Re: building/using address-sanitizer-enabled emacs?

[Paul Eggert <eggert@cs.ucla.edu>]

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On 05/17/2017 09:06 AM, Eli Zaretskii wrote:
> I think we might be talking about 2 different reports. I meant the
> one here:
>
>    http://lists.gnu.org/archive/html/emacs-devel/2017-05/msg00246.html

Ah, that came after his original report 
<http://lists.gnu.org/archive/html/emacs-devel/2017-05/msg00182.html>, 
which is the one I was referring to. I reproduced the later problem, and 
as near as I can make it out it is due to an incompatibility between 
vfork and -fsanitize=address. My guess is that the vforked child 
corrupts the parent's shadow memory. I worked around the problem by 
installing the attached patch into Emacs.

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From 709259dcc501ef991991a35a6ffb2aef02a62c60 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 17 May 2017 10:58:11 -0700
Subject: [PATCH] Work around AddressSanitizer bug with vfork
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Problem reported by Jim Meyering in:
http://lists.gnu.org/archive/html/emacs-devel/2017-05/msg00246.html
* src/conf_post.h (vfork) [ADDRESS_SANITIZER]: Define to fork.
Unfortunately with the AddressSanitizer in Fedora 25 x86-64, the
vforked child messes up the parent’s shadow memory.  This is too
bad, as we’d rather have AddressSanitizer catch memory-access bugs
related to vfork.
---
 src/conf_post.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/conf_post.h b/src/conf_post.h
index 4fc0428..1462bd1 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -302,6 +302,12 @@ extern int emacs_setenv_TZ (char const *);
 # define ATTRIBUTE_NO_SANITIZE_ADDRESS
 #endif
 
+/* gcc -fsanitize=address does not work with vfork in Fedora 25 x86-64.
+   For now, assume that this problem occurs on all platforms.  */
+#if ADDRESS_SANITIZER && !defined vfork
+# define vfork fork
+#endif
+
 /* Some versions of GNU/Linux define noinline in their headers.  */
 #ifdef noinline
 #undef noinline
-- 
2.9.4