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

Tue Mar 23 14:42:40 CDT 2021

On Tue, Mar 23, 2021 at 1:15 PM Junchao Zhang <junchao.zhang at gmail.com>
wrote:

> Can we combine CXXPPFLAGS and CXXFLAGS into one CXXFLAGS?
>

No. There are compiler-only flags.

  Matt

> --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
>>> > > >
>>> > > >
>>> > > >
>>> > >
>>> > >
>>> >
>>>
>>>
>>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20210323/c146c085/attachment.html>