[petsc-dev] preprocessor for Fortran?

[Balay, Satish]

On Sun, 11 Aug 2019, Satish Balay wrote:

> On Sun, 11 Aug 2019, Smith, Barry F. via petsc-dev wrote:
> 
> > Matt and Satish,
> > 
> >   Years ago we had to sometimes use the C preprocessor for preprocessor  Fortran code. Isn't that no longer needed?
> 
> Don't remember when we removed this. Previously we needed this only for xlf - because it didn't support -D
> But then - we stopped using -D flags as part of the build. And when needed this for externalpackages - we
> use checkFortranDefineCompilerOption() to set the flag correctly for either ['-D', '-WF,-D']
> 
> > 
> > In FC.py there is 
> > 
> > class Preprocessor(config.compile.C.Preprocessor):
> >   '''The Fortran preprocessor, which now is just the C preprocessor'''
> >   def __init__(self, argDB):
> >     config.compile.C.Preprocessor.__init__(self, argDB)
> >     self.language        = 'FC'
> >     self.targetExtension = '.F90'
> >     self.includeDirectories = sets.Set()
> >     return
> > 
> > class Compiler(config.compile.processor.Processor):
> >   '''The Fortran compiler'''
> > 
> > 
> > which implies that C preprocessor is still handing around the Fortran. Now when all the Fortran compiler flags are generated with getFlags() it seems to include those from CPPFLAGS?
> > 
> > Is this correct now? I don't think it should be? Should there be a separate FCCPPFLAGS?  Bad things happen in the current situation when I set CPPFLAGS needed for clang but not for gfortran when MPICH is configured the CPPFLAGS are passed to the FCFLAGS which breaks things. 
> 
> I think things CPP was a bit central - and used with both Fortran and Cxx.
> 
> But at some point CXXPP and CXXPPFLAGS were added [but I'm not sure if it was correctly used.]
> 
> > 
> > I cannot find the exact line of code when the FFLAGS and CPPFLAGS are merged together for Fortran but I assume it is 
> 
> I see its in getPreprocessorFlagsName() in config/BuildSystem/config/base.py
> 
> > 
> >   def getFlags(self):
> >     '''Returns a string with the flags specified for running this processor.'''
> >     if not hasattr(self, '_flags'):
> >       flagsName = self.flagsName[:]
> >       if self.name == self.compiler.name:
> >         flagsName.extend(self.compiler.flagsName)
> >       if hasattr(self, 'configCompilers'):
> >         flags = ' '.join([getattr(self.configCompilers, name) for name in flagsName])
> >       else:
> >         flags = ' '.join([self.argDB[name] for name in flagsName])
> >       return flags
> >     return self._flags
> >   flags = property(getFlags, config.compile.processor.Processor.setFlags, doc = 'The flags for the executable')
> > 
> > 
> > How can this be fixed?
> 
> I pushed some changes to balay/add-FPPFLAGS branch. This appears to
> work for me. But its likely that I don't understand all the
> inter-dependencies between these options - so it might still be
> buggy..

Now these changes are at:

https://bitbucket.org/petsc/petsc/pull-requests/1962/configure-add-fppflags-and-not-use/diff

Satish