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Workaround for C_F_POINTER
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jlb



Joined: 21 Oct 2020
Posts: 80
PostPosted: Tue Nov 05, 2024 3:23 pm    Post subject: Reply with quote
Paul
Thank you for the clarification.
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PaulLaidler
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Joined: 21 Feb 2005
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PostPosted: Tue Nov 05, 2024 5:18 pm    Post subject: Reply with quote
jlb

I should have added...

Users with a support licence are notified directly about full releases by Silverfrost Ltd.

Users of the personal edition can download full releases from the Silverfrost.com website.
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jlb



Joined: 21 Oct 2020
Posts: 80
PostPosted: Tue Nov 05, 2024 5:28 pm    Post subject: Reply with quote
Paul
Thank you. I was just wondering as the new implementation was announced for an interim release, but the also needed mod file as in a full release.
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jlb



Joined: 21 Oct 2020
Posts: 80
PostPosted: Wed Feb 26, 2025 1:41 pm    Post subject: Reply with quote
Using FTN95 v. 9.10, a call like
Code:
CALL C_F_POINTER(c_string_pointer, char_array_pointer, [255])

still produces an error at compile time
Quote:
error 1251 - Invalid arguments in call to C_F_POINTER

Note: Looking inside ISO_C_BINDING.MOD (in \Silverfrost\FTN95\include) with a editor doesn't show any string C_F_POINTER
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PaulLaidler
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PostPosted: Wed Feb 26, 2025 4:52 pm    Post subject: Reply with quote
jlb

C_F_POINTER does not appear in the module because it has to be created by FTN95.

It is non-trivial and I found it difficult to use. The sample program below works for x64 and uses a test function defined in ClearWin64.dll.

Code:
program main
  use iso_c_binding,only:c_ptr,c_f_pointer
  implicit none
  interface
    subroutine c_f_pointer_test$(p) bind(c,name='__c_f_pointer_test')
      import :: c_ptr
      type(c_ptr), intent(out) :: p
    end subroutine
  end interface
  type(c_ptr) :: cptr
  real,pointer :: a(:)
  real,pointer :: b(:,:)
  real,pointer :: c
  real::ss1,ss2
  integer s(1)
  call c_f_pointer_test$(cptr)
  s = [12]
  call c_f_pointer(cptr, a, s)
  ss1 = sum(a)
  call c_f_pointer(cptr, b, [3,4])
  ss2 = sum(b)
  call c_f_pointer(cptr, c)
  if(ss1 == ss2 .and. c == 1.0) print*, "Success"
end program main


Code:
extern "C" void __c_f_pointer_test(float*& a)
{
  a = (float*)malloc(12 * sizeof(float));
  float* b = a;
  for (int i = 1; i <= 12; ++i) *b++ = (float)i;
}
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jlb



Joined: 21 Oct 2020
Posts: 80
PostPosted: Thu Feb 27, 2025 12:35 pm    Post subject: Reply with quote
Paul
Thanks for providing me with a working example. It allowed me to create a reproducer for error 1251 at compile time using FTN95 v.9.10 x64. The reproducer compiles with ifort.
Code:
program main
  use iso_c_binding,only:c_ptr,c_f_pointer
  implicit none
  interface
    subroutine c_f_pointer_test$(q) bind(c,name='__c_f_pointer_test')
      import :: c_ptr
      type(c_ptr), intent(out) :: q
    end subroutine
  end interface
  type(c_ptr) :: cptr
  REAL :: X
 
  call c_f_pointer_test$(cptr)
  X=TEST(cptr)
  PRINT*, X
 
  CONTAINS
 
  REAL FUNCTION TEST(J)
  implicit none
  type(c_ptr), INTENT(IN) :: J
  real,pointer :: a(:)
  real,pointer :: b(:,:)
  real,pointer :: c
  real::ss1,ss2
  integer s(1)
  s = [12]
  call c_f_pointer(J, a, s)
  ss1 = sum(a)
  call c_f_pointer(J, b, [3,4])
  ss2 = sum(b)
  call c_f_pointer(J, c)
  if(ss1 == ss2 .and. c == 1.0) print*, "Success"
  TEST=a(12)
  END FUNCTION TEST
 
end program main
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PaulLaidler
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PostPosted: Thu Feb 27, 2025 12:45 pm    Post subject: Reply with quote
jlb

Thank you for the bug report. I have logged this for investigation.
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PaulLaidler
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PostPosted: Tue Mar 11, 2025 2:38 pm    Post subject: Reply with quote
This failure has now been fixed for the next release of FTN95.
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jlb



Joined: 21 Oct 2020
Posts: 80
PostPosted: Wed Mar 12, 2025 10:48 am    Post subject: Reply with quote
Paul

Thank you for your prompt assistance. Is this an interim release or a full release of FTN95?
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PaulLaidler
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PostPosted: Wed Mar 12, 2025 1:02 pm    Post subject: Reply with quote
It will probably be an interim release following the full release of the personal edition of FTN95 v9.10.
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jlb



Joined: 21 Oct 2020
Posts: 80
PostPosted: Fri May 30, 2025 10:27 am    Post subject: Reply with quote
Paul

Compiling your working example with FTN95 version 9.11 fails now with the following error
Quote:
error 463 - Invalid characters(s) after SUBROUTINE expression

pointing at
Code:
subroutine c_f_pointer_test$(p) bind(c,name='__c_f_pointer_test')
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PaulLaidler
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Location: Salford, UK
PostPosted: Sat May 31, 2025 7:31 am    Post subject: Reply with quote
jlb

There is a regression at v9.11 regarding BIND(C...). I will aim to upload a fix shortly.
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AlejandroP



Joined: 11 Apr 2025
Posts: 1
PostPosted: Thu Oct 30, 2025 8:49 pm    Post subject: Reply with quote
Hi all,
I am reaching out to ask if there are any updates regarding support for C_F_POINTER and C_LOC in subroutines.
Currently, I am unable to use these features within subroutines, although they seem to work fine in a program context, as shown below:

Code:
       program main
       use,intrinsic::iso_c_binding

      implicit none
     
      interface
      subroutine c_f_pointer_test(p)
     & bind(c,name='__c_f_pointer_test')
      import :: c_ptr
      type(c_ptr), intent(out) :: p
      end subroutine
      end interface
     
      type(c_ptr) :: cptr
      real,pointer :: a(:)
      real,pointer :: b(:,:)
      real,pointer :: c


      logical L(6)
     
      L(1) = .not.c_associated(cptr)

      call c_f_pointer_test(cptr)      ! Create cptr
      shp = 12
     
      call c_f_pointer(cptr, a, [12])  ! 'a' points to cptr.
      call c_f_pointer(cptr, b, [3,4]) ! 'b' has the same target as 'a' but different shape.
      call c_f_pointer(cptr, c)        ! 'c' is just the first element of the cptr array.
      L(3) = c_associated(cptr)
      L(4) = c_associated(cptr, c_loc(a))
      L(5) = c_associated(cptr, c_loc(b))
      L(6) = c_associated(cptr, c_loc(c))

      if(all(L)) print*, "Success"
      end program main



I am currently working with version 9.10. Is there a planned release that will extend support for these features in subroutines?
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