[Patch, libfortran, committed] Return error when trying to seek a non-seekable buffered file

[Patch, libfortran, committed] Return error when trying to seek a non-seekable buffered file

[Janne Blomqvist]

Hi,

In libgfortran, buffered and unbuffered IO should work the same except
for the buffering. For the unbuffered IO, seek and tell operations
reduce to calls to lseek(). Thus, if the file is not seekable, they
return -1 and set errno. Or strictly speaking, POSIX says that lseek()
on a non-seekable file is implementation-dependent, but AFAIK most
implementations return error. The attached patch makes buffered IO
behave the same.

Regtested on x86_64-unknown-linux-gnu, committed as obvious.


Index: ChangeLog
===================================================================
--- ChangeLog   (revision 174946)
+++ ChangeLog   (working copy)
@@ -1,5 +1,10 @@
 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().

Index: io/unix.c
===================================================================
--- io/unix.c   (revision 174946)
+++ io/unix.c   (working copy)
@@ -560,6 +560,11 @@ buf_write (unix_stream * s, const void *
 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 of
 static gfc_offset
 buf_tell (unix_stream * s)
 {
-  return s->logical_offset;
+  return buf_seek (s, 0, SEEK_CUR);
 }

 static int


-- 
Janne Blomqvist