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

Tue Dec 22 16:08:44 PST 2020

Thank you!
The command:
$  clang++-10 -fopenmp foo.cxx

successfully builds. 
$  ./a.out
thread 1
thread 2
thread 0
thread 3

Now I think we can go back to xeus-cling :)

>Среда, 23 декабря 2020, 2:57 +03:00 от Johannes Doerfert <johannesdoerfert at gmail.com>:
> 
>clang++-10 -fopenmp foo.cxx  (or whatever the clang++ symlink is called)
>
>~ Johannes
>
>
>On 12/22/20 5:37 PM, Керим Хемраев wrote:
>> 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
>>

С уважением,
Керим Хемраев
kerim.khemraev at mail.ru

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