[Bug fortran/107441] New: optional arguments are identified as "present" when missing

[Bug fortran/107441] New: optional arguments are identified as "present" when missing

[kaiserkarl31 at yahoo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

            Bug ID: 107441
           Summary: optional arguments are identified as "present" when
                    missing
           Product: gcc
           Version: 12.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kaiserkarl31 at yahoo dot com
  Target Milestone: ---

If the first argument to a function is of type "character" (of any length, from
what I can tell, including ":" and "*") and the second parameter is both passed
by value and optional, the second argument will be identified as "present" even
when absent. The following short program reproduces the problem with gfortran
12.2.1:

program bugdemo

   implicit none
   character :: s
   integer :: t

   s = 'a'
   t = testoptional(s)
   print*, 'testoptional: ', t

contains

   function testoptional(w, x) result(t)

      character, intent(in) :: w
      integer, intent(in), value, optional :: x
      integer :: t

      print*, 'present(x) is ', present(x)
      t = 0

   end function testoptional

end program bugdemo
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

When compiled and run with gfortran 12.2.1, this gives the following output:
 present(x) is  T
 testoptional:            0
[clearly, the first line should have "F" instead of "T"]

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |anlauf at gcc dot gnu.org
           Keywords|                            |wrong-code
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-10-27

--- Comment #1 from anlauf at gcc dot gnu.org ---
Confirmed.

There is an inconsistency either in the generated code for the caller or
the callee:

integer(kind=4) testoptional (character(kind=1)[1:1] & restrict w,
integer(kind=4) x, integer(kind=8) _w, logical(kind=1) _x)

vs.

  t = testoptional (&s, 0, 0, 1);

How does the ABI define the ordering of character length and presence flag?

[Bug fortran/107441] optional arguments are identified as "present" when missing

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

kargl at gcc dot gnu.org changed:

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

--- Comment #2 from kargl at gcc dot gnu.org ---
(In reply to anlauf from comment #1)
> Confirmed.
> 
> There is an inconsistency either in the generated code for the caller or
> the callee:
> 
> integer(kind=4) testoptional (character(kind=1)[1:1] & restrict w,
> integer(kind=4) x, integer(kind=8) _w, logical(kind=1) _x)
> 
> vs.
> 
>   t = testoptional (&s, 0, 0, 1);
> 
> How does the ABI define the ordering of character length and presence flag?

Yep, there's an API issue.  If you use

   character(len=13) :: s

the produced code is

     t = testoptional (&s, 0, 0, 13);

so the hidden charlen is tacked on last whereas I think the hidden presence
argument is also expected to be last.  Likely a counting error in generating
the interface.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #3 from anlauf at gcc dot gnu.org ---
(In reply to kargl from comment #2)
> so the hidden charlen is tacked on last whereas I think the hidden presence
> argument is also expected to be last.  Likely a counting error in generating
> the interface.

I've found the code generating the function call in gfc_conv_procedure_call
(trans-expr.cc:7680)

  /* Add the return arguments.  */
  vec_safe_splice (retargs, arglist);

  /* Add the hidden present status for optional+value to the arguments.  */
  vec_safe_splice (retargs, optionalargs);

  /* Add the hidden string length parameters to the arguments.  */
  vec_safe_splice (retargs, stringargs);

  /* We may want to append extra arguments here.  This is used e.g. for
     calls to libgfortran_matmul_??, which need extra information.  */
  vec_safe_splice (retargs, append_args);


We now need the corresponding part on the procedure side.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #4 from anlauf at gcc dot gnu.org ---
(In reply to anlauf from comment #3)
> We now need the corresponding part on the procedure side.

That might be create_function_arglist (trans-decl.cc).
There's currently a single hidden_arglist, which needs
to be aligned to the caller's side.

Is there a public documentation what the ordering should be?

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #5 from anlauf at gcc dot gnu.org ---
(In reply to anlauf from comment #4)
> Is there a public documentation what the ordering should be?

It is actually documented for gfortran:

https://gcc.gnu.org/onlinedocs/gfortran/Argument-passing-conventions.html

The arguments are passed in the following order

* Result variable, when the function result is passed by reference
* Character length of the function result, if it is a of type CHARACTER and no
C binding is used
* The arguments in the order in which they appear in the Fortran declaration
* The present status for optional arguments with value attribute, which are
internally passed by value
* The character length and/or coarray token and offset for the first argument
which is a CHARACTER or a nonallocatable coarray dummy argument, followed by
the hidden arguments of the next dummy argument of such a type 

So it is create_function_arglist which is broken.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #6 from anlauf at gcc dot gnu.org ---
Created attachment 53782
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53782&action=edit
Patch

Regtesting the attached patch.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #7 from anlauf at gcc dot gnu.org ---
(In reply to anlauf from comment #6)
> Created attachment 53782 [details]
> Patch
> 
> Regtesting the attached patch.

Looks good for the reported issue.

However, while working on variations of the testcase, I hit an ICE for:

subroutine test3 (w)
  character, intent(in), value, optional :: w
  print*, 'present(w) is ', present(w)
end subroutine test3

It is not new, though.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #8 from anlauf at gcc dot gnu.org ---
(In reply to anlauf from comment #7)
> However, while working on variations of the testcase, I hit an ICE for:
> 
> subroutine test3 (w)
>   character, intent(in), value, optional :: w
>   print*, 'present(w) is ', present(w)
> end subroutine test3
> 
> It is not new, though.

This is now tracked in PR107444.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[sgk at troutmask dot apl.washington.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #9 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Thu, Oct 27, 2022 at 09:11:08PM +0000, anlauf at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441
> 
> --- Comment #8 from anlauf at gcc dot gnu.org ---
> (In reply to anlauf from comment #7)
> > However, while working on variations of the testcase, I hit an ICE for:
> > 
> > subroutine test3 (w)
> >   character, intent(in), value, optional :: w
> >   print*, 'present(w) is ', present(w)
> > end subroutine test3
> > 
> > It is not new, though.
> 
> This is now tracked in PR107444.
> 

If no other issues pop up and if this is an old issue,
you can probably commit your fix for current issue
as you've opened a new bug report.

Thanks for pecking away at gfortran bugs.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |anlauf at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #10 from anlauf at gcc dot gnu.org ---
Submitted: https://gcc.gnu.org/pipermail/fortran/2022-October/058398.html

[Bug fortran/107441] optional arguments are identified as "present" when missing

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Harald Anlauf <anlauf@gcc.gnu.org>:

https://gcc.gnu.org/g:e805adaa283129604a1fb305d0a1cf1e8a90c76e

commit r13-3863-ge805adaa283129604a1fb305d0a1cf1e8a90c76e
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Fri Oct 28 21:58:08 2022 +0200

    Fortran: ordering of hidden procedure arguments [PR107441]

    The gfortran ABI specifies the order of given and hidden procedure
arguments,
    where the hidden presence status flags of optional+value scalar arguments
    shall come before character length, coarray token and offset.  Respect
that.

    gcc/fortran/ChangeLog:

            PR fortran/107441
            * trans-decl.cc (create_function_arglist): Adjust the ordering of
            automatically generated hidden procedure arguments to match the
            documented ABI for gfortran.
            * trans-types.cc (gfc_get_function_type): Separate hidden
parameters
            so that the presence flag for optional+value arguments come before
            string length, coarray token and offset, as required.

    gcc/testsuite/ChangeLog:

            PR fortran/107441
            * gfortran.dg/coarray/pr107441-caf.f90: New test.
            * gfortran.dg/optional_absent_6.f90: New test.
            * gfortran.dg/optional_absent_7.f90: New test.

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |13.0

--- Comment #12 from anlauf at gcc dot gnu.org ---
Fixed on mainline for gcc-13.  Closing.

Thanks for the report!

[Bug fortran/107441] optional arguments are identified as "present" when missing

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107441

anlauf at gcc dot gnu.org changed:

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

--- Comment #13 from anlauf at gcc dot gnu.org ---
*** Bug 91196 has been marked as a duplicate of this bug. ***