[Bug libfortran/46373] New: fflush called when reading from a string

[Bug libfortran/46373] New: fflush called when reading from a string

[e01reynier at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

           Summary: fflush called when reading from a string
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: e01reynier@gmail.com


When reading a integer from a string (ie READ(string,'(I3)') number) it calls
fflush from flush_if_preconnected routine inside data_transfer_init routine.
It causes me trouble in a C thread waiting for keyboard calling getc.
Is there a valid reason for calling fflush while reading a string ?

[Bug libfortran/46373] fflush called when reading from a string

[kargl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2010.11.08 17:05:08
                 CC|                            |kargl at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from kargl at gcc dot gnu.org 2010-11-08 17:05:08 UTC ---
See the documentation that comes with gfortran.

You can use 

* GFORTRAN_UNBUFFERED_ALL:: Don't buffer I/O for all units.
* GFORTRAN_UNBUFFERED_PRECONNECTED:: Don't buffer I/O for preconnected units.

to control the buffering of IO.

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jvdelisle at gcc dot
                   |                            |gnu.org

--- Comment #2 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-08 17:47:14 UTC ---
An internal unit fflush is:

static int
mem_flush (unix_stream * s __attribute__ ((unused)))
{
  return 0;
}

So I don't think this is your issue.

Maybe something else?

[Bug libfortran/46373] fflush called when reading from a string

[e01reynier at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #3 from e01reynier at gmail dot com 2010-11-09 07:50:37 UTC ---
(In reply to comment #1)
> See the documentation that comes with gfortran.
> 
> You can use 
> 
> * GFORTRAN_UNBUFFERED_ALL:: Don't buffer I/O for all units.
> * GFORTRAN_UNBUFFERED_PRECONNECTED:: Don't buffer I/O for preconnected units.
> 
> to control the buffering of IO.

I try under bash with:
  export GFORTRAN_UNBUFFERED_ALL=y
or
  export GFORTRAN_UNBUFFERED_PRECONNECTED=y
but fflush is always called when I read from a string.

Anyway reading from a string has nothing to do with buffered I/O !
Why the hell is fflush called ?

[Bug libfortran/46373] fflush called when reading from a string

[e01reynier at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #4 from e01reynier at gmail dot com 2010-11-09 07:54:58 UTC ---
(In reply to comment #2)

> An internal unit fflush is:

Is there really an internal unit involved when reading an integer from a string
?

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jvdelisle at gcc dot
                   |gnu.org                     |gnu.org

--- Comment #5 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-09 13:22:15 UTC ---
In Fortran, by definition, "internal unit" is a character string. Libgfortran
defines a common I/O interface.  During initialization of an I/O call, the
appropriate functions are mapped via function pointers so that when the
read/write statements are executed, either the external unit (file) routines or
internal unit (string) routines are invoked.

Regardless, I misunderstood your original post.  I will commit the following
obvious patch after regression testing. At least the code lived up to its
comment.  ;)

Index: libgfortran/io/transfer.c
===================================================================
--- libgfortran/io/transfer.c    (revision 166469)
+++ libgfortran/io/transfer.c    (working copy)
@@ -2646,7 +2646,8 @@
     }

   /* Bugware for badly written mixed C-Fortran I/O.  */
-  flush_if_preconnected(dtp->u.p.current_unit->s);
+  if (!is_internal_unit (dtp))
+    flush_if_preconnected(dtp->u.p.current_unit->s);

   dtp->u.p.current_unit->mode = dtp->u.p.mode;

[Bug libfortran/46373] fflush called when reading from a string

[e01reynier at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #6 from e01reynier at gmail dot com 2010-11-09 13:39:33 UTC ---
It should solve my problem.
Thanks a lot !

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #7 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-09 13:52:03 UTC ---
Author: jvdelisle
Date: Tue Nov  9 13:51:57 2010
New Revision: 166490

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166490
Log:
2010-11-09  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

    PR libgfortran/46373
    * io/transfer.c (data_transfer_init): Do not call flush_if_preconnected
    if this is an internal unit.

Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/io/transfer.c

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #8 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-09 22:12:07 UTC ---
Aside from Janne's comments about getting rid of this function completely, I
think the little fix is a candidate for back port to 4.4 and 4.5. What do you
think Janne?

[Bug libfortran/46373] fflush called when reading from a string

[e01reynier at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #9 from e01reynier at gmail dot com 2010-11-10 08:13:54 UTC ---
(In reply to comment #8)
> Aside from Janne's comments about getting rid of this function completely, I
> think the little fix is a candidate for back port to 4.4 and 4.5. What do you
> think Janne?

It would be nice.

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #10 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-11 03:12:39 UTC ---
Author: jvdelisle
Date: Thu Nov 11 03:12:35 2010
New Revision: 166588

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166588
Log:
2010-11-10  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

    PR libgfortran/46373
    Backport from mainline:
    * io/transfer.c (data_transfer_init): Do not call flush_if_preconnected
    if this is an internal unit.

Modified:
    branches/gcc-4_5-branch/libgfortran/ChangeLog
    branches/gcc-4_5-branch/libgfortran/io/transfer.c

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

--- Comment #11 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-11 03:24:29 UTC ---
Author: jvdelisle
Date: Thu Nov 11 03:24:26 2010
New Revision: 166589

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166589
Log:
2010-11-10  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

    PR libgfortran/46373
    Backport from mainline:
    * io/transfer.c (data_transfer_init): Do not call flush_if_preconnected
    if this is an internal unit.

Modified:
    branches/gcc-4_4-branch/libgfortran/ChangeLog
    branches/gcc-4_4-branch/libgfortran/io/transfer.c

[Bug libfortran/46373] fflush called when reading from a string

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46373

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #12 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> 2010-11-11 03:28:54 UTC ---
Fixed on 4.4 and 4.5 and closing