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Question about dumping and initialization

From: Jérémie Courrèges-Ang las
Subject: Question about dumping and initialization
Date: Thu, 14 Mar 2013 12:13:27 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (berkeley-unix)

Hi folks,

I'm currently trying to make Emacs use my system's malloc to build 24.3
(my system is OpenBSD).  In order to achieve this, I force
system_malloc=yes in the configure script; the build fails right at
./temacs startup time.

Suspecting a problem with malloc randomization (which is on for all
executables on OpenBSD), I #define USE_LSB_TAG 1, hoping to avoid
pointer mangling.  This works rather well and leads to temacs dumping

Sadly the produced bootstrap-emacs isn't usable and fails with segfaults
in alloc.c.  I'm 99% sure that those segfaults are due to file-global
variables that either:
- aren't reset by temacs at dump time or
- aren't properly re-initialized the dumped bootstrap-emacs executable
(I've used a hack to make emacs reset some of those variables at
startup; each time I re-initialized a new variable, the dumped
executable could run a bit longer.  The first variable that needed this
treatment was src/alloc.c:float_free_list).

I don't know much about Emacs internals but I'd rather go with the
second reason.  I've tested a bit temacs (CANNOT_DUMP=yes in
src/Makefile) and even though it is of course very slow at startup
time, it seems rather stable so far.  Thus I think I'm on the right

So, has any of you already met this problem, and if so, could you please
give me hints about where I should look next?

Thank you for your attention,
Jérémie Courrèges-Anglas - Emacs OpenBSD port maintainer
GPG Key fingerprint: 61DB D9A0 00A4 67CF 2A90  8961 6191 8FBF 06A1 1494

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