* bug#8496: some file locking code in insert-file-contents cannot be right
@ 2011-04-14 0:40 Paul Eggert
2011-04-14 6:48 ` Eli Zaretskii
2011-04-14 8:00 ` Andreas Schwab
0 siblings, 2 replies; 6+ messages in thread
From: Paul Eggert @ 2011-04-14 0:40 UTC (permalink / raw)
To: 8496
As a result of the "mark unexported symbols 'static'" patch that I'm
working on, in the Emacs trunk I found some file-locking code inside
insert-file-contents that cannot be right:
if (NILP (visit) && inserted > 0)
{
#ifdef CLASH_DETECTION
if (!NILP (BVAR (current_buffer, file_truename))
/* Make binding buffer-file-name to nil effective. */
&& !NILP (BVAR (current_buffer, filename))
&& SAVE_MODIFF >= MODIFF)
we_locked_file = 1;
#endif /* CLASH_DETECTION */
prepare_to_modify_buffer (GPT, GPT, NULL);
}
The above code is equivalent to a no-op, since 'inserted' must
be zero here. There's later code:
#ifdef CLASH_DETECTION
if (we_locked_file)
unlock_file (BVAR (current_buffer, file_truename));
#endif
that is also a no-op, because 'we_locked_file' must be zero.
GCC merrily optimizes all this code away, but I don't think
that was intended. What *is* intended here?
^ permalink raw reply [flat|nested] 6+ messages in thread
* bug#8496: some file locking code in insert-file-contents cannot be right
2011-04-14 0:40 bug#8496: some file locking code in insert-file-contents cannot be right Paul Eggert
@ 2011-04-14 6:48 ` Eli Zaretskii
2011-04-14 7:53 ` Paul Eggert
2011-04-14 8:55 ` Eli Zaretskii
2011-04-14 8:00 ` Andreas Schwab
1 sibling, 2 replies; 6+ messages in thread
From: Eli Zaretskii @ 2011-04-14 6:48 UTC (permalink / raw)
To: Paul Eggert; +Cc: 8496
> Date: Wed, 13 Apr 2011 17:40:49 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
>
> As a result of the "mark unexported symbols 'static'" patch that I'm
> working on, in the Emacs trunk I found some file-locking code inside
> insert-file-contents that cannot be right:
>
> if (NILP (visit) && inserted > 0)
> {
> #ifdef CLASH_DETECTION
> if (!NILP (BVAR (current_buffer, file_truename))
> /* Make binding buffer-file-name to nil effective. */
> && !NILP (BVAR (current_buffer, filename))
> && SAVE_MODIFF >= MODIFF)
> we_locked_file = 1;
> #endif /* CLASH_DETECTION */
> prepare_to_modify_buffer (GPT, GPT, NULL);
> }
>
> The above code is equivalent to a no-op, since 'inserted' must
> be zero here.
In Emacs 21.4a, the corresponding code was this:
if (!NILP (visit))
{
...
#ifdef CLASH_DETECTION
if (NILP (handler))
{
if (!NILP (current_buffer->file_truename))
unlock_file (current_buffer->file_truename);
unlock_file (filename);
}
#endif /* CLASH_DETECTION */
The change to the present form was between 21.4a and 22.1. It appears
in the trunk history as part of a huge merge from a branch, probably
the Emacs 22.1 release branch. I need more forensic work to find out
why the change was made, but at this point it certainly looks like
someone goofed with the condition.
What platforms use CLASH_DETECTION?
^ permalink raw reply [flat|nested] 6+ messages in thread
* bug#8496: some file locking code in insert-file-contents cannot be right
2011-04-14 6:48 ` Eli Zaretskii
@ 2011-04-14 7:53 ` Paul Eggert
2011-04-14 8:07 ` Eli Zaretskii
2011-04-14 8:55 ` Eli Zaretskii
1 sibling, 1 reply; 6+ messages in thread
From: Paul Eggert @ 2011-04-14 7:53 UTC (permalink / raw)
To: Eli Zaretskii; +Cc: 8496
On 04/13/2011 11:48 PM, Eli Zaretskii wrote:
> What platforms use CLASH_DETECTION?
According to the .h files,
pretty much all the POSIXish platforms do it
(GNU/Linux, BSD, MacOS, AIX, etc.)
and it's also done on Cygwin.
^ permalink raw reply [flat|nested] 6+ messages in thread
* bug#8496: some file locking code in insert-file-contents cannot be right
2011-04-14 0:40 bug#8496: some file locking code in insert-file-contents cannot be right Paul Eggert
2011-04-14 6:48 ` Eli Zaretskii
@ 2011-04-14 8:00 ` Andreas Schwab
1 sibling, 0 replies; 6+ messages in thread
From: Andreas Schwab @ 2011-04-14 8:00 UTC (permalink / raw)
To: Paul Eggert; +Cc: 8496-done
Paul Eggert <eggert@cs.ucla.edu> writes:
> What *is* intended here?
If you look at 9a95c4d it is obvious.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
^ permalink raw reply [flat|nested] 6+ messages in thread
* bug#8496: some file locking code in insert-file-contents cannot be right
2011-04-14 7:53 ` Paul Eggert
@ 2011-04-14 8:07 ` Eli Zaretskii
0 siblings, 0 replies; 6+ messages in thread
From: Eli Zaretskii @ 2011-04-14 8:07 UTC (permalink / raw)
To: Paul Eggert; +Cc: 8496
> Date: Thu, 14 Apr 2011 00:53:17 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> CC: 8496@debbugs.gnu.org
>
> On 04/13/2011 11:48 PM, Eli Zaretskii wrote:
> > What platforms use CLASH_DETECTION?
>
> According to the .h files,
> pretty much all the POSIXish platforms do it
> (GNU/Linux, BSD, MacOS, AIX, etc.)
> and it's also done on Cygwin.
That's what I thought. I guess that pretty much excludes the
possibility that this went undetected because no one uses it.
^ permalink raw reply [flat|nested] 6+ messages in thread
* bug#8496: some file locking code in insert-file-contents cannot be right
2011-04-14 6:48 ` Eli Zaretskii
2011-04-14 7:53 ` Paul Eggert
@ 2011-04-14 8:55 ` Eli Zaretskii
1 sibling, 0 replies; 6+ messages in thread
From: Eli Zaretskii @ 2011-04-14 8:55 UTC (permalink / raw)
To: eggert, 8496
> Date: Thu, 14 Apr 2011 02:48:28 -0400
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 8496@debbugs.gnu.org
> Reply-To: Eli Zaretskii <eliz@gnu.org>
>
> > if (NILP (visit) && inserted > 0)
> > {
> > #ifdef CLASH_DETECTION
> > if (!NILP (BVAR (current_buffer, file_truename))
> > /* Make binding buffer-file-name to nil effective. */
> > && !NILP (BVAR (current_buffer, filename))
> > && SAVE_MODIFF >= MODIFF)
> > we_locked_file = 1;
> > #endif /* CLASH_DETECTION */
> > prepare_to_modify_buffer (GPT, GPT, NULL);
> > }
> >
> > The above code is equivalent to a no-op, since 'inserted' must
> > be zero here.
>
> In Emacs 21.4a, the corresponding code was this:
>
> if (!NILP (visit))
> {
> ...
> #ifdef CLASH_DETECTION
> if (NILP (handler))
> {
> if (!NILP (current_buffer->file_truename))
> unlock_file (current_buffer->file_truename);
> unlock_file (filename);
> }
> #endif /* CLASH_DETECTION */
Sorry, that was wrong. The previous version was this:
if (NILP (visit) && total > 0)
prepare_to_modify_buffer (PT, PT, NULL);
The ChangeLog entry for the change (in revision 62259) is this:
(Finsert_file_contents): If we read 0 bytes from a special file,
unlock the visited file if we locked it.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2011-04-14 0:40 bug#8496: some file locking code in insert-file-contents cannot be right Paul Eggert
2011-04-14 6:48 ` Eli Zaretskii
2011-04-14 7:53 ` Paul Eggert
2011-04-14 8:07 ` Eli Zaretskii
2011-04-14 8:55 ` Eli Zaretskii
2011-04-14 8:00 ` Andreas Schwab
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