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Re: size of emacs executable after unicode merge

From: Ulrich Mueller
Subject: Re: size of emacs executable after unicode merge
Date: Fri, 21 Nov 2008 15:18:17 +0100

>>>>> Kenichi Handa wrote:

> Currently, I'm running temacs under gdb with this workaround:
> (gdb) set env EMACS_HEAP_EXEC=1

> With this, temacs runs until Fdump_emacs is called (and thus
> I can at least debug loadup.el).  In the call of
> Fdump_emacs, this message is printed:

> **************************************************
> Warning: Your system has a gap between BSS and the
> heap (9475964 bytes).  This usually means that exec-shield
> or something similar is in effect.  The dump may
> fail because of this.  See the section about
> exec-shield in etc/PROBLEMS for more information.
> **************************************************

> and temacs crashes by SIGSEGV.

> Although etc/PROBLEM has this statement:

> You can check the Exec-shield state like this:
>     cat /proc/sys/kernel/exec-shield

> but, my system (debian testing) doesn't have that file.

As far as I know, exec-shield is a feature specific to some RH/Fedora
versions. However, Linux versions 2.6.25 and later implement heap
randomisation, see <http://lkml.org/lkml/2007/10/23/435>.

A possible workaround is to turn heap randomisation off:
| echo -n 1 >/proc/sys/kernel/randomize_va_space


P.S. Gentoo bug 236579 <http://bugs.gentoo.org/236579> contains some
additional information about this.

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