[cfe-dev] Can't compile simple OpenMP code with clang 5.0.0

Tue Dec 22 15:37:46 PST 2020

The command:
$ clang-10 -fopenmp foo.cxx
 
gives the error output:
/usr/bin/ld: /tmp/foo-e2d536.o: in function `__clang_call_terminate':
foo.cxx:(.text.__clang_call_terminate[__clang_call_terminate]+0x2): undefined reference to `__cxa_begin_catch'
/usr/bin/ld: foo.cxx:(.text.__clang_call_terminate[__clang_call_terminate]+0xb): undefined reference to `std::terminate()'
/usr/bin/ld: /tmp/foo-e2d536.o:(.eh_frame+0x4b): undefined reference to `__gxx_personality_v0'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
  
>Среда, 23 декабря 2020, 2:33 +03:00 от Johannes Doerfert <johannesdoerfert at gmail.com>:
> 
>I think libomp is still on version 5.0, (I know, I know).
>It is not coupled to LLVM wrt. version numbers.
>
>Last time I checked, LLVM build for debian (and Ububuntu)
>came bundled with the OpenMP runtimes (for the host). That
>means you should not need libomp-5-dev but just clang-10.
>libomp-5-dev is useful if you *don't* want clang but still
>target libomp, which is the LLVM OpenMP host runtime, from
>gcc, thus use it as a replacement of libgomp.
>
>All that said, doesn't `clang-10 -fopenmp ...` "just work"?
>
>~ Johannes
>
>
>On 12/22/20 5:28 PM, Керим Хемраев wrote:
>> Hi Johannes,
>>
>> Thank you for response
>>
>> It seems that I don’t have   libthread. Moreover it is highly likely that omp.h and libomp.so that I used to provide as parameters to clang are not shipped with clang 5 :)
>>
>> I think I should now forget about xeus-cling for a while and simply build the code with latest (or any) version of clang with OpenMP.
>>
>> I’ve tried to do the following:
>> $ sudo apt-get install clang-10
>> $ sudo apt-get install libomp-5-dev
>>
>> Now I want to find where are these packages were installed:
>> $ find  /usr -iname clang-10
>> /usr/lib/llvm-10/bin/clang-10
>> /usr/lib/cmake/clang-10
>> /usr/share/doc/clang-10
>> /usr/share/bash-completion/completions/clang-10
>> /usr/share/lintian/overrides/clang-10
>> /usr/bin/clang-10
>>
>> $ find  /usr -iname libomp-10-dev
>> /usr/share/doc/libomp-10-dev
>>
>> So I’m afraid that  libomp-10-dev  contains only some docs and there is no library   libomp-10-dev.so (or something)
>>
>> Could you please guide me how to properly install clang with OpenMP that I could build my test script?
>>
>> I’m on Ubuntu  20.04, x64
>> $ cat /etc/lsb-release
>> DISTRIB_ID=Ubuntu
>> DISTRIB_RELEASE=20.04
>> DISTRIB_CODENAME=focal
>> DISTRIB_DESCRIPTION="Ubuntu 20.04.1 LTS"
>>
>>> Среда, 23 декабря 2020, 0:48 +03:00 от Johannes Doerfert < johannesdoerfert at gmail.com >:
>>>
>>> Hi Kerim,
>>>
>>> I tried to help below. Looking at xeus-cling I did not immediately see
>>> why clang 5 is
>>> required. If this doesn't work as described below, I might spend time
>>> trying to get it
>>> to run with clang 11 ;)
>>>
>>> On 12/22/20 1:57 PM, Керим Хемраев via cfe-dev wrote:
>>>> Hi,
>>>>
>>>> I’m struggling with compiling simple OpenMP program with clang 5.0.0.
>>>> Here is the code (foo.cxx):
>>>>
>>>> #include   "omp.h"
>>>> #include   <stdio.h>
>>>> int   main ( void ) {
>>>>    #pragma   omp   parallel
>>>>    printf ( "thread %d \n " ,  omp_get_thread_num ());
>>>> }
>>>>
>>>> As I use clang as part of xeus-cling my clang installation is inside conda packages:
>>>> $ which clang
>>>> /home/tasik/miniconda3/envs/cling/bin/clang
>>>>
>>>> As this clang package does’t have omp.h I provide additional directories to find omp.h and libomp.so
>>>> To compile the code I use the command:
>>>> $ clang -fopenmp -I/home/../usr/lib/llvm-10/include/openmp/ -L/home/../usr/lib/llvm-10/lib foo.cxx
>>>>
>>>> And I get errors:
>>>> /usr/bin/ld: cannot find /lib64/libpthread.so.0
>>>> /usr/bin/ld: cannot find /usr/lib64/libpthread_nonshared.a
>>>> clang-5.0: error: linker command failed with exit code 1 (use -v to see invocation)
>>> The error basically means clang looks for the libthread libraries and
>>> cannot find them.
>>> Check on you system where they are and provide the path via -L to clang.
>>> That might allow
>>> you to proceed. That said, I don't think you are able to mix clang 5 and
>>> llvm 10 as you
>>> do now. The headers and libraries clang might pick up need to be
>>> consistent (with the clang
>>> version). At least, you need to make sure `omp.h` and `libomp.so` are
>>> the ones shipped with
>>> clang 5.
>>>
>>> ~ Johannes
>>>
>>>
>>>> I really need some help to undertand how to work with clang 5.0.0 OpenMP
>>>> And I think that it is difficult to update clang’s version as xeus-cling requires mentioned 5.0.0 version...
>>>>
>>>>
>>>> With respect,
>>>> kerim
>>>>
>>>> _______________________________________________
>>>> cfe-dev mailing list
>>>>  cfe-dev at lists.llvm.org
>>>>  https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>>
>> С уважением,
>> Керим Хемраев
>>  kerim.khemraev at mail.ru
>> 
 
 
С уважением,
Керим Хемраев
kerim.khemraev at mail.ru
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20201223/8fc676b7/attachment-0001.html>