From patchwork Tue Sep 21 02:54:11 2010
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Subject: [libgfortran] PR45723 opening /dev/null for appending writes fails
From: Jerry DeLisle <jvdelisle@frontier.com>
X-Patchwork-Id: 65270
Message-Id: <4C981E53.1080608@frontier.com>
To: gfortran <fortran@gcc.gnu.org>
Cc: gcc patches <gcc-patches@gcc.gnu.org>
Date: Mon, 20 Sep 2010 19:54:11 -0700

Hi,

This patch is simple. Test case attached.

Regression tested on x86-64.

OK for trunk?

Jerry

2010-09-20  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	PR libfortran/45723
	* io/open.c (new_unit): On POSITION_APPEND don't seek if file length is
	zero.

! { dg-do run }
! PR45723 opening /dev/null for appending writes fails
logical :: thefile
inquire(file="/dev/null",exist=thefile)
if (thefile) then
  open(unit=7,file="/dev/null",position="append")
  close(7)
endif
end


Index: open.c
===================================================================
--- open.c	(revision 164472)
+++ open.c	(working copy)
@@ -555,7 +555,7 @@ new_unit (st_parameter_open *opp, gfc_unit *u, uni
 
   if (flags->position == POSITION_APPEND)
     {
-      if (sseek (u->s, 0, SEEK_END) < 0)
+      if (file_size (opp->file, opp->file_len) > 0 && sseek (u->s, 0, SEEK_END) < 0)
 	generate_error (&opp->common, LIBERROR_OS, NULL);
       u->endfile = AT_ENDFILE;
     }