GNU bug report logs - #22737
25.1; Finalizer should be optional in dynamic modules

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Message #29 received at 22737 <at> debbugs.gnu.org (full text, mbox):

From: Jess Balint <jbalint <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Daniel Colascione <dancol <at> dancol.org>, 22737 <at> debbugs.gnu.org,
 John Wiegley <johnw <at> gnu.org>
Subject: Re: bug#22737: 25.1; Finalizer should be optional in dynamic modules
Date: Fri, 26 Feb 2016 15:51:43 -0600

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On Fri, Feb 26, 2016 at 3:33 PM, Eli Zaretskii <eliz <at> gnu.org> wrote:

> > Date: Fri, 26 Feb 2016 12:53:20 -0600
> > From: Jess Balint <jbalint <at> gmail.com>
> > Cc: 22737 <at> debbugs.gnu.org
> >
> >  What will happen if such objects are exposed to Lisp, copied or
> >  assigned to other Lisp variables, etc.? Won't this cause all kinds of
> >  trouble, like modifying one such object will magically modify several
> >  others, which share its storage?
> >
> > This is how C code works. If you return a pointer from a function, you
> may have to free that pointer yourself or
> > you may not. You may get the same pointer back from multiple calls to
> the same function. If you use the
> > pointer after it's been freed, it's your problem. You need to agree with
> the owner of the pointer how the
> > memory is to be managed. With pointers, modifications to the underlying
> data are visible by all who have a
> > pointer to the data. I wouldn't call this "magically modifying others".
>
> In C, yes.  But we are talking about Lisp objects here.
>
> Am I the only one who is uneasy with supporting such Lisp objects?  If
> so, I will shut up and install the changes.  Daniel, John, what's your
> opinion on this?
>
> Thanks.
>

All I'm asking for is to allow the code to accept a NULL finalizer. This
means no finalizer will be called. It's a clear and simple semantic. Upside
is that I (and others who do not want Emacs to free their pointers) will
not have to create a no-op function unnecessarily to supply a finalizer to
Emacs.

Thanks.

Jess

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