[Bug fortran/104100] New: Passing an allocated array to a C bind function alters the bounds

[Bug fortran/104100] New: Passing an allocated array to a C bind function alters the bounds

[hzhou321 at anl dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100

            Bug ID: 104100
           Summary: Passing an allocated array to a C bind function alters
                    the bounds
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hzhou321 at anl dot gov
  Target Milestone: ---

https://github.com/pmodels/mpich/issues/4170#issuecomment-1015580478

Minimum reproducer:
`t.f90`:
```
program t
    INTERFACE
        SUBROUTINE F_cdesc(buf) bind(C, name="F_cdesc")
            IMPLICIT NONE
            TYPE(*), DIMENSION(..), INTENT(in) :: buf
        END SUBROUTINE
    END INTERFACE

    ! Only reproducible with allocatable array. "INTEGER:: A(5)" would be fine.
    INTEGER, allocatable, dimension(:):: A

    allocate(A(5))

    A = (/1, 2, 3, 4, 5/);
    print*, A
    write(*,'(a6,2(1x,i2))') 'Before:', lbound(A), ubound(A)

    ! "CALL F_cdesc(A)" would be fine
    CALL f08ts(A)

    print*, A
    write(*,'(a6,2(1x,i2))') 'After:', lbound(A), ubound(A)

    deallocate(A)

    contains
    SUBROUTINE f08ts(buf)
        IMPLICIT NONE
        TYPE(*), DIMENSION(..), INTENT(in) :: buf
        call F_cdesc(buf)
    END SUBROUTINE f08ts
end
```
`cdesc.c`:
```
#include <ISO_Fortran_binding.h>

void F_cdesc(CFI_cdesc_t *buf) { }
```
Run with:
```
gcc-9 -c -o cdesc.o cdesc.c && gfortran-9 t.f90 cdesc.o -o t && ./t
```

Results:
```
           1           2           3           4           5
Before  1  5
           1           2           3           4           5
After:  0  4
```

EDIT: also reproduced with `gcc 11`

[Bug fortran/104100] Passing an allocated array to a C bind function alters the bounds

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kargl at gcc dot gnu.org
      Known to work|                            |12.0

--- Comment #1 from kargl at gcc dot gnu.org ---
Works with 12.0

% ~/work/bin/gcc -c -O aa.c
% gfcx -o z a.f90 -O aa.o
% ./z
           1           2           3           4           5
Before  1  5
           1           2           3           4           5
After:  1  5

Thanks for the bug report, but it should likely be closed with
WONTFIX due to the complexity of the changes to ISO_Fortran_binding.h
and CFI support.  I'll let active gfortran contributors make that 
decision.

[Bug fortran/104100] Passing an allocated array to a C bind function alters the bounds

[hzhou321 at anl dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100

--- Comment #2 from Hui Zhou <hzhou321 at anl dot gov> ---
Great! That means it has already been fixed in the coming 12 series, right? I
was initially a bit confused with your WONTFIX comment.

[Bug fortran/104100] Passing an allocated array to a C bind function alters the bounds

[sgk at troutmask dot apl.washington.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100

--- Comment #3 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Tue, Jan 18, 2022 at 10:15:25PM +0000, hzhou321 at anl dot gov wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100
> 
> --- Comment #2 from Hui Zhou <hzhou321 at anl dot gov> ---
> Great! That means it has already been fixed in the coming 12 series, right? I
> was initially a bit confused with your WONTFIX comment.
> 

Yes, it is fixed in the mainline of development, which is 
expected to be branched for 12.1 in a few days/week.  The
changes are fairly extensive.  I don't know if there are
plans to backport to 11-branch.

[Bug fortran/104100] Passing an allocated array to a C bind function alters the bounds

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-01-19
                 CC|                            |sandra at codesourcery dot com
     Ever confirmed|0                           |1

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
eventually some pieces might qualify for backporting, lets ask Sandra.

[Bug fortran/104100] Passing an allocated array to a C bind function alters the bounds

[sandra at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104100

sandra at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sandra at gcc dot gnu.org

--- Comment #5 from sandra at gcc dot gnu.org ---
Most of the patches are on the devel/omp/gcc-11 development branch that also
includes a bunch of other experimental features and preliminary patches that
haven't made it to mainline yet, but I don't think either Tobias or I have a
todo item to backport the bind(c) patches to the stable gcc 11 branch.  There
were a lot of patches and some of them were quite extensive rewrites, so my
sense is that it's probably not appropriate for a stable branch.