Abstract Derived Type I/O

Ian_P_ · ‎01-14-2018

Is it not possible to write an abstract derived type I/O read and write procedure and then over-write it with an extension of the type? I'm running into error #8638: the type/rank signature for arguments of this specific subroutine is identical to another specific subroutine that shares the same defined I/O.

MODULE derived_io_test
    IMPLICIT NONE

    PRIVATE
    PUBLIC :: type1

    TYPE, ABSTRACT :: type1
        PRIVATE
        INTEGER, PUBLIC :: n_points = 1
    CONTAINS
        PROCEDURE(abs_read_form),  DEFERRED, PRIVATE :: read_form
        PROCEDURE(abs_write_form), DEFERRED, PRIVATE :: write_form
        GENERIC, PUBLIC :: READ  (FORMATTED) => read_form
        GENERIC, PUBLIC :: WRITE (FORMATTED) => write_form
    END TYPE type1

    CONTAINS

        SUBROUTINE abs_read_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type1),          INTENT(INOUT) :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        END SUBROUTINE abs_read_form

        SUBROUTINE abs_write_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type1),          INTENT(IN)    :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        END SUBROUTINE abs_write_form

    END MODULE derived_io_test

MODULE derived_io_extension
    USE derived_io_test, ONLY : type1

    TYPE, EXTENDS(type1) :: type2
        PRIVATE
    CONTAINS
        PROCEDURE, PRIVATE :: read_form   => type2_read_form
        PROCEDURE, PRIVATE :: write_form  => type2_write_form
        GENERIC, PUBLIC :: READ  (FORMATTED) => read_form
        GENERIC, PUBLIC :: WRITE (FORMATTED) => write_form
    END TYPE type2

    CONTAINS

        SUBROUTINE type2_read_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type2),          INTENT(INOUT) :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        END SUBROUTINE type2_read_form

        SUBROUTINE type2_write_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type2),          INTENT(IN)    :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        END SUBROUTINE type2_write_form
END MODULE derived_io_extension

FortranFan · ‎01-14-2018

@Ian P.,

A couple of problems with the code you show:

1) Note the accessibility of derived type components and procedure bindings is with respect to the MODULE, not the derived type. So you cannot provide a binding for DEFERRED procedure with PRIVATE attribute of an ABSTRACT type if the extended type is in another module, In your example code,

you will need to either make the deferred defined I/O bindings have the PUBLIC attribute, or
make the extended types part of the same module as the abstract one.

2) Once you have established a GENERIC binding with a procedure in a type - deferred or otherwise - you don't need to repeat it in the extension of that type. The GENERIC bindings on lines 53 and 54 are superfluous.

See a recent thread on a similar aspect where I have completely "lost my cool'" because of where things stand with support for OO based approaches in Fortran:

https://software.intel.com/en-us/forums/intel-visual-fortran-compiler-for-windows/topic/754000

Ian_P_ · ‎01-15-2018

@FortranFan, Thanks! The code now compiles but I'm running into an issue regardless of how I implement your changes outlined in #1 (making PUBLIC or put into same module). It will only call the abstract's READ/WRITE statements, not the extended type's read/write statements(I put in a simple print statement to check which one it was calling). I don't have this problem with user-defined operators (Such as:

GENERIC, PUBLIC :: OPERATOR(+) => add_two_vals

I only have this issue with read/write statements. Any further suggestions?

Updated code:

MODULE derived_io
    IMPLICIT NONE

    PRIVATE
    PUBLIC :: type1, type2

    TYPE, ABSTRACT :: type1
        PRIVATE
        INTEGER, PUBLIC :: n_points = 1
    CONTAINS
        PROCEDURE(abs_read_form),  DEFERRED, PRIVATE :: read_form
        PROCEDURE(abs_write_form), DEFERRED, PRIVATE :: write_form
        GENERIC, PUBLIC :: READ  (FORMATTED) => read_form
        GENERIC, PUBLIC :: WRITE (FORMATTED) => write_form
    END TYPE type1

    TYPE, EXTENDS(type1) :: type2
        PRIVATE
    CONTAINS
        PROCEDURE, PRIVATE :: read_form  => type2_read_form
        PROCEDURE, PRIVATE :: write_form => type2_write_form
!        GENERIC, PUBLIC :: READ  (FORMATTED) => read_form
!        GENERIC, PUBLIC :: WRITE (FORMATTED) => write_form
    END TYPE type2

    CONTAINS

        SUBROUTINE abs_read_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type1),          INTENT(INOUT) :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        END SUBROUTINE abs_read_form

        SUBROUTINE abs_write_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type1),          INTENT(IN)    :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        PRINT *, 'HI FROM ABS_WRITE_FORM'

        END SUBROUTINE abs_write_form

        SUBROUTINE type2_read_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type2),          INTENT(INOUT) :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        END SUBROUTINE type2_read_form

        SUBROUTINE type2_write_form (me, unit, iotype, v_list, iostat, iomsg)
        !>@brief
        !> Writes the dataset information from the .vtk file
        CLASS(type2),          INTENT(IN)    :: me
        INTEGER,               INTENT(IN)    :: unit
        INTEGER,               INTENT(OUT)   :: iostat
        CHARACTER(LEN=*),      INTENT(IN)    :: iotype
        CHARACTER(LEN=*),      INTENT(INOUT) :: iomsg
        INTEGER, DIMENSION(:), INTENT(IN)    :: v_list

        print *, 'HI FROM TYPE2_WRITE_FORM'

        END SUBROUTINE type2_write_form
END MODULE derived_io

PROGRAM scratch
    USE derived_io, ONLY : type1, type2
    IMPLICIT NONE

    CLASS(type1), ALLOCATABLE :: test_abs
    TYPE(type2) :: test_type_2

    ALLOCATE(type2::test_abs)

    OPEN(unit=8,file='test.txt',form='formatted')

    WRITE(unit=8,FMT='(DT)') test_abs
    WRITE(unit=8,FMT='(DT)') test_type_2

END PROGRAM scratch

FortranFan · ‎01-15-2018

Ian P. wrote:

.. I only have this issue with read/write statements. Any further suggestions? ..

@Ian P.,

You're now running into a bug in Intel Fortran, I suggest you submit a support incident at the Intel Online Service Center:

https://supporttickets.intel.com/?lang=en-US

FortranFan · ‎01-15-2018

By the way, there is another bug in Intel Fortran where your need to include defined I/O in an ABSTRACT type does NOT work, unfortunately.

Also, I assume you're using Intel Fortran 18.0 compiler (otherwise PUBLIC attribute on a GENERIC binding for defined I/O won't work either).

Under the circumstances, it appears the best you can do with Intel Fortran is defined I/O with a derived type that is not an extension type of an type with the ABSTRACT attribute.

Ian_P_ · ‎01-15-2018

@FortranFan,

Thanks for your help - I submitted (or at least hope I did) this as a bug with Intel Fortran 2018 Patch 1.

Note: I tested this with Intel 2018 Patch 1 for Windows & Linux and they both provide the error. I tested with gfortran 8.0.0 20171020(experimental) and it produces the correct result.