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 <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 <[email protected]>: > > 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 <[email protected] > <mailto:[email protected]>> 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 < > > [email protected] <mailto:[email protected]>> 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 > > > > > > <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 > > > > > > > > > > > > > > > > > > > > >
