[Bug libfortran/31532] New: INQUIRE(...,POSITION=...) not standard conforming

[Bug libfortran/31532] New: INQUIRE(...,POSITION=...) not standard conforming

[anlauf at gmx dot de]

Hi,

the attached code suggests that the implementation does not
conform to the F2003 standard w.r.t. the POSITION= specifier.

The standard says:

9.9.1.22 POSITION= specifier in the INQUIRE statement

 [...]
 If the file has been repositioned since the connection, the
 scalar-default-char-variable is assigned a processor-dependent value,
 which shall not be REWIND unless the file is positioned at its
 initial point and shall not be APPEND unless the file is positioned
 so that its endfile record is the next record or at its terminal
 point if it has no endfile record.


In my interpretation of the above wording, when positioned at the
endfile record, the result should be APPEND.

The attached program shows that the current libgfortran returns ASIS
in this case.  REWIND obviously works correctly.

The test program generates and then reads a file with a single line.
After reaching the end of file, it rewinds and reads again.
The output is:

 Generating test file containing one text line

 Open file
inquire: position = ASIS      nextrec = 1
 Reading...
Read line 1 : iostat = 0
inquire: position = ASIS      nextrec = 2
Read line 2 : iostat = -1
inquire: position = ASIS      nextrec = 2

 Rewind file
inquire: position = REWIND    nextrec = 1
 Reading...
Read line 1 : iostat = 0
inquire: position = ASIS      nextrec = 2
Read line 2 : iostat = -1
inquire: position = ASIS      nextrec = 2


In both cases, after attempting to read line 2, the
INQUIRE should return position = APPEND instead of ASIS.


-- 
           Summary: INQUIRE(...,POSITION=...) not standard conforming
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anlauf at gmx dot de
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[anlauf at gmx dot de]

------- Comment #1 from anlauf at gmx dot de  2007-04-10 21:35 -------
Created an attachment (id=13351)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13351&action=view)
Test program


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[fxcoudert at gcc dot gnu dot org]

------- Comment #2 from fxcoudert at gcc dot gnu dot org  2007-04-13 15:24 -------
(In reply to comment #0)
>  If the file has been repositioned since the connection, the
>  scalar-default-char-variable is assigned a processor-dependent value,
>  which shall not be REWIND unless the file is positioned at its
>  initial point and shall not be APPEND unless the file is positioned
>  so that its endfile record is the next record or at its terminal
>  point if it has no endfile record.

I'm not too skilled at reading normative language, but I guess it only says
that if we're not at endfile, if can't be APPEND. It doesn't say that when
we're at enfile, it shall be APPEND.

Of course, there also is the quality of implementation issue to consider.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[jvdelisle at gcc dot gnu dot org]

------- Comment #3 from jvdelisle at gcc dot gnu dot org  2007-04-14 00:40 -------
I have not a chance to study this yet, but I will get to it sometime soon.


-- 

jvdelisle at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jvdelisle at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-04-14 00:40:43
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[jvdelisle at gcc dot gnu dot org]

------- Comment #4 from jvdelisle at gcc dot gnu dot org  2007-04-14 03:10 -------
My interpretation of the standard as quoted in the original post.

The value of POSITION can only be APPEND if we are positioned just before the
EOF record or if there is no EOF record and the position is at it's terminating
point.  In the case given, there is an EOF record, so that rules that part out.

The question then is after the first read, what is the position?  The position
after the first read is just before the EOF record.  So the POSITION in this
case should be APPEND.

To fix this, we can have the INQUIRE statement attempt to read one more byte. 
If it is successful, we back up one byte and report ASIS.  If we get an EOF
trying to read the one more byte, the we report APPEND.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[patchapp at dberlin dot org]

------- Comment #5 from patchapp at dberlin dot org  2007-04-22 18:20 -------
Subject: Bug number PR31532

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01415.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[jvdelisle at gcc dot gnu dot org]

------- Comment #6 from jvdelisle at gcc dot gnu dot org  2007-04-28 03:03 -------
Subject: Bug 31532

Author: jvdelisle
Date: Sat Apr 28 03:03:21 2007
New Revision: 124252

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=124252
Log:
2007-04-27  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

        PR libfortran/31532
        * io/file_pos.c (st_backspace): Set flags.position for end of file
        condition and use new function update_position.
        (st_endfile): Use new function update_position.
        * io/io.h: Add prototype for new function.
        * io/inquire.c (inquire_via_unit): If not direct access, set NEXTREC
        to zero.
        * io/unit.c (update_position): New function to update position info
        used by inquire.
        * io/transfer.c (next_record): Fix typo and use new function.

Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/io/file_pos.c
    trunk/libgfortran/io/inquire.c
    trunk/libgfortran/io/io.h
    trunk/libgfortran/io/transfer.c
    trunk/libgfortran/io/unit.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[jvdelisle at gcc dot gnu dot org]

------- Comment #7 from jvdelisle at gcc dot gnu dot org  2007-04-28 03:04 -------
Subject: Bug 31532

Author: jvdelisle
Date: Sat Apr 28 03:04:35 2007
New Revision: 124254

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=124254
Log:
2007-04-27  Jerry DeLisle

        PR libfortran/31532
        * gfortran.dg/inquire_5.f90: Update test.

Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/inquire_5.f90


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532

[Bug libfortran/31532] INQUIRE(...,POSITION=...) not standard conforming

[jvdelisle at gcc dot gnu dot org]

------- Comment #8 from jvdelisle at gcc dot gnu dot org  2007-04-28 03:13 -------
Fixed on trunk.


-- 

jvdelisle at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31532