Re: foreign objects and the garbage collector

[Tim Meehan]

Thanks Vivien, I had not considered dynamic-wind. I'll look into that a bit
more.

Cheers,
Tim

On Sat, Sep 4, 2021 at 8:35 AM Vivien Kraus <vivien@planete-kraus.eu> wrote:

> Hello,
>
> Le samedi 04 septembre 2021 à 07:41 -0500, Tim Meehan a écrit :
> > I'd rather not compile anything in C, and just use the tools in Guile to
> > interact with libgps. Is there a way to get Guile's garbage collector to
> > call "gps_close" on the opaque structure returned by "gps_open"?
> I think it would be best to do it yourself. Maybe the garbage collector
> will not run immediately (if at all), and if each creation uses "precious"
> resources (such as file descriptors), you might run
> into a shortage before the garbage collector is triggered. This is not
> considered by people writing the C API of course, because they assume you
> would close the thing as soon as possible. (Also, if
> calling the close function is mandatory, for instance to run code that’s
> not just freeing resources, and the garbage collector does not have a
> chance to run, then it’s another problem. However, I
> doubt your library does something like that).
>
> If you want to avoid the problem, you should explicitely bind and call the
> gps-close function and not rely on the garbage collector to do it for you.
> You can use dynamic-wind to open and close
> resources as needed.
>
> That being said, make-pointer (from (system foreign-library)) is probably
> what you are expecting. It should work with gps_close.
>
> Best regards,
>
> Vivien
>
>