personality_v0 ()
#8  0x9143cbc0 in _Unwind_RaiseException ()
#9  0x00212cd4 in __cxa_throw ()
#10 0x000020c8 in f2 ()
#11 0x0000212c in f1 ()
#12 0x000021cc in main ()

I see how unwind_01.cpp is supposed to work.  Any idea why
"throw 55;" isn't getting caught by catch(int)?

The libunwind I'm using happens to be the one shipped with libgcc_s.10.4.
Not sure what Apple version number that would correspond to.

How can I go about debugging this?

Fang


> On OS X, you can:
>
> export DYLD_LIBRARY_PATH=<path-to-libcxx>/lib
> clang++ -std=c++11 -stdlib=libc++ -nostdinc++ -I<path-to-libcxx>/include -L<path-to-libcxx>/lib test.cpp
>
> (sub in libc++abi where appropriate).  The DYLD_LIBRARY_PATH symbol can contain multiple paths, using ':' as a separator.
>
> Howard
>
> On Apr 3, 2013, at 6:30 PM, David Fang <fang at csl.cornell.edu> wrote:
>
>> Hi Howard and all,
>>
>> I was able to build libcxxabi and libcxx on powerpc-darwin8.
>> I've documented my experiences here. http://www.csl.cornell.edu/~fang/sw/llvm/#libcxx
>>
>> I might need some explanation for how the test suite is expected to be run.  The 'testit' script in libcxxabi doesn't even refer to the libc++abi.dylib that was built, so there must be some implicit assumptions in this script?
>>
>> I'm hoping there's a way to test the dylib before having to install it.
>> Likewise with libc++.
>>
>> Fang
>>
>>> On Apr 2, 2013, at 8:35 PM, David Fang <fang at csl.cornell.edu> wrote:
>>>
>>>> Hi,
>>>> 	I'm currently looking into porting libcxx to an ancient system (powerpc-darwin8), and I noticed that libcxx depends on libcxxabi. However, libcxxabi's sources include headers like <exception> which are expected to be in some C++ library.  Does it (mutually) depend on libcxx? Maybe this was obvious, but I take it libcxxabi needs a c++11 compiler to build, correct?  (This would be fine, as I have stage-1 clang built from gcc-4.0/libstdc++.)  Does one {libcxx,libcxxabi} need to be installed before the other, or should they be built cross-referencing each others include dirs?  In terms of shared-library dependencies, libcxx should link to libcxxabi, right?
>>>>
>>>> Is there better documentation somewhere that I don't know about?
>>>> All I see are html pages at http://libcxxabi.llvm.org and http://libcxx.llvm.org/.
>>>
>>> Contributions to better documentation (and your experiences in doing this) are welcome. :-)
>>>
>>> Yes, libcxxabi is the lower-level library.  libcxx should link to libcxxabi.
>>>
>>> Yes, currently libcxxabi is using -std=c++0x and probably needs it, though I can't think offhand of a specific need.  If you need to, try changing that to -std=c++03.  If there's any breakage it will almost certainly be compile-time breakage.  So that is a safe experiment.
>>>
>>> libcxxabi is designed to be ABI compatible with a gcc-4.2 era libstdc++.  And therefore could almost certainly use a libstdc++-4.2 set of headers if need be to build against (another untested theory).
>>>
>>> As libcxxabi is the lower-level library, I would go with installing that first.  But understand you're traversing territory where few have gone before.
>>>
>>> Keep us posted, and blogs of your experience which might help future porters are welcome.
>>>
>>> Howard
>>>
>>
>> --
>> David Fang
>> http://www.csl.cornell.edu/~fang/
>>
>

-- 
David Fang
http://www.csl.cornell.edu/~fang/