[lustre-discuss] Compile a C++ app. using the Lustre API

François Tessier ftessier at anl.gov
Thu Mar 16 08:11:52 PDT 2017 

Here is the workaround I found (based on static_cast<>()):

- make a local copy of lustre_user.h and lustreapi.h
- apply the attached patch on lustre_user.h
- add an include parameter in your CXXFLAGS pointing to these files
- compile with CC

It's clearly not the best solution but it's a working temporary band-aid...

++

François


On 03/16/2017 07:44 AM, François Tessier wrote:
> On 03/15/2017 05:50 PM, Dilger, Andreas wrote:
>> On Mar 15, 2017, at 15:22, François Tessier <ftessier at anl.gov> wrote:
>>> I get the same errors with g++ (v. 6.3). I can't find what kind of compiler flag I can use to be able to compile this. It clearly comes from how C++ deals with enum. The solutions I've found consist in "static_casting" the int values... Modifying my local version of lustre_user.h is probably not the best idea :-)
>> Have you tried adding the standard wrappers at the start and end of the lustre_user.h header:
>>
>> #ifdef __cplusplus
>> extern "C" {
>> #endif
>> :
>> <rest of header>
>> #ifdef __cplusplus
>> }
>> #endif
>>
>> I thought we had added those long ago, but I don't see them in the header today.  If that fixes your problem, please file an LU ticket at https://jira.hpdd.intel.com/ (and ideally a patch at https://review.whamcloud.com/ too) and we can get this added to the header.
>>
>> In the meantime, you could also wrap your "#include <lustre/lustre_user.h>" similarly.
> It doesn't fix the problem. I tried a more recent version of g++ or
> several compiler options to force the use of C++11 [1] but with no success.
>> Cheers, Andreas
> Cheers,
> François
>
> [1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2347.pdf
>>> On 03/15/2017 02:14 PM, Patrick Farrell wrote:
>>>> It looks like your compiler is being fussier than the C compiler.
>>>>
>>>> Specifically, the problem appears to be with the enum type.  The C compiler is happy to let pass using a short (cr_flags) where an enum is called for (argument to changelog_rec_offset).  In C, I think an enum is an int (so passing in a short like this is always fine).  I guess in C++ either enum is not an int, or it's just fussier.
>>>>
>>>> There might be a compiler flag to make it not error on this?  I am not familiar with icpc, so I can't help with specifics.
>>>>
>>>> You might also try a different C++ compiler, to see if it has a different attitude towards that error.
>>>>
>>>> One further thought, though:
>>>> This is a C header.  Presumably, it is not intended to be included directly in a C++ project?
>>>>
>>>> - Patrick
>>>> From: lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on behalf of François Tessier <ftessier at anl.gov>
>>>> Sent: Wednesday, March 15, 2017 2:00:31 PM
>>>> To: lustre-discuss at lists.lustre.org
>>>> Subject: [lustre-discuss] Compile a C++ app. using the Lustre API
>>>>  
>>>> Hi All,
>>>>
>>>> I'm working on a piece of code using the Lustre API. To do so, I include
>>>> lustreapi.h. When I compile my code with a C compiler (icc), everything
>>>> is fine. However, when I compile it with a C++ compiler (icpc), I get
>>>> these errors:
>>>>
>>>> ---------------------------------
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(914): error: argument of type "__u16={unsigned short}" is incompatible with parameter of type "changelog_rec_flags"
>>>>          return changelog_rec_offset(rec->cr_flags);
>>>>                                      ^
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(925): error: a value of type "int" cannot be used to initialize an entity of type "changelog_rec_flags"
>>>>          enum changelog_rec_flags crf = rec->cr_flags & CLF_VERSION;
>>>>                                         ^
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(935): error: a value of type "int" cannot be used to initialize an entity of type "changelog_rec_flags"
>>>>          enum changelog_rec_flags crf = rec->cr_flags &
>>>>                                         ^
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(945): error: argument of type "int" is incompatible with parameter of type "changelog_rec_flags"
>>>>          return (char *)rec + changelog_rec_offset(rec->cr_flags &
>>>>                                                    ^
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(986): error: this operation on an enumerated type requires an applicable user-defined operator function
>>>>          crf_wanted &= CLF_SUPPORTED;
>>>>                     ^
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(997): error: argument of type "int" is incompatible with parameter of type "changelog_rec_flags"
>>>>                    changelog_rec_offset(crf_wanted & ~CLF_JOBID);
>>>>                                         ^
>>>>
>>>> In file included from /usr/include/lustre/lustreapi.h(47),
>>>>                  from topo.c(5):
>>>> /usr/include/lustre/lustre_user.h(999): error: argument of type "int" is incompatible with parameter of type "changelog_rec_flags"
>>>>                    changelog_rec_offset(crf_wanted & ~(CLF_JOBID | CLF_RENAME));
>>>>                                         ^
>>>>
>>>> Makefile:10: recipe for target 'topo' failed
>>>> make: *** [topo] Error 2
>>>>
>>>> ---------------------------------
>>>>
>>>> It's probably more a compiler issue than a Lustre one but a solution
>>>> could help other users or Lustre developers.
>>>>
>>>> Any idea?
>>>>
>>>> Thanks,
>>>>
>>>> François
>>>>
>>>>
>>>> -- 
>>>> --
>>>> François TESSIER, Ph.D.
>>>> Postdoctoral Appointee
>>>> Argonne National Laboratory
>>>> LCF Division - Bldg 240, 4E 19
>>>> Tel : +1 (630)-252-5068
>>>> http://www.francoistessier.info
>>>>
>>>> _______________________________________________
>>>> lustre-discuss mailing list
>>>> lustre-discuss at lists.lustre.org
>>>> http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
>>> _______________________________________________
>>> lustre-discuss mailing list
>>> lustre-discuss at lists.lustre.org
>>> http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
>> Cheers, Andreas
>> --
>> Andreas Dilger
>> Lustre Principal Architect
>> Intel Corporation
>>
>>
>>
>>
>>
>>
>>
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