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


------- 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


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