[petsc-users] ``--with-clanguage=c++" turns on "PETSC_HAVE_COMPLEX"?

[Balay, Satish]

On Fri, 3 May 2019, Fande Kong via petsc-users wrote:

> It looks like mpicxx from openmpi does not handle this correctly.

Perhaps my earlier messages was not clear. The problem is not with
OpenMPI - but your build of it. Its installed with 'clang' as the C++
compiler - it should be built with 'clang++' as the c++ compiler.

> I switched to mpich, and it works now.
> 
> However there is till some warnings:
> 
> *clang-6.0: warning: treating 'c' input as 'c++' when in C++ mode, this
> behavior is deprecated [-Wdeprecated]*
> *         CXX arch-linux2-c-opt-memory/obj/dm/impls/plex/glexg.o*
> *         CXX arch-linux2-c-opt-memory/obj/dm/impls/plex/petscpartmatpart.o*
> *clang-6.0: warning: treating 'c' input as 'c++' when in C++ mode, this
> behavior is dep*

Yes - because PETSc sources are in C - and you are building with
--with-clanguage=cxx - and this compiler thinks one should not compile
.c sources as c++.

Satish

> 
> Fande,
> 
> 
> On Fri, May 3, 2019 at 7:29 PM Balay, Satish <balay at mcs.anl.gov> wrote:
> 
> > >>>>>>>>
> > Executing: mpicxx -show
> >
> >                     stdout: clang
> > -I/Users/kongf/projects/openmpi-2.1.1_installed/include
> > -L/Users/kongf/projects/openmpi-2.1.1_installed/lib -lmpi
> > <<<<
> >
> > Hm - I think this [specifying a C compiler as c++] is the trigger of this
> > problem.
> >
> > configure checks if the c++ compiler supports complex. This test was
> > successful [as it was done with .cxx file - and presumably clang switches
> > to c++ mocd for a .cxx file.
> >
> > However PETSc sources a .c - so its likely compiling PETSc as C -  so
> > things are now inconsistant - and broken..
> >
> > Note:
> > PETSC_HAVE_COMPLEX => compilers support complex - so define a complex
> > datatype
> > PETSC_USE_COMPLEX => build PETSc with PetscScalar=complex
> >
> >
> > Satish
> >
> > On Fri, 3 May 2019, Fande Kong via petsc-users wrote:
> >
> > > Hi All,
> > >
> > > Comping PETSc with ``--with-clanguage=c"  works fine. But I could not
> > > compile PETSc with "--with-clanguage=c++" since the flag
> > > "PETSC_HAVE_COMPLEX" was wrongly set on by this option.
> > >
> > > */Users/kongf/projects/petsc/src/sys/objects/pinit.c:913:21: error:
> > > expected parameter declarator*
> > > *    PetscComplex ic(0.0,1.0);*
> > > *                    ^*
> > > */Users/kongf/projects/petsc/src/sys/objects/pinit.c:913:21: error:
> > > expected ')'*
> > > */Users/kongf/projects/petsc/src/sys/objects/pinit.c:913:20: note: to
> > match
> > > this '('*
> > > *    PetscComplex ic(0.0,1.0);*
> > > *                   ^*
> > > */Users/kongf/projects/petsc/src/sys/objects/pinit.c:914:13: error:
> > > assigning to 'PetscComplex' (aka '_Complex double') from incompatible
> > type
> > > 'PetscComplex ()' (aka '_Complex double ()')*
> > > *    PETSC_i = ic;*
> > > *            ^ ~~*
> > > *3 errors generated.*
> > > *make[2]: *** [arch-linux2-c-opt-memory/obj/sys/objects/pinit.o] Error 1*
> > > *make[2]: *** Waiting for unfinished jobs....*
> > > *make[2]: Leaving directory `/Users/kongf/projects/petsc'*
> > > *make[1]: *** [gnumake] Error 2*
> > > *make[1]: Leaving directory `/Users/kongf/projects/petsc'*
> > > ***************************ERROR**************************************
> > > *  Error during compile, check
> > > arch-linux2-c-opt-memory/lib/petsc/conf/make.log*
> > > *  Send it and arch-linux2-c-opt-memory/lib/petsc/conf/configure.log to
> > > petsc-maint at mcs.anl.gov <petsc-maint at mcs.anl.gov>*
> > > **********************************************************************
> > >
> > > The make and configure logs are attached.
> > >
> > > Fande,
> > >
> >
> >
>