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From: "kargl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/110825] New: TYPE(*) dummy argument to generate an
 unused hidden argument
Date: Wed, 26 Jul 2023 20:17:07 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: fortran
X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110825

            Bug ID: 110825
           Summary: TYPE(*) dummy argument to generate an unused hidden
                    argument
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kargl at gcc dot gnu.org
  Target Milestone: ---

The was pointed out in Fortran Discourse,

https://fortran-lang.discourse.group/t/strange-behaviour-when-using-type-an=
d-character-in-gfortran/6233

that gfortran generates wrong code for a valid program.  Here's a slightly
modified version of the program.

  program foo

    implicit none

    character(100) :: not_used
    call sub(not_used, "123")

    contains

    subroutine sub(useless_var, print_this)
        type(*), intent(in)      :: useless_var
        character(*), intent(in) :: print_this
        if (len_trim(print_this) /=3D 3) stop 1
    end subroutine sub

  end

The subroutine reference in the main program is generating a call with two
hidden arguments.  From -fdump-tree-original,=20

void MAIN__ ()
{
  static void sub (void * & restrict, character(kind=3D1)[1:] & restrict,
integer(kind=3D8));
  character(kind=3D1) not_used[1:100];

  sub (&not_used, &"123"[1]{lb: 1 sz: 1}, 100, 3);
}

we have hidden arguments 100 and 3.  However, the code generated for the
contained subroutine is only expecting one hidden argument.

__attribute__((fn spec (". r r ")))
void sub (void * & restrict useless_var,
   character(kind=3D1)[1:_print_this] & restrict print_this,
   integer(kind=3D8) _print_this)
{
...
}

Thus, when compiled and executed the program hits 'STOP 1'.  Likely, gfortr=
an
needs to add a possibly unused hidden argument to the argument list for a
TYPE(*) dummy argument.=