Procedure must have an explicit interface specified

Question

hello all,
i'm facing a problem i don't understand. Here is a piece of code that compiles well with gfortran, but not on sun studio:
program test_fortran
  implicit none
  interface
     subroutine f1(t)
       double precision, intent(in), dimension(:,:) :: t
     end subroutine f1
     subroutine f2(t)
       double precision, intent(in), dimension(:,:) :: t
     end subroutine f2
     subroutine fct()
     end subroutine fct
  end interface
  call fct()
end program test_fortran
subroutine f1(t)
  double precision, intent(in), dimension(:,:) :: t
  print *, 'f1'
end subroutine f1
subroutine f2(t)
  double precision, intent(in), dimension(:,:) :: t
  print *, 'f2'
end subroutine f2
subroutine fct()
  double precision, allocatable, dimension(:,:) :: t
  allocate (t(5,5))
  call f1(t)
  call f2(t)
  deallocate(t)
end subroutine fctand f90 (SS12u1) gives me errors:
nemo-henry% f90 test_fortran.f90
  call f1(t)
  ^         
"test_fortran.f90", Line = 37, Column = 3: ERROR: Procedure "F1" is defined at line 21 (test_fortran.f90).  It must have an explicit interface specified.
  call f2(t)
  ^         
"test_fortran.f90", Line = 38, Column = 3: ERROR: Procedure "F2" is defined at line 27 (test_fortran.f90).  It must have an explicit interface specified.
f90comp: 43 SOURCE LINES
f90comp: 2 ERRORS, 0 WARNINGS, 0 OTHER MESSAGES, 0 ANSIAnybody can help?
thanks in advance,
gerard

Answer 1

The Fortran 99, 95, and 2003 standards require a procedure that
has one or more assumed-shape dummy arguments to have
explicit interface in any scoping unit in which it appears. In
your example, the subroutines f1 and f2 have explicit
interface in the main prgram, but they have implicit interface in
the subroutine fct. You need to provide explicit interface for
f1 and f2 in fct. You might want in copy the interface block
that appears in the main program in fct.
Sun Fortran keeps a record of the interfaces of the program units
it encounters. That is why it knows f1 and f2 need to have
explicit interfaces in fct. If you move the text of f1 and f2 so
that they appear after fct, the error message is likely to go away.
The code will be broken, but you will not get an error message.
Bob Corbett