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

[Jess Balint]

Situation #1 - globals:

I have pointers to data that are global (not on the heap). I return these pointers from module functions so that they may be used as parameters to other module function calls. These pointers should *never* be freed. In this case I need to supply a no-op finalizer when creating the user pointer.

Situation #2 - manual memory management:

I have heap-allocated structures whose memory should not be managed by Emacs. I may return pointers to this data one or many times from module calls. The data should be freed only when explicitly requested. I may return many user pointers to the same heap-allocated structure. Even when all these are freed by Emacs, I still retain a pointer in my module which may be returned in a future module call. Again, I'm required to supply a no-op finalizer when creating these user pointers.

Thanks.

Jess

On Tue, Feb 23, 2016 at 9:40 PM, Eli Zaretskii <eliz@gnu.org> wrote:

> Date: Tue, 23 Feb 2016 16:47:12 -0600
> From: Jess Balint <jbalint@gmail.com>
> Cc: 22737@debbugs.gnu.org
>
> If the data is unspecified it doesn't *necessarily* need to be freed. If I return a pointer to some global data then
> I need to create a no-op finalizer just to please this GC code. In some cases I will be managing memory a bit
> more manually and don't care to have Emacs doing anything for me.

I don't think I follow.  How can you manage memory manually when Emacs
does GC whenever it feels like it?  The memory of the objects it GCs
will simply be leaked if you don't have a finalizer.

Can you describe a specific use case where a finalizer would not be
needed?

Thanks.