Index: gcc/fortran/interface.c
===================================================================
*** gcc/fortran/interface.c	(revision 114148)
--- gcc/fortran/interface.c	(working copy)
*************** compare_parameter (gfc_symbol * formal, 
*** 1123,1129 ****
  	  && !compare_type_rank (formal, actual->symtree->n.sym))
  	return 0;
  
!       if (formal->attr.if_source == IFSRC_UNKNOWN)
  	return 1;		/* Assume match */
  
        return compare_interfaces (formal, actual->symtree->n.sym, 0);
--- 1123,1130 ----
  	  && !compare_type_rank (formal, actual->symtree->n.sym))
  	return 0;
  
!       if (formal->attr.if_source == IFSRC_UNKNOWN
! 	    || actual->symtree->n.sym->attr.external)
  	return 1;		/* Assume match */
  
        return compare_interfaces (formal, actual->symtree->n.sym, 0);
*************** compare_actual_formal (gfc_actual_arglis
*** 1177,1182 ****
--- 1178,1184 ----
  {
    gfc_actual_arglist **new, *a, *actual, temp;
    gfc_formal_arglist *f;
+   gfc_gsymbol *gsym;
    int i, n, na;
    bool rank_check;
  
*************** compare_actual_formal (gfc_actual_arglis
*** 1276,1281 ****
--- 1278,1301 ----
  	  return 0;
  	}
  
+       /* Satisfy 12.4.1.2 by ensuring that a procedure actual argument is
+ 	 provided for a procedure formal argument.  */
+       if (a->expr->ts.type != BT_PROCEDURE
+ 	  && a->expr->expr_type == EXPR_VARIABLE
+ 	  && f->sym->attr.flavor == FL_PROCEDURE)
+ 	{
+ 	  gsym = gfc_find_gsymbol (gfc_gsym_root,
+ 				   a->expr->symtree->n.sym->name);
+ 	  if (gsym == NULL || (gsym->type != GSYM_FUNCTION
+ 		&& gsym->type != GSYM_SUBROUTINE))
+ 	    {
+ 	      if (where)
+ 		gfc_error ("Expected a procedure for argument '%s' at %L",
+ 			   f->sym->name, &a->expr->where);
+ 	      return 0;
+ 	    }
+ 	}
+ 
        if (f->sym->as
  	  && f->sym->as->type == AS_ASSUMED_SHAPE
  	  && a->expr->expr_type == EXPR_VARIABLE
Index: gcc/testsuite/gfortran.dg/dummy_procedure_1.f90
===================================================================
*** gcc/testsuite/gfortran.dg/dummy_procedure_1.f90	(revision 0)
--- gcc/testsuite/gfortran.dg/dummy_procedure_1.f90	(revision 0)
***************
*** 0 ****
--- 1,47 ----
+ ! { dg-do compile }
+ ! Test the patch for PR25098, where passing a variable as an
+ ! actual argument to a formal argument that is a procedure
+ ! went undiagnosed.
+ !
+ ! Based on contribution by Joost VandeVondele  <jv244@cam.ac.uk>
+ !
+ integer function y()
+   y = 1
+ end
+ integer function z()
+   z = 1
+ end
+ 
+ module m1
+ contains
+   subroutine s1(f)
+     interface
+       function f()
+         integer f
+       end function f
+     end interface
+   end subroutine s1
+ end module m1
+ 
+   use m1
+   external y
+   interface
+    function x()
+      integer x
+    end function x
+   end interface
+ 
+   integer :: i, y, z
+   i=1
+   call s1(i) ! { dg-error "Expected a procedure for argument" }
+   call s1(w) ! { dg-error "not allowed as an actual argument" }
+   call s1(x) ! explicit interface
+   call s1(y) ! declared external
+   call s1(z) ! already compiled
+ contains
+   integer function w()
+     w = 1
+   end function w
+ end
+ 
+ ! { dg-final { cleanup-modules "m1" } }
Index: gcc/testsuite/gfortran.dg/dummy_procedure_2.f90
===================================================================
*** gcc/testsuite/gfortran.dg/dummy_procedure_2.f90	(revision 0)
--- gcc/testsuite/gfortran.dg/dummy_procedure_2.f90	(revision 0)
***************
*** 0 ****
--- 1,33 ----
+ ! { dg-do compile }
+ ! Checks the fix for the bug exposed in fixing PR25147
+ !
+ ! Contributed by Tobias Schlueter  <tobi@gcc.gnu.org>
+ !
+ module integrator
+   interface
+      function integrate(f,xmin,xmax)
+        implicit none
+        interface
+           function f(x)
+             real(8) :: f,x
+             intent(in) :: x
+           end function f
+        end interface
+        real(8) :: xmin, xmax, integrate
+      end function integrate
+   end interface
+ end module integrator
+ 
+   use integrator
+   call foo1 ()
+   call foo2 ()
+ contains
+   subroutine foo1 ()
+     real(8) :: f                   ! This was not trapped: PR25147/25098
+     print *,integrate (f,0d0,3d0) ! { dg-error "Expected a procedure" }
+   end subroutine foo1
+   subroutine foo2 ()
+     real(8), external :: g ! This would give an error, incorrectly.
+     print *,integrate (g,0d0,3d0)
+   end subroutine foo2
+ end