From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 23EA53857812; Mon, 14 Sep 2020 14:45:04 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 23EA53857812
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1600094704;
 bh=khyIVZBRPwM3j+DFLDsbNpd/u8GFWxinxk0gi/6krA4=;
 h=From:To:Subject:Date:From;
 b=CLZ0wyUUgG4cV1eUkqiNtctYTY0xLALW9y/Zt/whTQ1Ou/bRZLCSnvPzwoYqmeEdA
 0G/03c0XKc6eBNyNteq+CO9nm+F8I15JkVTdC64ImliE/yOKH8OyCXfDnBkD04xtHC
 X1kfAT9ka9MhhrJTjowkqsheFhQO8SbFi2Uaoqr4=
From: "igor.gayday at mu dot edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/97045] New: A wrong column is selected when addressing
 individual elements of unlimited polymorphic dummy argument
Date: Mon, 14 Sep 2020 14:45:03 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: fortran
X-Bugzilla-Version: 10.2.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: igor.gayday at mu dot edu
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-97045-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Mon, 14 Sep 2020 14:45:04 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97045

            Bug ID: 97045
           Summary: A wrong column is selected when addressing individual
                    elements of unlimited polymorphic dummy argument
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: igor.gayday at mu dot edu
  Target Milestone: ---

Consider the following Fortran program:

program test_prg
  implicit none
  integer :: i
  integer, allocatable :: arr(:, :)

  arr =3D reshape([(i, i =3D 1, 100)], [10, 10])
  do i =3D 1, 3
    print *, 'Column', i
    call write_array(arr(1:2, i))=20
  end do

contains

  subroutine write_array(array)
    class(*), intent(in) :: array(:)
    integer :: i

    do i =3D 1, size(array)
      select type (elem =3D> array(i))
        type is (integer)
          print '(I0)', elem
      end select
    end do
  end subroutine


  subroutine write_array_alt(array)
    class(*), intent(in) :: array(:)
    integer :: i

    select type (array)
      type is (integer)
        print '(I0)', array
    end select
  end subroutine

end program

Compiled with gfortran 9.3.0 (and 10.2), the program prints:

 Column           1
1
2
 Column           2
21
22
 Column           3
41
42

As you can see, it skips every other column. If I replace the call to
write_array with the call to write_array_alt, where I select type of the wh=
ole
array and not individual elements, then every column is printed, as expecte=
d.

This issue was originally reported here:
https://stackoverflow.com/questions/63841012/a-wrong-column-is-selected-whe=
n-addressing-individual-elements-of-unlimited-poly=