rewind.c (st_rewind): Reset unit to read mode.

	* io/rewind.c (st_rewind): Reset unit to read mode.
testsuite/
	* gfortran.dg/rewind_1.f90: New test.

From-SVN: r86659

gcc/testsuite/ChangeLog

+2004-08-27  Paul Brook  <paul@codesourcery.com>
+
+	* gfortran.dg/rewind_1.f90: New test.
+
 2004-08-27  Bud Davis  <bdavis9659@comcast.net>
 
 	PR fortran/16597

gcc/testsuite/gfortran.dg/rewind_1.f90

+! { dg-do run }
+! Check that rewind doesn't delete a file.
+! Writing to the file truncates it at the end of the current record.  Out
+! IO library was defering the actual truncation until the file was rewound.
+! A second rewind would then (incorrectly) think the file had just been
+! written to, and truncate the file to zero length.
+program foo
+  character*11 s
+  open(unit=11, status="SCRATCH")
+  write(11, '(a11)') "Hello World"
+  rewind(11)
+  rewind(11)
+  s = ""
+  read(11, '(a11)') s
+  close(11)
+  if (s .ne. "Hello World") call abort
+end program
+

libgfortran/ChangeLog

+2004-08-27  Paul Brook  <paul@codesourcery.com>
+
+	* io/rewind.c (st_rewind): Reset unit to read mode.
+
 2004-08-27  Bud Davis  <bdavis9659@comcast.net>
 
 	PR fortran/16597

libgfortran/io/rewind.c

@@ -40,8 +40,13 @@ st_rewind (void)
 			"Cannot REWIND a file opened for DIRECT access");
       else
 	{
+	  /* If we have been writing to the file, the last written record
+	     is the last record in the file, so trincate the file now.
+	     Reset to read mode so two consecutive rewind statements
+	     don't delete the file contents.  */
           if (u->mode==WRITING)
             struncate(u->s);
+	  u->mode = READING;
 	  u->last_record = 0;
 	  if (sseek (u->s, 0) == FAILURE)
 	    generate_error (ERROR_OS, NULL);