[gfortran] patch for pr19872

[Bud Davis]

need to truncate a sequential file on the first write, in case it has
more data in it than we are going to write.


no regression i686/gnu/linux.  no changes to NIST test suite.



--bud

2004-02-20  Bud Davis  <bdavis@gfortran.org>

	PR fortran/19872
	* io/transfer.c (data_transfer_init): truncate an existing
        file on the first write.


? gcc/gcc/fortran/.decl.c.swp
Index: gcc/libgfortran/io/transfer.c
===================================================================
RCS file: /cvs/gcc/gcc/libgfortran/io/transfer.c,v
retrieving revision 1.31
diff -c -3 -p -r1.31 transfer.c
*** gcc/libgfortran/io/transfer.c	29 Jan 2005 15:45:17 -0000	1.31
--- gcc/libgfortran/io/transfer.c	20 Feb 2005 02:25:14 -0000
*************** data_transfer_init (int read_flag)
*** 1097,1102 ****
--- 1097,1109 ----
  	generate_error (ERROR_OS, NULL);
      }
  
+   /* Overwriting an existing sequential file ? 
+      it is always safe to truncate the file on the first write */
+   if (g.mode == WRITING 
+       && current_unit->flags.access == ACCESS_SEQUENTIAL 
+       && current_unit->current_record == 0)
+         struncate(current_unit->s); 
+ 
    current_unit->mode = g.mode;
  
    /* Set the initial value of flags.  */





! { dg-do run } 
! PR 19872 - closed and re-opened file not overwriten
      implicit none
      integer i(4)
      data i / 4 * 0 /
      open(1,form='FORMATTED',status='UNKNOWN')
      write(1,'("1 2 3 4 5 6 7 8 9")')
      close(1)
      open(1,form='FORMATTED')
      write(1,'("9 8 7 6")')
      close(1)
      open(1,form='FORMATTED')
      read(1,*)i
      if(i(1).ne.9.and.i(2).ne.8.and.i(3).ne.7.and.i(4).ne.9)call abort
      print*,i
      read(1,*,end=200)i
! should only be able to read one line from the file
      call abort
 200  continue
      close(1,STATUS='DELETE')
      stop
      end