GNU bug report logs - #30855
25.3; temacs fails with bus error during garbage collection

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Package: emacs;

Reported by: Ulrich Mueller <ulm <at> gentoo.org>

Date: Mon, 19 Mar 2018 15:25:01 UTC

Severity: normal

Found in version 25.3

Fixed in version 26.1

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

Bug is archived. No further changes may be made.

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Ulrich Mueller <ulm <at> gentoo.org>, Paul Eggert <eggert <at> cs.ucla.edu>
Cc: gentoo-bug <at> opensource.sf-tec.de, 30855 <at> debbugs.gnu.org
Subject: bug#30855: 25.3; temacs fails with bus error during garbage collection
Date: Tue, 20 Mar 2018 16:47:29 +0200

> Date: Tue, 20 Mar 2018 15:00:28 +0100
> Cc: 30855 <at> debbugs.gnu.org,
>     gentoo-bug <at> opensource.sf-tec.de
> From: Ulrich Mueller <ulm <at> gentoo.org>
> 
>   for (pp = start; (void *) pp < end; pp += GC_POINTER_ALIGNMENT)
>     {
>       mark_maybe_pointer (*(void **) pp);
>       mark_maybe_object (*(Lisp_Object *) pp);
>     }
> 
> The loop is in steps of 4 but tries to access objects of size 8.

So you are saying that we should be doing the below instead?

diff --git a/src/alloc.c b/src/alloc.c
index 9d0e2d3..18546ca 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -4983,7 +4983,8 @@ mark_memory (void *start, void *end)
   for (pp = start; (void *) pp < end; pp += GC_POINTER_ALIGNMENT)
     {
       mark_maybe_pointer (*(void **) pp);
-      mark_maybe_object (*(Lisp_Object *) pp);
+      if ((intptr_t) pp % GCALIGNMENT == 0)
+	mark_maybe_object (*(Lisp_Object *) pp);
     }
 }
This bug report was last modified 7 years and 66 days ago.

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