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bug#22737: 25.1; Finalizer should be optional in dynamic modules


From: Jess Balint
Subject: bug#22737: 25.1; Finalizer should be optional in dynamic modules
Date: Fri, 26 Feb 2016 15:51:43 -0600

On Fri, Feb 26, 2016 at 3:33 PM, Eli Zaretskii <address@hidden> wrote:
> Date: Fri, 26 Feb 2016 12:53:20 -0600
> From: Jess Balint <address@hidden>
> Cc: address@hidden
>
>  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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