[petsc-dev] configureLibrary fails for c++11 projects

[Junchao Zhang]

Can we combine CXXPPFLAGS and CXXFLAGS into one CXXFLAGS?
--Junchao Zhang


On Tue, Mar 23, 2021 at 11:38 AM Patrick Sanan <patrick.sanan at gmail.com>
wrote:

> I had a related (I think) issue trying to build with Kokkos. Those headers
> throw an #error if they're expecting OpenMP and the compiler doesn't have
> the OpenMP flag. I have an open MR here (number 60^2!) which thus adds the
> OpenMP flag to the CXXPPFLAGS:
> https://gitlab.com/petsc/petsc/-/merge_requests/3600
>
>
> My collaborator at CSCS was testing with the latest Kokkos and ran into an
> even hairier version of this problem trying to use CUDA - the Kokkos
> headers now apparently check that you're using nvcc. He has some workaround
> which I'll review and hopefully be able to submit.
>
>
> Am 23.03.2021 um 17:04 schrieb Stefano Zampini <stefano.zampini at gmail.com
> >:
>
> The check fails within buildsystem when running mpicc -E (which uses
> CXXPPFLAGS)  The package header needs c++11  to be included properly.
> C++11 is also needed at preprocessing time
>
> Il Mar 23 Mar 2021, 18:59 Satish Balay <balay at mcs.anl.gov> ha scritto:
>
>> -std=cxx11 for sure is a compile flag. But don't really know if its
>> also needed at pre-process stage and/or at link stage.
>>
>> And for compile stage both CXXFLAGS and CXXPPFLAGS should get
>> used. [PETSc makefiles make sure this is the case]
>>
>> And for link stage CXXFLAGS and LDFLAGS get used [but then sometimes
>> we have CLINKER, and FLINKER - and they certainly don't use CXXFLAGS -
>> so -std=cxx11 isn't really needed at link time?
>>
>> So the previous default of CXXPPFLAGS=-std=cxx11 looks reasonable to me.
>>
>> However if this project is not using PETSc makefiles - it should make
>> sure all compile flags are grabbed.
>>
>> # lib/petsc/conf/variables
>> PETSC_CXXCPPFLAGS       = ${PETSC_CC_INCLUDES} ${PETSCFLAGS}
>> ${CXXPP_FLAGS} ${CXXPPFLAGS}
>> CXXCPPFLAGS             = ${PETSC_CXXCPPFLAGS}
>> PETSC_CXXCOMPILE_SINGLE = ${CXX} -o $*.o -c ${CXX_FLAGS} ${CXXFLAGS}
>> ${CXXCPPFLAGS}
>>
>> # lib/petsc/conf/rules
>> .cpp.o .cxx.o .cc.o .C.o:
>>         ${PETSC_CXXCOMPILE_SINGLE} `pwd`/$<
>>
>> # gmakefile.test
>> PETSC_COMPILE.cxx = $(call quiet,CXX) -c $(CXX_FLAGS) $(CXXFLAGS)
>> $(CXXCPPFLAGS) $(CXX_DEPFLAGS)
>>
>> # lib/petsc/conf/test
>> LINK.cc = $(CXXLINKER) $(CXX_FLAGS) $(CXXFLAGS) $(CXXCPPFLAGS) $(LDFLAGS)
>>
>> Satish
>>
>>
>> On Tue, 23 Mar 2021, Junchao Zhang wrote:
>>
>> > I would rather directly change the project to use CXXFLAGS instead of
>> > CXXPPFLAGS.
>> >
>> > --Junchao Zhang
>> >
>> >
>> > On Tue, Mar 23, 2021 at 10:01 AM Satish Balay via petsc-dev <
>> > petsc-dev at mcs.anl.gov> wrote:
>> >
>> > > On Tue, 23 Mar 2021, Stefano Zampini wrote:
>> > >
>> > > > Just tried out of main, and and the include tests of a c++11
>> project fail
>> > > > Below my fix, if we agree on, I'll make a MR
>> > > >
>> > > > diff --git a/config/BuildSystem/config/compilers.py
>> > > > b/config/BuildSystem/config/compilers.py
>> > > > index c96967e..44e4657 100644
>> > > > --- a/config/BuildSystem/config/compilers.py
>> > > > +++ b/config/BuildSystem/config/compilers.py
>> > > > @@ -527,6 +527,8 @@ class Configure(config.base.Configure):
>> > > >          if self.setCompilers.checkCompilerFlag(flag, includes,
>> > > > body+body14):
>> > > >            newflag = getattr(self.setCompilers,LANG+'FLAGS') + ' ' +
>> > > flag #
>> > > > append flag to the old
>> > > >            setattr(self.setCompilers,LANG+'FLAGS',newflag)
>> > > > +          newflag = getattr(self.setCompilers,LANG+'PPFLAGS') + '
>> ' +
>> > > flag
>> > > > # append flag to the old
>> > > > +          setattr(self.setCompilers,LANG+'PPFLAGS',newflag)
>> > >
>> > >
>> > >
>> https://gitlab.com/petsc/petsc/commit/ead1aa4045d7bca177e78933b9ca25145fc3c574
>> > >
>> > >           self.setCompilers.CXXPPFLAGS += ' ' + flag
>> > >           newflag = getattr(self.setCompilers,LANG+'FLAGS') + ' ' +
>> flag #
>> > > append flag to the old
>> > >           setattr(self.setCompilers,LANG+'FLAGS',newflag)
>> > >
>> > > So the old code was setting 'PPFLAGS' - but this commit changed to
>> > > 'FLAGS'. Maybe this flag is needed at both compile time and link time?
>> > >
>> > > So this project is somehow using CXXPPFLAGS - but not CXXFLAGS?
>> > >
>> > > I'm fine with adding it to PPFLAGS - duplicate listing hopefully
>> shouldn't
>> > > cause grief.
>> > >
>> > > Satish
>> > >
>> > > >            cxxdialect = 'C++14'
>> > > >            self.addDefine('HAVE_'+LANG+'_DIALECT_CXX14',1)
>> > > >            self.addDefine('HAVE_'+LANG+'_DIALECT_CXX11',1)
>> > > > @@ -546,6 +548,8 @@ class Configure(config.base.Configure):
>> > > >          if self.setCompilers.checkCompilerFlag(flag, includes,
>> body):
>> > > >            newflag = getattr(self.setCompilers,LANG+'FLAGS') + ' ' +
>> > > flag #
>> > > > append flag to the old
>> > > >            setattr(self.setCompilers,LANG+'FLAGS',newflag)
>> > > > +          newflag = getattr(self.setCompilers,LANG+'PPFLAGS') + '
>> ' +
>> > > flag
>> > > > # append flag to the old
>> > > > +          setattr(self.setCompilers,LANG+'PPFLAGS',newflag)
>> > > >            cxxdialect = 'C++11'
>> > > >            self.addDefine('HAVE_'+LANG+'_DIALECT_CXX11',1)
>> > > >            break
>> > > >
>> > > >
>> > > >
>> > >
>> > >
>> >
>>
>>
>
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