GNU bug report logs - #25816
Emacs xwidget GC issue with callback

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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: Emacs bug reports and feature requests <bug-gnu-emacs <at> gnu.org>
Cc: Ricardo Wurmus <rekado <at> elephly.net>, Joakim Verona <joakim <at> verona.se>
Subject: Emacs xwidget GC issue with callback
Date: Mon, 20 Feb 2017 09:10:32 -0800

[Message part 1 (text/plain, inline)]

When configuring with --with-xwidgets --enable-check-lisp-object-type the Emacs 
build would fail due to a type confusion in src/xwidget.c, which I attempted to 
fix by installing the attached patch. However, as noted in the patch, this code 
appears to have a garbage-collection bug, as it converts a Lisp_Object to a C 
pointer and stores that pointer (for what appears to be an indefinite period of 
time) into a C object that the garbage collector does not know about. If 
garbage-collection reclaims the object before the callback is used, disaster can 
occur. As I don't know the lifetime of the C object I'm reluctant to try to fix 
this myself, so I'm filing this bug report in the hope that an xwidget expert 
can fix it.

[0001-Port-xwidget-to-DCHECK_LISP_OBJECT_TYPE.txt (text/plain, attachment)]

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