[Bug fortran/19451] New: Some read and write confusion with a read-only file

[Bug fortran/19451] New: Some read and write confusion with a read-only file

[Thomas dot Koenig at online dot de]

$ cat open+write.f90
program main
  character(len=10) a
  call system("rm -f asdf.dat; touch asdf.dat; chmod u-w asdf.dat")
  open(file="asdf.dat",unit=10,err=999,action="read")
  write(10,*,err=20) "Hello, world"
  print *,"write to read-only file succeeded"
  call abort
20 continue
  ! rewind(10)
  read(10,'(A)',end=30,err=999) a
  print *,"read from empty file succeeded"
  call abort
999 continue
  print *,"error reading from read-only file"
  call abort
30 continue
  print *,"Success!"
end
$ gfortran open+write.f90
$ ./a.out
 error reading from read-only file
Aborted

Uncommenting the rewind statement leads to

$ ./a.out
 read from empty file succeeded
Aborted
$ gfortran -v ; gfortran -dumpmachine
Using built-in specs.
Configured with: ../gcc-4.0-20050109/configure --prefix=/home/zfkts
--enable-languages=c,c++,f95
Thread model: posix
gcc version 4.0.0 20050109 (experimental)
ia64-unknown-linux-gnu

-- 
           Summary: Some read and write confusion with a read-only file
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Thomas dot Koenig at online dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Some read and write confusion with a read-only file

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|fortran                     |libfortran


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Read after a write with a read only file

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-15 08:08 -------
Confirmed, changing the summary a little more.

Also if the file contained anything, we seg fault when finishing the write (which seems wrong).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-01-15 08:08:37
               date|                            |
            Summary|Some read and write         |Read after a write with a
                   |confusion with a read-only  |read only file
                   |file                        |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Read after a write with a read only file

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-01-19 21:35 -------
(In reply to comment #1)
> Confirmed, changing the summary a little more.
> 
> Also if the file contained anything, we seg fault when finishing the write
(which seems wrong).

Here's a test case for that:

$ cat open+write2.f90
program main
  call system("rm -f asdf.dat; echo foo > asdf.dat; chmod u-w asdf.dat")
  open(file="asdf.dat",unit=10,action="read")
  write(10,*,iostat=i) "Hello, world"
end
$ gfortran open+write2.f90
$ ./a.out
Segmentation fault

Same thing with iostat= as with err=.  Without it, things work:
$ cat open+write3.f90
program main
  call system("rm -f asdf.dat; echo foo > asdf.dat; chmod u-w asdf.dat")
  open(file="asdf.dat",unit=10,action="read")
  write(10,*) "Hello, world"
end
$ gfortran open+write3.f90
$ ./a.out
At line 4 of file open+write3.f90
Fortran runtime error: Cannot write to file opened for READ

... which is correct behaviour.

After some poking around, it seems that finalize_transfer()
insists on doing something even if ioparm.library_return
is not equal to LIBRARY_OK.

I've tried out the following patch:

Index: transfer.c
===================================================================
RCS file: /cvsroot/gcc/gcc/libgfortran/io/transfer.c,v
retrieving revision 1.26
diff -c -r1.26 transfer.c
*** transfer.c  15 Jan 2005 08:10:19 -0000      1.26
--- transfer.c  19 Jan 2005 21:26:07 -0000
***************
*** 1383,1388 ****
--- 1383,1391 ----
  static void
  finalize_transfer (void)
  {
+   if (ioparm.library_return != LIBRARY_OK)
+     return;
+
    if ((ionml != NULL) && (ioparm.namelist_name != NULL))
      {
         if (ioparm.namelist_read_mode)

which didn't seem to do any harm (no testcase failures) and
which appears to fix the problem, but I don't know wether this
introduces any cleanup issues.

        Thomas

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Read after a write with a read only file

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-01-19 22:17 -------
Patch:

http://gcc.gnu.org/ml/gcc-patches/2005-01/msg01266.html

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Read after a write with a read only file

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-01-23 02:20 -------
Subject: Bug 19451

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	pbrook@gcc.gnu.org	2005-01-23 02:18:34

Modified files:
	gcc/testsuite  : ChangeLog 
	libgfortran    : ChangeLog 
	libgfortran/io : transfer.c 
Added files:
	gcc/testsuite/gfortran.dg: open_readonly_1.f90 

Log message:
	2005-01-22  Thomas Koenig  <Thomas.Koenig@online.de>
	
	PR libfortran/19451
	* io/transfer.c (finalize_transfer):  Don't do anything if
	there is an error condition.
	* open_readonly_1.f90:  New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4925&r2=1.4926
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gfortran.dg/open_readonly_1.f90.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/ChangeLog.diff?cvsroot=gcc&r1=1.151&r2=1.152
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/io/transfer.c.diff?cvsroot=gcc&r1=1.28&r2=1.29



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Read after a write with a read only file

[Thomas dot Koenig at online dot de]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-01-24 20:03 -------
Fixed.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451

[Bug libfortran/19451] Read after a write with a read only file

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19451