[Bug fortran/44477] New: Sequential I/O with END FILE: File position should be at EoF

[Bug fortran/44477] New: Sequential I/O with END FILE: File position should be at EoF

[burnus at gcc dot gnu dot org]

Based on
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/cfb5f9dca46d5114#

After ENDFILE for non-streams, the current file position should be at the
endfile record. Thus, running the program below with NAG gives:
  READ/WRITE attempted after ENDFILE on unit 10
  Program terminated by I/O error on unit 10 (File="XXX",Formatted,Sequential)

And with Pathf95:
  A WRITE operation is invalid if the file is positioned after the end-of-file.

While with gfortran it simply runs. (Ditto for g95 and ifort.) [One could
continue to do so as extension, but one should do so knowingly.]


F2008: "9.8.3 ENDFILE statement"

"Execution of an ENDFILE statement for a file connected for sequential access
writes an endfile record as the next record of the file. The file is then
positioned after the end file record, which becomes the last record of the 
file. If the file also may be connected for direct access, only those records
before the endfile record are considered to have been written. Thus, only those
records may be read during subsequent direct access connections to the \ffile.
   After execution of an ENDFILE statement for a file connected for sequential
access, a BACKSPACE or REWIND statement shall be used to reposition the \ffile
prior to execution of any data transfer input/output statement or ENDFILE
statement.
   Execution of an ENDFILE statement for a \ffile connected for stream access
causes the terminal point of the \ffile to become equal to the current file
position. Only file storage units before the current position are considered to
have been written; thus only those \ffile storage units may be subsequently
read. Subsequent stream output statements may be used to write further data to
the file.
   Execution of an ENDFILE statement for a file that is connected but does not
exist creates the file; if the \ffile is connected for sequential access, it is
created prior to writing the endfile record."


!-------------------------------------------
       OPEN(10, FILE='XXX', FORM='FORMATTED', &
                 ACTION='WRITE', POSITION='REWIND')
        ENDFILE(10)
      write(10,*) 'aa'
end


-- 
           Summary: Sequential I/O with END FILE: File position should be at
                    EoF
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #1 from jvdelisle at gcc dot gnu dot org  2010-06-09 19:24 -------
As I read this, the test case is invalid since it does not have a rewind or
backspace before the write?

If we want to change this to be an intended extension, I suppose we should
issue a warning or error for -std= ?

I want to study this more before we do anything.  Regression territory here.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[burnus at gcc dot gnu dot org]

------- Comment #2 from burnus at gcc dot gnu dot org  2010-06-09 19:41 -------
(In reply to comment #1)
> As I read this, the test case is invalid since it does not have a rewind or
> backspace before the write?

Yes - I expect that gfortran should issue an EOR error instead of happily
accepting an I/O transfer.


> If we want to change this to be an intended extension, I suppose we should
> issue a warning or error for -std= ?

Well, I think we can do two things:

a) Keep the current status and claim it is an extension
b) Change it to match NAG f95 and Pathscale and print a run-time EoF error. (Or
the equivalent for ERR=/IOSTAT=/IOMSG=.)

I do not think that it makes sense to allow it for -std=(gnu/legacy) and not
for -std=f(95/2003/2008).

As Pathscale prints an error, there is hope that not too many programs rely on
having no BACKSPACE/REWIND.


Error: Pathscale 3.2.99, NAG f95 v5.1, Open64 4.2

No error: ifort 11.1, gfortran, g95, sunf95 8.3 (sunstudio12), Portland's pgf90
v6.2 and v10.3.
(No idea what g77 did.)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[burnus at gcc dot gnu dot org]

------- Comment #3 from burnus at gcc dot gnu dot org  2010-06-11 16:27 -------
For completeness, also Cray Fortran 7.2.3 prints:
  A WRITE operation is invalid if the file is positioned after the end-of-file.

Updated summary:
- Error with: NAG f95 v5.1, Pathscale pathf95 3.2.99, Cray ftn 8.2.3, Open64
4.2
- No error with: ifort 11.1, gfortran, g95, sunf95 8.3 (sunstudio12),
Portland's pgf90
v6.2 and v10.3.
- Unknown: g77, ...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #4 from jvdelisle at gcc dot gnu dot org  2010-06-12 22:33 -------
How about this when attempting a READ or WRITE after an ENDFILE. (original
testcase)

$ gfc pr44477.f90 
$ ./a.out 
At line 5 of file pr44477.f90 (unit = 10, file = 'XXX')
Fortran runtime error: Sequential READ or WRITE not allowed after EOF marker,
possibly use REWIND or BACKSPACE

and then this for an ENDFILE after an ENDFILE.

$ ./a.out 
At line 5 of file pr44477.f90 (unit = 10, file = 'XXX')
Fortran runtime error: Cannot perform ENDFILE on a file already positiond after
the EOF marker

Patch testing.


-- 

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         |2010-06-12 22:33:42
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #5 from jvdelisle at gcc dot gnu dot org  2010-06-19 00:58 -------
Subject: Bug 44477

Author: jvdelisle
Date: Sat Jun 19 00:58:28 2010
New Revision: 161020

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=161020
Log:
2010-06-18  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

        PR libfortran/44477
        * io/file_pos.c (st_endfile): Add check for ENDFILE when file is
        already positioned after the EOF marker. Use find_or_create_unit
        instead of find_unit. If unit is not connected, connect it and create 
        the file with default settings.
        * io/transfer.c (data_transfer_init):  Add check for attempted READ or
        WRITE when file is already positioned after the EOF marker.

Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/io/file_pos.c
    trunk/libgfortran/io/transfer.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #6 from jvdelisle at gcc dot gnu dot org  2010-06-19 01:05 -------
Subject: Bug 44477

Author: jvdelisle
Date: Sat Jun 19 01:05:05 2010
New Revision: 161021

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=161021
Log:
2010-06-18  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

        PR libfortran/44477
        * gfortran.dg/eof_3.f90
        * gfortran.dg/endfile_2.f90
        * gfortran.dg/endfile_4.f90
        * gfortran.dg/endfile_3.f90

Added:
    trunk/gcc/testsuite/gfortran.dg/endfile_3.f90
    trunk/gcc/testsuite/gfortran.dg/endfile_4.f90
Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/endfile_2.f90
    trunk/gcc/testsuite/gfortran.dg/eof_3.f90


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[michael dot a dot richmond at nasa dot gov]

------- Comment #7 from michael dot a dot richmond at nasa dot gov  2010-06-20 16:14 -------
The following occurs in the snapshot of June 19, but not in earlier snapshots:

mrichmon@msc545ux:~$ cat test.f90
PROGRAM test
END FILE 10
END FILE 10
END PROGRAM test
mrichmon@msc545ux:~$ gfortran test.f90
mrichmon@msc545ux:~$ ./a.out
At line 3 of file test.f90 (unit = 10, file = 'fort.10')
Fortran runtime error: Cannot perform ENDFILE on a file already positioned
after the EOF marker


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[kargl at gcc dot gnu dot org]

------- Comment #8 from kargl at gcc dot gnu dot org  2010-06-20 16:41 -------
(In reply to comment #7)
> The following occurs in the snapshot of June 19, but not in earlier snapshots:
> 
> mrichmon@msc545ux:~$ cat test.f90
> PROGRAM test
> END FILE 10
> END FILE 10
> END PROGRAM test
> mrichmon@msc545ux:~$ gfortran test.f90
> mrichmon@msc545ux:~$ ./a.out
> At line 3 of file test.f90 (unit = 10, file = 'fort.10')
> Fortran runtime error: Cannot perform ENDFILE on a file already positioned
> after the EOF marker
> 

Did you read the error message?  The code is invalid.  For the Fortran 95
standard:

   After execution of an ENDFILE statement, a BACKSPACE or REWIND
   statement shall be used to reposition the file prior to execution
   of any data transfer input/output statement or ENDFILE statement.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #9 from jvdelisle at gcc dot gnu dot org  2010-06-20 19:57 -------
Michael, is this a legacy code issue? two ENDFILE in a row?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[michael dot a dot richmond at nasa dot gov]

------- Comment #10 from michael dot a dot richmond at nasa dot gov  2010-06-22 11:55 -------
(In reply to comment #9)
> Michael, is this a legacy code issue? two ENDFILE in a row?
> 

It is legacy code


-- 

michael dot a dot richmond at nasa dot gov changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |michael dot a dot richmond
                   |                            |at nasa dot gov


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[burnus at gcc dot gnu dot org]

------- Comment #11 from burnus at gcc dot gnu dot org  2010-06-22 13:01 -------
(In reply to comment #10)
> (In reply to comment #9)
> > Michael, is this a legacy code issue? two ENDFILE in a row?
> It is legacy code

Any idea how to best deal with this?

The standard is pretty clear that it is invalid (cf. comment 0 and comment 8) -
though the standard is pretty weak about what a conforming "processor" (i.e.
compiler + run-time library) shall do for I/O, thus, there is some freedom.

For the example in comment 0, several compilers print a run-time error:
  NAG f95 v5.1, Pathscale pathf95 3.2.99, Cray ftn 8.2.3, Open64 4.2, gfortran
4.6

If there has been no file access (write/read/open/rewind) before the first,
ENDFILE, the second ENDFILE succeeds with crayftn, openf95, and pathf95. (NAG
has the bogus error that the file is not open.) While (cf. comment 6) with
gfortran there is an error for the second endfile.

For the legacy program, would it be enough to allow - similarly to
Cray/Open64/Pathscale - two ENDFILEs on unopened files? Or do you also use
other endfile/endfile combinations? (If so, the program should also fail
Cray/Open64/Pathscale/NAG.)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[michael dot a dot richmond at nasa dot gov]

------- Comment #12 from michael dot a dot richmond at nasa dot gov  2010-06-22 13:02 -------
I will modify my code


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #13 from jvdelisle at gcc dot gnu dot org  2010-06-23 02:37 -------
Closing as fixed.  If the issue of double endfile sequences pops up again we
can consider putting th errors behind -std=legacy.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477

[Bug fortran/44477] Sequential I/O with END FILE: File position should be at EoF

[jvdelisle at gcc dot gnu dot org]

------- Comment #14 from jvdelisle at gcc dot gnu dot org  2010-06-23 02:37 -------
Closed


-- 

jvdelisle at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44477