[Dune-devel] Building dune-common with gcc-4.8 fails

[Christian Engwer]

Hi Carsten,

I can confirm this behaviour for debian testing.

The problem seems to be inherent to mpich, as the mpicc.mpich always
uses these flags, regardless of the chosen compiler, this

mpicc -cc=/usr/bin/gcc-4.8 ...

will results in the same problem.

I think we have to work around this. How about just removing all
"-f..." options from MPI flags?

Christian

On Wed, Jul 01, 2015 at 10:20:57PM +0200, Carsten Gräser wrote:
> Am 01.07.2015 um 15:50 schrieb Carsten Gräser:
> > Am 01.07.2015 um 15:40 schrieb Jö Fahlke:
> >> Am Wed,  1. Jul 2015, 15:35:12 +0200 schrieb Carsten Gräser:
> >>> Date: Wed, 01 Jul 2015 15:35:12 +0200
> >>> From: Carsten Gräser <graeser at mi.fu-berlin.de>
> >>> To: "dune-devel at dune-project.org" <dune-devel at dune-project.org>
> >>> Subject: Re: [Dune-devel] Building dune-common with gcc-4.8 fails
> >>>
> >>> Hi Jö,
> >>
> >>> CMakeCache shows that this flag is also present in MPI_CXX_COMPILE_FLAGS
> >>> and MPI_C_COMPILE_FLAGS.
> >>
> >> In your other Mail you bisected the problem to the patch that enabled mpi by
> >> default in cmake.  So this sounds very mpi-related.  Maybe that flag is
> >> extracted from mpicc?  And you don't have a problem before the patch because
> >> dune-common did not look for mpi then, but is doing it now?
> >>
> >> Which MPI are you using?
> > It's mpich-3.1.
> > 
> > I also noticed that passing the compiler to mpic++ via -cxx preserves
> > this -fstack-protector-strong option which seems to be the ubuntu default.
> 
> I guess I've found the origin of the problem, but I don't now
> who's to blame and how to fix this: Recent Ubuntu decided to enable
> 
>   -D_FORTIFY_SOURCE=2  -fstack-protector-strong
> 
> by default for security reasons. This also seems to imply that these
> flags are by default used with the mpi compiler wrappers, at least
> according to
> 
>   mpicxx -show
> 
> Not surprisingly the cmake module FindMPI detects these flags and
> stores them in MPI_C_COMPILER_FLAGS which we forwarded to
> MPI_DUNE_COMPILE_FLAGS and thus use when building dune
> applications with mpi. The problem is that the second flag is
> not supported with gcc versions < 4.9, but the flag is always passed.
> It's a little unclear, who is to blame for this problem:
> 
> a)Dune is blindly passing the mpi compile flags regardless of the
>   selected compiler.
> 
> b)FindMPI does not allow to pass a compiler in order to detect
>   suitable flags.
> 
> c)Even "mpicc -cc=/usr/bin/gcc-4.8" does not provide suitable flags.
> 
> d)Is it a ubuntu bug to always provide these flags with mpi,
>   regardless of the compiler?
> 
> I'd like to at least circumvent the problem to be able to test
> with all my compilers, but it seems that one cannot overwrite
> the MPI_C_COMPILER_FLAGS with a command line argument.
> For now I have to manually remove the flag in the cache
> if I want to test with a packaged but older compiler. Does
> anybody more familiar with mpi and cmake now a better way
> to get around this?
> 
> Best,
> Carsten
> 
> 



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-- 
Prof. Dr. Christian Engwer 
Institut für Numerische und Angewandte Mathematik
Fachbereich Mathematik und Informatik der Universität Münster
Einsteinstrasse 62
48149 Münster

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