[cfe-dev] libcxxabi cmake test problem on Linux x86-64

Eric Fiselier via cfe-dev cfe-dev at lists.llvm.org
Thu Dec 10 19:50:54 PST 2015


Alright, so the problem is that libgcc_eh.a marks most of the _Unwind
symbols as hidden. This means that when libgcc_eh.a is linked into a shared
library exceptions cannot be thrown beyond the library boundary. I think
that both libgcc_s and libgcc_eh were being linked into lli causing the
failures. Since we typically build libc++abi as a shared library we need to
use libgcc_s.so instead. (I think we will still need to use libgcc_eh when
creating a static libc++abi)

I think that libc++abi should link the default libraries exactly as clang
would if we didn't specify '-nodefaultlibs`.  This resulting link line for
libc++abi.so should look something like:

   -lm -lgcc_s -lpthread -lc -lgcc_s

The resulting libc++abi.so will still have undefined references to
libgcc.a's _Unwind symbols but libgcc.a should always be linked into the
final executable.
When using and testing libc++abi (via libc++) the link line should look
something like:

   -lc++ -lm -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc

When we want to use llvm's unwinder we will probably need to use -lunwind
-lcompiler-rt instead but I'm not too familiar with this configuration.

I'll put a patch together tonight.

/Eric

On Thu, Dec 10, 2015 at 6:26 PM, Eric Fiselier <eric at efcs.ca> wrote:

> I've spent most of today looking into this and I still have no clue what's
> going on. I think I need to know more about how lli provides libc++.
>
> I was able to reproduce the bug using the following steps:
>
> 1. export CC=clang CXX=clang++
> 2. cmake --DLLVM_ENABLE_LIBCXX=ON -DLLVM_BUILD_PROJECTS=OFF../llvm
> 3. ./bin/lli llvm/test/ExecutionEngine/MCJIT/eh.ll
>
> The above steps assume that you already have libc++.so installed somewhere
> the linker can find it
> and that libc++.so is a linker script that includes -lc++abi.
>
> I turned LLVM_BUILD_PROJECTS off so that we aren't contending with two
> different libc++abi binaries.
>
> Any help with this bug would be appreciated.
>
> /Eric
>
> On Wed, Dec 9, 2015 at 12:27 PM, Chandler Carruth <chandlerc at google.com>
> wrote:
>
>> Yep.
>>
>> On Wed, Dec 9, 2015 at 8:21 PM Eric Fiselier <eric at efcs.ca> wrote:
>>
>>> I don't remember what's going on here but alot has changed in a year. I
>>> should be able to look into it later today.
>>>
>>> Chandler, I'm assuming your still able to reproduce the issue?
>>>
>>> /Eric
>>>
>>> On Wed, Dec 9, 2015 at 3:06 AM, Chandler Carruth <chandlerc at google.com>
>>> wrote:
>>>
>>>> (Moving to the new mailing list)
>>>>
>>>> On Wed, Nov 26, 2014 at 10:09 PM Evgeniy Stepanov <
>>>> eugeni.stepanov at gmail.com> wrote:
>>>>
>>>>> #0  0x00007ffff62b5bb9 in __GI_raise (sig=sig at entry=6) at
>>>>> ../nptl/sysdeps/unix/sysv/linux/raise.c:56
>>>>> #1  0x00007ffff62b8fc8 in __GI_abort () at abort.c:89
>>>>> #2  0x00007ffff7b60807 in abort_message (format=0x7ffff7bcdf13
>>>>> "terminating with %s exception of type %s") at
>>>>> ../projects/libcxxabi/src/abort_message.cpp:66
>>>>> #3  0x00007ffff7b60ad6 in default_terminate_handler () at
>>>>> ../projects/libcxxabi/src/cxa_default_handlers.cpp:68
>>>>> #4  0x00007ffff7bc454e in std::__terminate (func=0x7ffff7b60900
>>>>> <default_terminate_handler()>) at
>>>>> ../projects/libcxxabi/src/cxa_handlers.cpp:68
>>>>> #5  0x00007ffff7bc31dd in __cxxabiv1::failed_throw
>>>>> (exception_header=0x1e87240) at
>>>>> ../projects/libcxxabi/src/cxa_exception.cpp:149
>>>>> #6  0x00007ffff7bc3136 in __cxa_throw (thrown_object=0x1e872b8,
>>>>> tinfo=0x7ffff7dd83b0 <typeinfo for int>, dest=0x0) at
>>>>> ../projects/libcxxabi/src/cxa_exception.cpp:244
>>>>> #7  0x00007ffff7ff502d in throwException ()
>>>>> #8  0x00007ffff7ff503d in main ()
>>>>> #9  0x0000000000beef04 in llvm::MCJIT::runFunction (this=0x1e74c30,
>>>>> F=0x1e6b4b0, ArgValues=...) at
>>>>> ../lib/ExecutionEngine/MCJIT/MCJIT.cpp:500
>>>>> #10 0x0000000000b26f90 in llvm::ExecutionEngine::runFunctionAsMain
>>>>> (this=0x1e74c30, Fn=0x1e6b4b0, argv=..., envp=0x7fffffffe0d0)
>>>>>     at ../lib/ExecutionEngine/ExecutionEngine.cpp:393
>>>>> #11 0x0000000000567cc4 in main (argc=4, argv=0x7fffffffe0a8,
>>>>> envp=0x7fffffffe0d0) at ../tools/lli/lli.cpp:613
>>>>>
>>>>
>>>> Any update here Eric? Or others? Would really like to get the bootstrap
>>>> clean with libc++abi.
>>>>
>>>>
>>>>>
>>>>> On Wed, Nov 26, 2014 at 11:37 PM, Eric Fiselier <eric at efcs.ca> wrote:
>>>>> > Evgeniy,
>>>>> >
>>>>> > Would you be willing to reproduce this again but in debug mode
>>>>> instead
>>>>> > of release so we get a better stack trace?
>>>>> >
>>>>> > /Eric
>>>>> >
>>>>> > On Wed, Nov 26, 2014 at 5:20 AM, Evgeniy Stepanov
>>>>> > <eugeni.stepanov at gmail.com> wrote:
>>>>> >> I've got the same issue.
>>>>> >> On Linux (Trusty/x86_64), build clang with libc++/libc++abi (just
>>>>> >> plain ninja clang cxx cxxabi w/o any special cmake flags), then use
>>>>> it
>>>>> >> to bootstrap clang like this:
>>>>> >>
>>>>> >> CC=/code/llvm/build2/bin/clang \
>>>>> >> CXX=/code/llvm/build2/bin/clang++ \
>>>>> >> LDFLAGS="-lc++abi -L/code/llvm/build2/lib
>>>>> -Wl,-rpath,/code/llvm/build2/lib" \
>>>>> >> cmake \
>>>>> >>   -GNinja \
>>>>> >>   -DCMAKE_BUILD_TYPE=Release \
>>>>> >>   -DLLVM_ENABLE_LIBCXX=ON  \
>>>>> >>   ..
>>>>> >>
>>>>> >> In the second tree, MCJIT tests fail with the same error:
>>>>> >>
>>>>> >> ./bin/lli -relocation-model=pic -code-model=large
>>>>> >> ../test/ExecutionEngine/MCJIT/eh-lg-pic.ll
>>>>> >> terminating with uncaught exception of type int
>>>>> >> 0  lli             0x0000000000a80a9a
>>>>> >> _ZN4llvm3sys15PrintStackTraceEP8_IO_FILE + 42
>>>>> >> 1  lli             0x0000000000a81eeb
>>>>> >> 2  libpthread.so.0 0x00007f83baabf340
>>>>> >> 3  libc.so.6       0x00007f83b9d2fbb9 gsignal + 57
>>>>> >> 4  libc.so.6       0x00007f83b9d32fc8 abort + 328
>>>>> >> 5  libc++abi.so.1  0x00007f83bb5121a7
>>>>> >> 6  libc++abi.so.1  0x00007f83bb512355
>>>>> >> 7  libc++abi.so.1  0x00007f83bb55c3b3
>>>>> >> 8  libc++abi.so.1  0x00007f83bb55bb66 __cxa_throw + 166
>>>>> >> 9  libc++abi.so.1  0x00007f83bb98802d __cxa_throw + 4375917
>>>>> >> 10 libc++abi.so.1  0x00007f83bb98803d __cxa_throw + 4375933
>>>>> >> 11 lli             0x0000000000849649
>>>>> >>
>>>>> _ZN4llvm5MCJIT11runFunctionEPNS_8FunctionERKNSt3__16vectorINS_12GenericValueENS3_9allocatorIS5_EEEE
>>>>> >> + 1209
>>>>> >> 12 lli             0x00000000007ecd08
>>>>> >>
>>>>> _ZN4llvm15ExecutionEngine17runFunctionAsMainEPNS_8FunctionERKNSt3__16vectorINS3_12basic_stringIcNS3_11char_traitsIcEENS3_9allocatorIcEEEENS8_ISA_EEEEPKPKc
>>>>> >> + 1192
>>>>> >> 13 lli             0x000000000050c434 main + 10404
>>>>> >> 14 libc.so.6       0x00007f83b9d1aec5 __libc_start_main + 245
>>>>> >> 15 lli             0x00000000005092fb
>>>>> >> Stack dump:
>>>>> >> 0. Program arguments: ./bin/lli -relocation-model=pic
>>>>> >> -code-model=large ../test/ExecutionEngine/MCJIT/eh-lg-pic.ll
>>>>> >> Aborted (core dumped)
>>>>> >>
>>>>> >> On Sat, Aug 16, 2014 at 9:24 AM, İsmail Dönmez <ismail at donmez.ws>
>>>>> wrote:
>>>>> >>> Ping?
>>>>> >>>
>>>>> >>> On Jul 17, 2014 11:05 AM, "İsmail Dönmez" <ismail at donmez.ws>
>>>>> wrote:
>>>>> >>>>
>>>>> >>>> Hi,
>>>>> >>>>
>>>>> >>>>
>>>>> >>>> On Wed, Jul 16, 2014 at 6:43 PM, Nico Weber <thakis at chromium.org>
>>>>> wrote:
>>>>> >>>>>
>>>>> >>>>> On Wed, Jul 16, 2014 at 4:10 AM, İsmail Dönmez <ismail at donmez.ws>
>>>>> wrote:
>>>>> >>>>>>
>>>>> >>>>>> Hi,
>>>>> >>>>>>
>>>>> >>>>>>
>>>>> >>>>>> On Mon, Jul 14, 2014 at 8:10 PM, Dan Albert <
>>>>> danalbert at google.com>
>>>>> >>>>>> wrote:
>>>>> >>>>>>>
>>>>> >>>>>>> Submitted (with some slight modifications,
>>>>> s/libgcc_s/libgcc_eh/) as
>>>>> >>>>>>> r212958. Tested with and without the LLVM unwinder, and things
>>>>> look good.
>>>>> >>>>>>> Thanks again!
>>>>> >>>>>>
>>>>> >>>>>>
>>>>> >>>>>> Changing gcc_s with gcc_eh doesn't look good. libcxxabi tests
>>>>> pass but
>>>>> >>>>>> llvm MCJIT exception tests fail with:
>>>>> >>>>>>
>>>>> >>>>>> "terminating with uncaught exception of type int"
>>>>> >>>>>
>>>>> >>>>>
>>>>> >>>>> Can you try to make a reduced test case for libcxxabi from this?
>>>>> >>>>>
>>>>> >>>>
>>>>> >>>>
>>>>> >>>>
>>>>> >>>> Smallest test cases are
>>>>> >>>> test/ExecutionEngine/MCJIT/{eh-sm-pic,eh-lg-pic}.ll
>>>>> >>>>
>>>>> >>>> Both fail the same way:
>>>>> >>>>
>>>>> >>>>  /home/abuild/rpmbuild/BUILD/llvm/stage2/./bin/lli -use-mcjit
>>>>> >>>> -relocation-model=pic -code-model=small
>>>>> >>>>
>>>>> /home/abuild/rpmbuild/BUILD/llvm/test/ExecutionEngine/MCJIT/eh-sm-pic.ll
>>>>> >>>>  --
>>>>> >>>>  Exit Code: 134
>>>>> >>>>
>>>>> >>>>  Command Output (stderr):
>>>>> >>>>  --
>>>>> >>>>  terminating with uncaught exception of type int
>>>>> >>>>  0  libLLVMSupport.so         0x00007f9c6ddf7d85
>>>>> >>>> llvm::sys::PrintStackTrace(_IO_FILE*) + 37
>>>>> >>>>  1  libLLVMSupport.so         0x00007f9c6ddf83f3
>>>>> >>>>  2  libpthread.so.0           0x00007f9c6d0d79f0
>>>>> >>>>  3  libc.so.6                 0x00007f9c6c806849 gsignal + 57
>>>>> >>>>  4  libc.so.6                 0x00007f9c6c807cd8 abort + 328
>>>>> >>>>  5  libc++abi.so.1            0x00007f9c6cb89237
>>>>> >>>>  6  libc++abi.so.1            0x00007f9c6cb894b6
>>>>> >>>>  7  libc++abi.so.1            0x00007f9c6cbeda7e
>>>>> >>>>  8  libc++abi.so.1            0x00007f9c6cbec6ed
>>>>> >>>>  9  libc++abi.so.1            0x00007f9c6cbec646
>>>>> >>>>  10 libc++abi.so.1            0x00007f9c6ff3001c
>>>>> >>>>  11 libc++abi.so.1            0x00007f9c6ff30026
>>>>> >>>>  12 libLLVMMCJIT.so           0x00007f9c6e61fd27
>>>>> >>>> llvm::MCJIT::runFunction(llvm::Function*,
>>>>> >>>> std::__1::vector<llvm::GenericValue,
>>>>> std::__1::allocator<llvm::GenericValue>
>>>>> >>>> > const&) + 919
>>>>> >>>>  13 libLLVMExecutionEngine.so 0x00007f9c6f34fa65
>>>>> >>>> llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*,
>>>>> >>>> std::__1::vector<std::__1::basic_string<char,
>>>>> std::__1::char_traits<char>,
>>>>> >>>> std::__1::allocator<char> >,
>>>>> >>>> std::__1::allocator<std::__1::basic_string<char,
>>>>> >>>> std::__1::char_traits<char>, std::__1::allocator<char> > > >
>>>>> const&, char
>>>>> >>>> const* const*) + 1221
>>>>> >>>>  14 lli                       0x000000000040c8b7 main + 6599
>>>>> >>>>  15 libc.so.6                 0x00007f9c6c7f2be5
>>>>> __libc_start_main + 245
>>>>> >>>>  16 lli                       0x000000000040a6d1
>>>>> >>>>  Stack dump:
>>>>> >>>>  0. Program arguments:
>>>>> /home/abuild/rpmbuild/BUILD/llvm/stage2/./bin/lli
>>>>> >>>> -use-mcjit -relocation-model=pic -code-model=small
>>>>> >>>>
>>>>> /home/abuild/rpmbuild/BUILD/llvm/test/ExecutionEngine/MCJIT/eh-sm-pic.ll
>>>>> >>>>
>>>>> >>>>
>>>>> /home/abuild/rpmbuild/BUILD/llvm/stage2/test/ExecutionEngine/MCJIT/Output/eh-sm-pic.ll.script:
>>>>> >>>> line 1: 30636 Aborted
>>>>> >>>> /home/abuild/rpmbuild/BUILD/llvm/stage2/./bin/lli -use-mcjit
>>>>> >>>> -relocation-model=pic -code-model=small
>>>>> >>>>
>>>>> /home/abuild/rpmbuild/BUILD/llvm/test/ExecutionEngine/MCJIT/eh-sm-pic.ll
>>>>> >>>>
>>>>> >>>> Note that this clang is hardcoded to use libc++
>>>>> (-stdlibc=libc++). Is this
>>>>> >>>> good enough?
>>>>> >>>>
>>>>> >>>> Thanks!
>>>>> >>>>
>>>>> >>>
>>>>> >>> _______________________________________________
>>>>> >>> cfe-dev mailing list
>>>>> >>> cfe-dev at cs.uiuc.edu
>>>>> >>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>> >>>
>>>>> >>
>>>>> >> _______________________________________________
>>>>> >> cfe-dev mailing list
>>>>> >> cfe-dev at cs.uiuc.edu
>>>>> >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>>
>>>>> _______________________________________________
>>>>> cfe-dev mailing list
>>>>> cfe-dev at cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>>
>>>>
>>>
>
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