Bug#791676: libmpich-dev 3.4~a2+really3.3.2-2 has broken Fortran due to gfortran-10 specific flags

[Drew Parsons]

On 2020-08-11 09:46, Drew Parsons wrote:
> Thanks Jed.  I think you're replying here in response to discussion
> raised elsewhere.  Could you provide a url link if its publicly
> accessible so we can catch the rest of the context?

Oh wait, I'm wrong aren't I?  Your reply is to Christian Engwer's 
question in Debian Bug#791676 
(https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=791676)

The glitch with mpifort a.f90 and gfortran-10/gfortran-9 might be a 
temporary problem.  We're still in the transition from gcc-9 to gcc-10.  
"mpifort a.f90" succeeds in debian unstable.  The problem here is that 
the gfortran package is 1.185.1 (defaulting to gcc-9) in debian testing, 
but 1.188 (gcc-10) in debian unstable.  The transition is held up by 
seqan, which is failing tests (see 
https://tracker.debian.org/pkg/gcc-defaults)

Since our default MPI is OpenMPI, we didn't catch the inconsistency in 
mpich soon enough. mpich 3.4~a2+really3.3.2-2 was recently built against 
gcc-10, but its gfortran dependency was not strict and so it migrated 
into debian testing ahead of gfortran (with the gfortran-10 default).

Drew