On Feb 7, 2008, at 7:03 PM, Adam C Powell IV wrote:
But then, why wouldn't programs expect to be able to include C headers
in a C++ extern C block?
But that's exactly the issue: mpi.h is not a C header. It is mandated
by the MPI standard to be both a C and a C++ header file. We (Open
MPI) can't change the filename or the languages where it can be used.
Or rather, why shouldn't they be able to do so
with mpi.h -- or hdf5.h, which isn't mpi.h
Both mpi.h and hdf5.h do the right things with regards to extern
"C" {}. So they are C++-safe.
-- when numerous other C
header files allow it, possibly including other MPI implementations?
Are you sure of that? It is my [possibly flawed] understanding that
HDF5 can be compiled with or without MPI support. If that is right,
it is therefore possible that Salome has been developed/tested/used
with serial HDF5, and this issue never came up.
Can you get Salome to compile with an HDF5 that was built with support
for another MPI implementation?
After all, it's called mpi.h not mpi.hh or .hxx or mpi_cxx.h, right?
And isn't the patched version cleaner, in that it separates the C and
C++ prototypes into different #ifdef/#define regions?
My objection to your patch is twofold:
1. OMPI is not doing anything wrong, and I'm reluctant to "fix"
something that is not wrong without a very good reason. To be blunt:
one open source application that is coded wrong (and can easily be
fixed) is not a very good reason, IMHO.
2. Your patch still requires the application to use an OMPI-specific
#define. That doesn't seem like a good idea.
Put differently: from your description, Salome is a non-conformant MPI
application and therefore may or may not work with any given MPI.
Instead of having each MPI that Salome (HDF5) fails to compile with
provide a workaround, the [much] more portable solution is to have
Salome fix their #includes. This will allow Salome to compile against
any MPI implementation.
I'm clearly not the only OMPI developer, though, so if the community
decides to accept your patch, I certainly won't prevent anyone from
doing so. These are just my opinions. :-)
Have you talked to the Salome developers? Wouldn't an upstream fix
alleviate the need for you to put in an Open MPI-specific patch (or
any patch at all)? Alternatively, have you talked to the HDF5
maintainers to see if they can remove <mpi.h> from their public header
files?
--
Jeff Squyres
Cisco Systems
