Re: smob gc protection, and inheritance

[Andrew Gaylard <ag@computer.org>]

On 09/04/13 23:13, Ludovic Courtès wrote:
> Hi Doug,
>
> Doug Evans <dje@sebabeach.org> skribis:
>> 3) The docs aren't as clear as they could be on whether the "smob"
>> free function needs to scm_gc_free all results of calls to scm_gc_malloc
>> made when constructing the smob.  IIUC, this is not necessary.
> The ‘scm_gc_free’ function doesn’t need to be called nowadays, because
> the GC automatically frees ‘scm_gc_malloc’ regions when they are no
> longer referenced.
>
> So chances are you don’t even need a SMOB ‘free’ function.
>
>> However, why does the image example do this?
> Indeed, the ‘mark’ and ‘free’ functions in that example could be removed
> altogether, since the only resources associated with the SMOB is memory
> returned by ‘scm_gc_malloc’.
Hi Ludo',

Thanks for this information -- it helps answer my guile-dbi question
(http://lists.gnu.org/archive/html/guile-user/2013-08/msg00133.html).

You say "chances are" -- so when does one need a free() function?
I suspect that guile-dbi does require one, because it has to close
the DB handle; right?

Since the SMOB was allocated with scm_gc_malloc, and since the
things it mark()s are all SCM types, does it follow that it's safe not to
mark() it at all?

Where can I find more information about how guile and its GC work?
In particular, is there a FAQ guide to debugging GC problems?
I'm concerned about leaks, objects collected/freed too early, and
similar bugs.

BTW: all of this is in the context of guile-2.0.9.

Many thanks,

-- 
Andrew