Bugs of IVF compiler?

[Zhanghong_T_]

Dear all,

I have the following code which will crash when compiled without /warn:interfaces option, but no any problem if have the /warn:interfaces option. Is there any bug of IVF compiler, or any problem in my code? How should I modify the code to let the pointer to be passed to a subroutine?

Thanks,
Zhanghong Tang

[bash]!  test_mp.f90 
!
!  FUNCTIONS:
!  test_mp - Entry point of console application.
!

!****************************************************************************
!
!  PROGRAM: test_mp
!
!  PURPOSE:  Entry point for the console application.
!
!****************************************************************************
module element
  type pointp
    integer,pointer::p = > null()
  endtype

endmodule

    program test_mp
    use element

    implicit none

    ! Variables
    type(pointp),pointer::pp
    allocate(pp)
     ! read model size and resistivity parameter
    call testpp(pp)
    ! Body of test_mp
    print *, 'Hello World'

    end program test_mp

    subroutine testpp(pp)
    use element
    implicit none
    type(pointp),pointer::pp
    if(associated(pp%p))then
      write(*,*)1
    endif
    end subroutine
[/bash]

[Steven_L_Intel1]

It is your program that has the bug. Which compiler version are you using? When I compile with /warn:interfaces, I get this:

t.f90(17): warning #8055: The procedure has a dummy argument that has the ALLOCATABLE, ASYNCHRONOUS, OPTIONAL, POINTER, TARGET, VALUE or VOLATILE attribute. Required explicit interface is missing from original source. [PP]
call testpp(pp)
----------------^

As the error says, you are calling a procedure that has a dummy argument (PP) with the POINTER attribute. This requires that an explicit interface be visible to the caller, and you do not. If you put testpp in module element, that would be sufficient. Or testpp could be a CONTAINed routine of the main program.

[Zhanghong_T_]

Dear Dr. Steve,

Thank you very much for your kindly reply. I also noticed this warning, and also noticed that if I put the subroutine inside the module, everything is OK. But I don't understand that if the argument has some other attributes such as integer, there is no any problem. So I think that it's better to take ALL types of argument the same: require explicit interface or not.


Thanks,
Zhanghong Tang

[Steven_L_Intel1]

There are some attributes that require that the compiler know about the attribute when compiling the call. For example, OPTIONAL, or POINTER, or ALLOCATABLE or if the argument is deferred-shape. There are other attributes, such as INTEGER, that the compiler doesn't need to know.

I wrote about this many years ago in Doctor Fortran Gets Explicit. Since I wrote that, the set of cases where an explicit interface is required has grown (for example, if a dummy argument is a coarray).

That said, it is good Fortran programming practice to have an explicit interface visible for all procedures you call, so if you put all the routines in a module, that takes care of it and eliminates a large class of problems you may see when running the program.

By the way, I am not a "real doctor" - I just pretend to be one on the web.