GNU bug report logs - #3410
tar mode fails to open many valid files

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From: help-debbugs <at> gnu.org (Emacs bug Tracking System)
To: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Subject: bug#3410: marked as done (tar mode fails to open many valid files)
Date: Thu, 04 Jun 2009 21:55:05 +0000

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Your message dated Thu, 04 Jun 2009 16:48:56 -0400
with message-id <jwvprdjlodm.fsf-monnier+emacsbugreports <at> gnu.org>
and subject line Re: bug#3410: tar mode fails to open many valid files
has caused the Emacs bug report #3410,
regarding tar mode fails to open many valid files
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
bug report if necessary, and/or fix the problem forthwith.

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-- 
3410: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=3410
Emacs Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Paul Pogonyshev <p.pogonyshev <at> anakreon.net>
To: submit <at> debbugs.gnu.org
Subject: tar mode fails to open many valid files
Date: Thu, 28 May 2009 17:05:14 +0300

When I open a 'tar.gz' file in Emacs, it quite often fails with a
message similar to:

    File mode specification error: (error
    "ntWorkbookBuilder.SheetRecordCollectingListener.html\"
    title=\"class in org.apache.poi.hssf.eventuserm has size
    -137265917 - corrupted")

E.g. file at

    http://apache.promotionalpro.com/poi/dev/bin/poi-bin-3.5-beta5-20090219.tar.gz

exhibits this error.  It can be extracted without problems with 'tar
-xzf ...' at command line, so it must be a bug in Emacs' tar mode.
Maybe it is too strict or doesn't handle some extension properly.

Paul

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From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Paul Pogonyshev <p.pogonyshev <at> anakreon.net>
Cc: 3410-close <at> debbugs.gnu.org
Subject: Re: bug#3410: tar mode fails to open many valid files
Date: Thu, 04 Jun 2009 16:48:56 -0400

> I.e. it works fine with
>    emacs -Q ~/tmp/poi-bin-3.5-beta5-20090219.tar.gz
> but shows your problem with
>    emacs -Q -f url-handler-mode; C-x C-f http://.../poi... RET

In the end you were right, and I have no idea how I managed to get the
above results.  url-handler-mode makes no difference, and the 64bit
thingy makes a difference (it somehow hides the bug, so it doesn't
signal an error but instead misinterprets the middle of the tar file,
while the beginning and the end are still just fine, so my cursory check
didn't see the corruption).

I've just installed the patch below, which should fix the problem,


        Stefan


--- tar-mode.el.~1.139.~	2009-03-20 16:24:31.000000000 -0400
+++ tar-mode.el	2009-06-04 16:41:49.000000000 -0400
@@ -276,7 +276,10 @@
             (setq link-p 5))            ; directory
 
         (if (and (equal name "././@LongLink")
-                 (equal magic-str "ustar ")) ;OLDGNU_MAGIC.
+                 ;; Supposedly @LongLink is only used for GNUTAR
+                 ;; format (i.e. "ustar ") but some POSIX Tar files
+                 ;; (with "ustar\0") have been seen using it as well.
+                 (member magic-str '("ustar " "ustar\0")))
             ;; This is a GNU Tar long-file-name header.
             (let* ((size (tar-parse-octal-integer
                           string tar-size-offset tar-time-offset))

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