From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: Dmitry Antipov <dmantipov@yandex.ru>, 12215@debbugs.gnu.org
Subject: bug#12215: CSET is unnecessarily confusing
Date: Thu, 23 Aug 2012 08:26:27 -0400 [thread overview]
Message-ID: <jwvmx1lu7d5.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <50350A4C.5050103@cs.ucla.edu> (Paul Eggert's message of "Wed, 22 Aug 2012 09:35:24 -0700")
> True in both cases. I suppose the notation could grow on one.
Yes, I didn't like it much when I first thought about it, but I'm
beginning to think it's the least bad option (the next one is to use
another preprocessor than cpp ;-).
> Second, why does the setter need the pointer to the start of
> the object, as well as a pointer to the field that's changing?
Depends on how the write barrier works; more specifically, depends on
where the write-barrier writes the "this was modified" info. One choice
is to have a flag in the object (like gcmarkbit) that says "this object
was modified since last scan"; and for that you need a pointer to the
start of the object rather than only to the field.
Of course, there are also many other choices which don't require such
a pointer (e.g. you can add the field's address to a list of "modified
fields"; or you can have a flag covering all objects in a "page", ...).
Stefan
next prev parent reply other threads:[~2012-08-23 12:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-17 0:04 bug#12215: CSET is unnecessarily confusing Paul Eggert
2012-08-17 4:12 ` Dmitry Antipov
2012-08-21 16:55 ` Stefan Monnier
2012-08-22 3:25 ` Paul Eggert
2012-08-22 13:27 ` Stefan Monnier
2012-08-22 16:35 ` Paul Eggert
2012-08-22 16:50 ` Dmitry Antipov
2012-08-23 7:02 ` Paul Eggert
2012-08-23 12:26 ` Stefan Monnier [this message]
2012-08-23 14:40 ` Paul Eggert
2012-08-24 3:46 ` Chong Yidong
2012-08-24 3:57 ` Paul Eggert
2012-08-24 4:26 ` Dmitry Antipov
2012-08-24 15:10 ` Stefan Monnier
2012-08-24 17:19 ` Paul Eggert
2012-08-24 17:27 ` Tom Tromey
2012-08-24 18:11 ` Paul Eggert
2012-08-24 21:12 ` Stefan Monnier
2012-08-25 0:17 ` Paul Eggert
2012-08-25 1:58 ` Stefan Monnier
2012-08-26 5:05 ` Paul Eggert
2012-08-21 17:55 ` Stefan Monnier
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