50MB large auto-save file after Emacs crash

50MB large auto-save file after Emacs crash

[Stephen Berman]

A few weeks ago, while using a current CVS build, Emacs suddenly
crashed and vanished without a trace.  At the moment of the crash I
was using Gnus and scrolling an article buffer with the mouse wheel.
Since I was not running under gdb, I couldn't retrieve a backtrace or
anything else to make a useful bug report.  The only remarkable
remnant was the auto-save file: it was 50 megabytes big and glancing
through it, it looked like it contained (at least) the entire buffer
history of the session prior to the crash, in a combination of plain
text and binary or byte-code; perhaps a resident memory dump?  I've
never seen this before and it has not recurred since then (I've also
cvs upped more than once in the mean time), but I wanted to mention
it, in case it rings a bell for anyone.

Steve Berman

Currently
In GNU Emacs 22.0.50.7 (i686-pc-linux-gnu, GTK+ Version 2.8.7)
 of 2005-12-09 on escher
X server distributor `The X.Org Foundation', version 11.0.60802000
configured using `configure '--with-x-toolkit=gtk''

Re: 50MB large auto-save file after Emacs crash

[Eli Zaretskii]

> From: Stephen Berman <Stephen.Berman@gmx.net>
> Date: Fri, 16 Dec 2005 08:27:29 +0100
> 
> A few weeks ago, while using a current CVS build, Emacs suddenly
> crashed and vanished without a trace.  At the moment of the crash I
> was using Gnus and scrolling an article buffer with the mouse wheel.
> Since I was not running under gdb, I couldn't retrieve a backtrace or
> anything else to make a useful bug report.

There could be something else useful on your system: the SYSLOG
files.  It sounds like you are running a Gnu/Linux box, so please look
in the SYSLOG files (if you don't know where or how, please read the
relevant man pages first), and try to find any messages related to the
crashed Emacs session.

Also, please make sure your shell setup doesn't disable core dumps
(with a ulimit command).

In general, if Emacs crashes, it should leave behind a core dump file;
if core files are not disabled, then it's possible that Emacs was
either killed by the OS (thus the advice to look in SYSLOG), or it
simply exited.

Re: 50MB large auto-save file after Emacs crash

[Stephen Berman]

[-- Attachment #1: Type: text/plain, Size: 1684 bytes --]

On Fri, 16 Dec 2005 10:43:05 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <Stephen.Berman@gmx.net>
>> Date: Fri, 16 Dec 2005 08:27:29 +0100
>> 
>> A few weeks ago, while using a current CVS build, Emacs suddenly
>> crashed and vanished without a trace.  At the moment of the crash I
>> was using Gnus and scrolling an article buffer with the mouse wheel.
>> Since I was not running under gdb, I couldn't retrieve a backtrace or
>> anything else to make a useful bug report.
>
> There could be something else useful on your system: the SYSLOG
> files.  It sounds like you are running a Gnu/Linux box, so please look
> in the SYSLOG files (if you don't know where or how, please read the
> relevant man pages first), and try to find any messages related to the
> crashed Emacs session.

Unfortunately, there is nothing unusual in any log file around the
time of the timestamp of the auto-save file, which I assume is close
to the time of the crash.

> Also, please make sure your shell setup doesn't disable core dumps
> (with a ulimit command).

My system is in fact set up not to create core files, but I can change
that.  Can you recommend a reasonable maximum size?

> In general, if Emacs crashes, it should leave behind a core dump file;
> if core files are not disabled, then it's possible that Emacs was
> either killed by the OS (thus the advice to look in SYSLOG), or it
> simply exited.

It appears in this case to be the latter.  FWIW, I still have the
auto-save file, but even compressed it's bigger than 13MB, so I don't
want to attach it.  Anyway, I doubt it's useful, but just to get an
idea of it, I've attached the first 95 lines.

Steve Berman


[-- Attachment #2: first 95 lines of auto-save file --]
[-- Type: application/octet-stream, Size: 10532 bytes --]

[-- Attachment #3: Type: text/plain, Size: 142 bytes --]

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Re: 50MB large auto-save file after Emacs crash

[Eli Zaretskii]

> From: Stephen Berman <Stephen.Berman@gmx.net>
> Date: Fri, 16 Dec 2005 16:28:08 +0100
> 
> > Also, please make sure your shell setup doesn't disable core dumps
> > (with a ulimit command).
> 
> My system is in fact set up not to create core files

So it is plausible that Emacs crashed, but didn't leave a core dump
file behind.  Too bad.

> but I can change that.  Can you recommend a reasonable maximum size?

I recommend `unlimited'.  I'm serious: there's no way to know in
advance how large will be the memory footprint of your Emacs (or any
other program, for that matter) when it crashes.  The core file that
describes a crash is worth its every byte in gold.

> > In general, if Emacs crashes, it should leave behind a core dump file;
> > if core files are not disabled, then it's possible that Emacs was
> > either killed by the OS (thus the advice to look in SYSLOG), or it
> > simply exited.
> 
> It appears in this case to be the latter.

No, I don't think so: if it exited, it would have saved the files, not
leave auto-save files.  I think it crashed.

> FWIW, I still have the
> auto-save file, but even compressed it's bigger than 13MB, so I don't
> want to attach it.  Anyway, I doubt it's useful, but just to get an
> idea of it, I've attached the first 95 lines.

What was the name of the file?

Re: 50MB large auto-save file after Emacs crash

[Stephen Berman]

On Fri, 16 Dec 2005 22:24:40 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <Stephen.Berman@gmx.net>
>> Date: Fri, 16 Dec 2005 16:28:08 +0100
>> 
>> > Also, please make sure your shell setup doesn't disable core dumps
>> > (with a ulimit command).
>> 
>> My system is in fact set up not to create core files
>
> So it is plausible that Emacs crashed, but didn't leave a core dump
> file behind.  Too bad.
>
>> but I can change that.  Can you recommend a reasonable maximum size?
>
> I recommend `unlimited'.  I'm serious: there's no way to know in
> advance how large will be the memory footprint of your Emacs (or any
> other program, for that matter) when it crashes.  The core file that
> describes a crash is worth its every byte in gold.

Ok, I'll give it a try.

>> > In general, if Emacs crashes, it should leave behind a core dump file;
>> > if core files are not disabled, then it's possible that Emacs was
>> > either killed by the OS (thus the advice to look in SYSLOG), or it
>> > simply exited.
>> 
>> It appears in this case to be the latter.
>
> No, I don't think so: if it exited, it would have saved the files, not
> leave auto-save files.  I think it crashed.
>
>> FWIW, I still have the
>> auto-save file, but even compressed it's bigger than 13MB, so I don't
>> want to attach it.  Anyway, I doubt it's useful, but just to get an
>> idea of it, I've attached the first 95 lines.
>
> What was the name of the file?

To my embarrassment, I misidentified the file: it wasn't actually an
auto-save file, but an auto-save-list file; its absolute file name is
/home/steve/.emacs.d/auto-save-list/.saves-931-escher.local.home~

Steve Berman

Re: 50MB large auto-save file after Emacs crash

[Eli Zaretskii]

> From: Stephen Berman <Stephen.Berman@gmx.net>
> Date: Fri, 16 Dec 2005 23:26:37 +0100
> 
> To my embarrassment, I misidentified the file: it wasn't actually an
> auto-save file, but an auto-save-list file; its absolute file name is
> /home/steve/.emacs.d/auto-save-list/.saves-931-escher.local.home~

That figures.  However, only its beginning looked like an
auto-save-list, the rest was just garbage.  I suppose Emacs crashed
before it had a chance to close the file, or else (which sounds more
probable) Emacs data structures were severely corrupted, which both
caused the crash and corrupted the auto-save-list buffer.