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

Alexey Bataev via cfe-dev cfe-dev at lists.llvm.org
Tue Dec 22 18:27:55 PST 2020 

Try to add this path to LIBRARY_PATH env var.

Best regards,
Alexey Bataev

22 дек. 2020 г., в 21:22, Керим Хемраев via cfe-dev <cfe-dev at lists.llvm.org> написал(а):


Thank you very much!

I’ve figured out that I have libpthread.so.0 in /usr/lib/x86_64-linux-gnu

So I can compile it with command:
$ clang++ -fopenmp foo.cxx -I/home/../usr/lib/llvm-10/include/openmp/ -L/home/../usr/lib/llvm-10/lib -L/home/../usr/lib/x86_64-linux-gnu

Is there a way to change that /usr/bin/ld looks for libpthread.so.0 in /usr/lib/x86_64-linux-gnu instead of /lib64 ?

Среда, 23 декабря 2020, 5:13 +03:00 от Johannes Doerfert <johannesdoerfert at gmail.com>:

Maybe install libpthread-dev?


On 12/22/20 8:07 PM, Керим Хемраев wrote:
> Yes, it is
>
> The command:
>
> $ clang++ -fopenmp foo.cxx -I/home/../usr/lib/llvm-10/include/openmp/ -L/home/../usr/lib/llvm-10/lib
>
> gives the error:
> /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)
>
>
>
>> Среда, 23 декабря 2020, 5:02 +03:00 от Johannes Doerfert <johannesdoerfert at gmail.com</compose?To=johannesdoerfert at gmail.com>>:
>>
>> Ok, closer. is there a symlink from libomp.so to libomp.so.5 in
>> /home/../usr/lib/llvm-10/lib ?
>> If not, create one. Then try:
>>
>> clang++ -fopenmp foo.cxx -I/home/../usr/lib/llvm-10/include/openmp/ -L/home/../usr/lib/llvm-10/lib
>>
>>
>>
>> On 12/22/20 8:00 PM, Керим Хемраев wrote:
>>> $ clang++ -fopenmp foo.cxx
>>>
>>> gives:
>>> foo.cxx:2:10: fatal error: 'omp.h' file not found
>>> #include "omp.h"
>>>          ^~~~~~~
>>> 1 error generated.
>>>
>>>
>>> Then I try:
>>>
>>> $ clang++ -fopenmp foo.cxx -I/home/../usr/lib/llvm-10/include/openmp/
>>>
>>> this produces the error:
>>> /usr/bin/ld: cannot find -lomp
>>> clang-5.0: error: linker command failed with exit code 1 (use -v to see invocation)
>>>
>>> The dir:  -I/home/../usr/lib/llvm-10/include/openmp/ contains omp.h
>>>
>>>> Среда, 23 декабря 2020, 4:56 +03:00 от Johannes Doerfert < johannesdoerfert at gmail.com</compose?To=johannesdoerfert at gmail.com> >:
>>>>
>>>> -fopenmp will add the -lomp, which will look for libomp.so in your
>>>> library path.
>>>>
>>>> Again, libomp.so versioning is not related to clang versioning.
>>>>
>>>> What is the output of
>>>>
>>>> clang++ -fopenmp foo.cxx
>>>>
>>>>
>>>>
>>>> On 12/22/20 7:33 PM, Керим Хемраев wrote:
>>>>> It seems I know where is my fault (it
>>>>>
>>>>>
>>>>> using clang 5.0 with libomp.so.5 is probably not going to work.
>>>>>
>>>>> is was very obvious) but I can’t understand how can I link external library to clang.
>>>>>
>>>>> In the folder  /home/../usr/lib/llvm-10/lib I have a file called  libomp.so.5 (as I understood it is a library of version 5)   and I strongly believe that I need to link this library when parsing commands to clang++:
>>>>>
>>>>> $ clang++ -fopenmp foo.cxx -I/home/../usr/lib/llvm-10/include/openmp/ -L/home/../usr/lib/llvm-10/lib libomp.so.5
>>>>>
>>>>> gives me error:
>>>>> clang-5.0: error: no such file or directory: 'libomp.so.5'
>>>>>
>>>>> How to link  libomp.so.5 ? Can’t find it in google yet
>>>>>
>>>>>
>>>>>> Среда, 23 декабря 2020, 2:33 +03:00 от Johannes Doerfert < johannesdoerfert at gmail.com</compose?To=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</compose?To=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</compose?To=cfe%2ddev at lists.llvm.org>
>>>>>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>> С уважением,
>>>>>>> Керим Хемраев
>>>>>>> kerim.khemraev at mail.ru</compose?To=kerim.khemraev at mail.ru>
>>>>>>>
>>>>> С уважением,
>>>>> Керим Хемраев
>>>>> kerim.khemraev at mail.ru</compose?To=kerim.khemraev at mail.ru>
>>>>>
>>>
>>> С уважением,
>>> Керим Хемраев
>>> kerim.khemraev at mail.ru</compose?To=kerim.khemraev at mail.ru>
>>>
>
>
> С уважением,
> Керим Хемраев
> kerim.khemraev at mail.ru</compose?To=kerim.khemraev at mail.ru>
>


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

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