Return error when trying to seek a non-seekable buffered file

From-SVN: r174947

libgfortran/ChangeLog

 2011-06-11  Janne Blomqvist  <jb@gcc.gnu.org>
 
+	* io/unix.c (buf_seek): Return error if file is not seekable.
+	(buf_tell): Call buf_seek.
+
+2011-06-11  Janne Blomqvist  <jb@gcc.gnu.org>
+
 	* io/unix.c (fd_to_stream): Figure out if a fd is seekable by
 	trying lseek().
 

libgfortran/io/unix.c

@@ -560,6 +560,11 @@ buf_write (unix_stream * s, const void * buf, ssize_t nbyte)
 static gfc_offset
 buf_seek (unix_stream * s, gfc_offset offset, int whence)
 {
+  if (s->file_length == -1)
+    {
+      errno = ESPIPE;
+      return -1;
+    }
   switch (whence)
     {
     case SEEK_SET:
@@ -585,7 +590,7 @@ buf_seek (unix_stream * s, gfc_offset offset, int whence)
 static gfc_offset
 buf_tell (unix_stream * s)
 {
-  return s->logical_offset;
+  return buf_seek (s, 0, SEEK_CUR);
 }
 
 static int