https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91556
--- Comment #19 from anlauf at gcc dot gnu.org --- (In reply to Thomas Koenig from comment #18) > (In reply to anlauf from comment #14) > > The current solution is a bit annoying for implicitly-derived interfaces. > > > > Consider a code like: > > > > module foo > > implicit none > > type t1 > > integer :: i = 1 > > end type t1 > > type t2 > > integer :: j = 2 > > end type t2 > > contains > > subroutine s1 (x) > > type(t1) :: x > > call my_mpi_bcast_wrapper (x, storage_size (x)/8) > > end subroutine s1 > > subroutine s2 (y) > > type(t2) :: y > > call my_mpi_bcast_wrapper (y, storage_size (y)/8) > > end subroutine s2 > > end module foo > > > > That's perfectly legal, > > This is illegal, as far as I know. The type names are different, > which makes them different types. Of course the types are different - that's the point! The above is an attempt to extract a self-contained example demonstrating what does happen in real-world codes using MPI. You can convert it to the real thing yourself (see e.g. man mpi_bcast). What I wanted to say: in many codes using MPI, the 'buffer' argument of MPI_* can be of any type or kind, provided the other arguments are appropriately set. There is no explicit interface - the library routines may not even be written in Fortran - and there cannot be any reasonable inference from an implicit interface. Using this to generate an error *by default* is not a good idea. The same problem shows up for me in parts of the code using direct calls to BLAS (again, no explicit interfaces), or to NetCDF. I guess this is similar to the issues people reported for the SPEC codes. The recommendation to use -fallow-argument-mismatch to downgrade this to a warning (not silence it!) does not really solve the issue: the signal-to-noise ratio of gfortran warnings has become close to useless. (Just ask colleagues whether they pay attention to warnings.) And do you really want users to add -w to the list of options? If you think about it, you might conclude that this will do gfortran a poor service. I'll stop ranting now.
