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From: Brian Barrett (brbarret_at_[hidden])
Date: 2006-08-18 17:44:33

On Aug 18, 2006, at 3:19 PM, Hugh Merz wrote:

> On Fri, 18 Aug 2006, Steven A. DuChene wrote:
>> I am attempting to build OpenMPI-1.1 on a RHEL4u2 system that has
>> the standard gfortran install as part of the distro and with a
>> self installed
>> recent version of g95 from but when I use the FC flag to
>> configure to tell it where to find the g95 executable I get a message
>> during the configure run of
>> *** Fortran 90/95 compiler
>> checking whether we are using the GNU Fortran compiler... yes
>> checking whether /app/g95-newer/g95-install/bin/x86_64-unknown-
>> linux-gnu-g95 accepts -g... yes
>> checking if Fortran compiler works... yes
>> checking whether gfortran and /app/g95-newer/g95-install/bin/
>> x86_64-unknown-linux-gnu-g95 compilers are compatible... no
>> configure: WARNING: *** Fortran 77 and Fortran 90 compilers are
>> not link compatible
>> configure: WARNING: *** Disabling MPI Fortran 90/95 bindings
>> I am not specifying any particular FCFLAGS but from searching
>> through the mailing
>> lists I am pretty sure I should be but I just don't know what
>> exactly.
>> Any info on this anywhere?
> Compiler incompatibility is hinted at in this FAQ entry:
> Try setting the F77 environment variable to use g95 for Fortran 77
> compiler as well.
> If you don't need F77 bindings, then supply '--disable-f77' to
> configure and it should build fine.

Hugh is correct -- the issue is that you tried to use gfortran as the
Fortran 77 compiler and g95 as the Fortran 90 compiler. The Fortran
90 bindings are based on the Fortran 77, so the two compilers must be
link compatible. You can configure with both F77 and FC variables
set to either gfortran or g95 and all should be ok.

By the way, because the Fortran 90 bindings are layered on the
Fortran 77 bindings, supplying --disable-mpi-f77 to turn off the
Fortran 77 bindings will also disable the Fortran 90 bindings.