> a missing ierr can be a common cause for a segv in Fortran -- we
> typically don't assign to ierr until after the MPI_Send completes, so
> it *could* explain the behavior you're seeing...?
that was indeed the problem, I'm an idiot (sorry...). I thought there
was an explicit interface somewhere in the libraries that would signal
a missing argument as a syntax error, so I did not check as carefully
as I should have...
thanks to everybody for helping, hope the next time I'll have
something less stupid to ask...