ISO_C_BINDING

Is this implemented fully?

For example C_F_POINTER doesn't seem to be recognised.

StamK

Fortran 2003 ISO_C_BINDING is implemented except for the intrinsics C_ASSOCIATED, C_F_POINTER and C_F_PROCPOINTER.

StamK

Do you have code that uses C_F_POINTER. Can you post a sample?

Sorry, somehow didn't get a notification of your reply. The code is the one in the accepted answer https://stackoverflow.com/questions/19147743/passing-allocatable-array-from-fortran-to-c-and-malloc-it Was trying to use malloc/free directly since we are having problems with get_storage@ etc.

StamK

If you are using only FTN95 then there will probably be a fix that we could provide. Alternatively we may be able to implement C_F_POINTER for you.

Either way we would need some sample code that illustrates what you want to do.

We just want to develop our own malloc/free Fortran calls, and iso_c_binding allows to use the C pointers seamlessly. In any case C_F_POINTER is a very important element of iso_c_binding so it is important to get it to work.

StamK

Can you post some code that illustrates how C_F_POINTER is used.

Courtesy of https://stackoverflow.com/questions/19147743/passing-allocatable-array-from-fortran-to-c-and-malloc-it

#include 'stdlib.h'
int *create_storage()
{
   /* Array of four integers. */
   return malloc(sizeof(int) * 4);
}

void destroy_storage(int *ptr)
{
   free(ptr);
}


PROGRAM fortran_side
  USE, INTRINSIC :: ISO_C_BINDING, ONLY: C_PTR, C_F_POINTER, C_INT
  IMPLICIT NONE
  INTERFACE
    FUNCTION create_storage() BIND(C, NAME='create_storage')
      USE, INTRINSIC :: ISO_C_BINDING, ONLY: C_PTR
      IMPLICIT NONE
      TYPE(C_PTR) :: create_storage
    END FUNCTION create_storage
    SUBROUTINE destroy_storage(p) BIND(C, NAME='destroy_storage')
      USE, INTRINSIC :: ISO_C_BINDING, ONLY: C_PTR
      IMPLICIT NONE
      TYPE(C_PTR), INTENT(IN), VALUE :: p
    END SUBROUTINE destroy_storage
  END INTERFACE
  TYPE(C_PTR) :: p
  INTEGER(C_INT), POINTER :: array(:)
  !****
  p = create_storage()
  CALL C_F_POINTER(p, array, [4])   ! 4 is the array size.
  ! Work with array...
  CALL destroy_storage(p)
END PROGRAM fortran_side

StamK

This code suggests to me that C_F_POINTER is equivalent to the FTN95 extension of using ABSOLUTE_ADDRESS with ALLOCATE...

ALLOCATE(array(4), ABSOLUTE_ADDRESS=p)

but I wonder why you would want to do this rather than simply call ALLOCATE(array(4)).

Also if GET_STORAGE@ does not work for you then we should look into that.

StamK

In the next release of the FTN95 library, the 64 bit definition of GET_STORAGE@ has been improved. You have reported that GET_STORAGE@ was not working for you and this change may make a difference.

This change will be in the next release of the DLLs.

Hi, is the implementation of C_ASSOCIATED going to happen any time soon? Thanks

StamK

I will put it on the wish list. I can't say when it will be implemented at the moment.

StamK

I have had a look at C_F_POINTER and my initial impression is that it will be a major task to add it to FTN95.

If you are having problems with GET_STORAGE@ then I am sure that it would be a lot quicker for us to fix that issue or for us to provide an alternative direct method for getting memory.

Please provide code that illustrates your problems when getting memory.

If you are writing a program for a Windows operating system then a call to get memory will almost certainly end up with a call to the Windows API function HeapAlloc.

This will be the case, for example, if you call ALLOCATE from Fortran, GET_STORAGE@ from FTN95 or malloc from a program written in the language C.

Here is a simple FTN95 program that illustrates how to directly call HeapAlloc.

PROGRAM main
STDCALL HeapAlloc 'HeapAlloc' (VAL7,VAL3,VAL7):INTEGER(7)
STDCALL GetProcessHeap 'GetProcessHeap':INTEGER(7)
STDCALL HeapFree 'HeapFree' (VAL7,VAL3,VAL7):INTEGER*4
INTEGER(7):: han,addr
INTEGER,PARAMETER:: HEAP_ZERO_MEMORY=8
INTEGER ret
han = GetProcessHeap()
addr = HeapAlloc(han, HEAP_ZERO_MEMORY, 1024_7)
IF(addr > 0) write(*, '(A,2Z8)') ' 1024 bytes of memory allocated:',han,addr
ret = HeapFree(han, 0, addr)
IF(ret /= 0) write(*,*) 'Memory has been de-allocated'
END PROGRAM