[Bug libfortran/24700] New: Bad write after backing up from end of file

[Bug libfortran/24700] New: Bad write after backing up from end of file

[jvdelisle at gcc dot gnu dot org]

The following program from http://gcc.gnu.org/ml/fortran/2005-11/msg00084.html
incorrectly writesthe 'TEST' file.  Thanks to Georgy Salnikov for finding and
submitting this bug.  

      PROGRAM TEST
      CHARACTER*8 TXT
      DATA TXT/'**TEST**'/
      OPEN (1, FILE='TEST', STATUS='UNKNOWN', FORM='UNFORMATTED')
      WRITE (1) TXT
      REWIND 1
      READ (1, END=1) TXT
      READ (1, END=1) TXT
 1    CONTINUE
      BACKSPACE 1
      WRITE (1) TXT
      CLOSE (1, STATUS='KEEP')
      END

Georgy also submitted a patch which is considered obvious:

diff -Naur gcc-4.0.2.orig/libgfortran/io/transfer.c
gcc-4.0.2/libgfortran/io/transfer.c
--- gcc-4.0.2.orig/libgfortran/io/transfer.c    2005-09-12 01:55:16.000000000
+0700
+++ gcc-4.0.2/libgfortran/io/transfer.c 2005-10-15 12:29:13.000000000 +0700
@@ -1641,11 +1641,13 @@
          {
            generate_error (ERROR_END, NULL);
            current_unit->endfile = AFTER_ENDFILE;
+           current_unit->current_record = 0;
          }
        break;

       case AFTER_ENDFILE:
        generate_error (ERROR_ENDFILE, NULL);
+       current_unit->current_record = 0;
        break;
       }
 }

Test results to follow:


-- 
           Summary: Bad write after backing up from end of file
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: jvdelisle at gcc dot gnu dot org
        ReportedBy: jvdelisle at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24700

[Bug libfortran/24700] Bad write after backing up from end of file

[jvdelisle at gcc dot gnu dot org]

------- Comment #1 from jvdelisle at gcc dot gnu dot org  2005-11-06 23:58 -------
Testing that patch gives the following results.  I will put together a test
case and commit this as obvious unless there are objections.

hex dump of TEST file created using gfortran 4.0.1 gives, with no patch:

$ xxd TEST
0000000: 0800 0000 0000 0000 2a2a 5445 5354 2a2a  ........**TEST**
0000010: 0800 0000 0000 0000 0800 0000 0000 0000  ................
0000020: 2a2a 5445 5354 2a2a 0800 0000 0000 0000  **TEST**........

With gfortran 4.1 we get:

$ xxd TEST
0000000: 0800 0000 0000 0000 2a2a 5445 5354 2a2a  ........**TEST**
0000010: 0800 0000 0000 0000 2a2a 5445 5354 2a2a  ........**TEST**
0000020: ffff ffff ffff ff7f                      ........

With Georgy's patch on 4.0.3:

$ xxd TEST
0000000: 0800 0000 0000 0000 2a2a 5445 5354 2a2a  ........**TEST**
0000010: 0800 0000 0000 0000 0800 0000 0000 0000  ................
0000020: 2a2a 5445 5354 2a2a 0800 0000 0000 0000  **TEST**........

With Georgy's patch on 4.1:

$ xxd TEST
0000000: 0800 0000 0000 0000 2a2a 5445 5354 2a2a  ........**TEST**
0000010: 0800 0000 0000 0000 0800 0000 0000 0000  ................
0000020: 2a2a 5445 5354 2a2a 0800 0000 0000 0000  **TEST**........

So it appears we had a regression from 4.0.1 in there somehow and did not catch
it. 

Regards

Jerry


-- 

jvdelisle at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-11-06 23:58:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24700

[Bug libfortran/24700] Bad write after backing up from end of file

[jvdelisle at gcc dot gnu dot org]

------- Comment #2 from jvdelisle at gcc dot gnu dot org  2005-11-11 18:52 -------
*** Bug 24796 has been marked as a duplicate of this bug. ***


-- 

jvdelisle at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |chjacob at web dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24700

[Bug libfortran/24700] Bad write after backing up from end of file

[jvdelisle at gcc dot gnu dot org]

------- Comment #3 from jvdelisle at gcc dot gnu dot org  2005-11-12 23:13 -------
Fixed in 4.0.3 and 4.1.


-- 

jvdelisle at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24700

[Bug libfortran/24700] Bad write after backing up from end of file

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24700