GNU bug report logs - #8229
possibly uninitialized variable in load_charset

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: bug-gnu-emacs <at> gnu.org
Cc: Kenichi Handa <handa <at> m17n.org>
Subject: possibly uninitialized variable in load_charset
Date: Thu, 10 Mar 2011 16:24:13 -0800

Severity: minor

I found this problem by compiling Emacs with GCC's -Wuninitialized flag.

The following code in the Emacs trunk src/charset.c's load_charset
function is suspicious, because as written it appears that it might be
using an uninitialized variable:

  if (CHARSET_METHOD (charset) == CHARSET_METHOD_MAP)
    map = CHARSET_MAP (charset);
  else if (CHARSET_UNIFIED_P (charset))
    map = CHARSET_UNIFY_MAP (charset);
  if (STRINGP (map))
    ...

The last if-test uses "map", but it's not clear from the previous
tests that "map" must be initialized.

I'm filing a bug report so that someone who is more expert in this
code can take a look at it.  In the meantime, I plan to work around
the problem by replacing:

  else if (CHARSET_UNIFIED_P (charset))
    map = CHARSET_UNIFY_MAP (charset);

with:

  else
    {
      if (! CHARSET_UNIFIED_P (charset))
	abort ();
      map = CHARSET_UNIFY_MAP (charset);
    }

I'm CC'ing this to Kenichi Handa, who committed the code in question.

Message #8 received at 8229 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: 8229 <at> debbugs.gnu.org, 8215 <at> debbugs.gnu.org, 8211 <at> debbugs.gnu.org
Subject: committed the workaround
Date: Wed, 23 Mar 2011 16:19:24 -0700

I committed my abovementioned workaround into the
Emacs trunk on 2011-03-11 (bzr 103589).  I don't
consider this a fix, though, so I'm leaving this
bug report open.

Message #11 received at 8229 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 8211 <at> debbugs.gnu.org, 8229 <at> debbugs.gnu.org, 8215 <at> debbugs.gnu.org
Subject: Re: bug#8229: possibly uninitialized variable in load_charset
Date: Wed, 02 Jun 2021 10:03:14 +0200

Paul Eggert <eggert <at> cs.ucla.edu> writes:

> I committed my abovementioned workaround into the
> Emacs trunk on 2011-03-11 (bzr 103589).  I don't
> consider this a fix, though, so I'm leaving this
> bug report open.

This was ten years ago:

commit 0ac2c2991c1cba4e3c6e5f7b62c7d61b01d69994
Author:     Paul Eggert <eggert <at> cs.ucla.edu>
AuthorDate: Mon Mar 7 16:46:23 2011 -0800
Commit:     Paul Eggert <eggert <at> cs.ucla.edu>
CommitDate: Mon Mar 7 16:46:23 2011 -0800

    * charset.c (load_charset): Abort instead of using uninitialized var.

The code is still pretty much identical, as far as I can tell.  Should
this report be closed now?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #16 received at 8229-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 8229-done <at> debbugs.gnu.org, eggert <at> cs.ucla.edu
Subject: Re: bug#8215: bug#8229: possibly uninitialized variable in
 load_charset
Date: Wed, 02 Jun 2021 15:50:50 +0300

> From: Lars Ingebrigtsen <larsi <at> gnus.org>
> Date: Wed, 02 Jun 2021 10:03:14 +0200
> Cc: 8211 <at> debbugs.gnu.org, 8229 <at> debbugs.gnu.org, 8215 <at> debbugs.gnu.org
> 
> Paul Eggert <eggert <at> cs.ucla.edu> writes:
> 
> > I committed my abovementioned workaround into the
> > Emacs trunk on 2011-03-11 (bzr 103589).  I don't
> > consider this a fix, though, so I'm leaving this
> > bug report open.
> 
> This was ten years ago:
> 
> commit 0ac2c2991c1cba4e3c6e5f7b62c7d61b01d69994
> Author:     Paul Eggert <eggert <at> cs.ucla.edu>
> AuthorDate: Mon Mar 7 16:46:23 2011 -0800
> Commit:     Paul Eggert <eggert <at> cs.ucla.edu>
> CommitDate: Mon Mar 7 16:46:23 2011 -0800
> 
>     * charset.c (load_charset): Abort instead of using uninitialized var.
> 
> The code is still pretty much identical, as far as I can tell.  Should
> this report be closed now?

I'm closing it.  I think non-unified charsets are rarely if ever used
in Emacs these days, but in any case, we have emacs_abort there, so if
the problem ever rears its ugly head, we will catch it.

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