Re: GC and simple smobs??

[Jean Abou Samra]

Le 17/06/2022 à 23:49, David Kastrup a écrit :
> Jean Abou Samra <jean@abou-samra.fr> writes:
>
> > By the way, I have a side question. Suppose I have determined
> > that I need to mark the local variable scm_obj with
> > scm_remember_upto_here in this code:
> >
> > SCM scm_obj = get_it_from_somewhere ();
> >
> > return something_that_needs_scm_obj_alive;
> >
> > // Is this correct?
> > scm_remember_upto_here (scm_obj);
> >
> >
> > Might the compiler detect that return exits the function and
> > ignore the scm_remember_upto_here?
> return; releases the stack frame.  "return
> something_that_needs_scm_obj_alive;" is not a valid pattern unless the
> returned value itself is an SCM that will cover scm_obj in its GC scope.



Well, I was thinking of something like this:

Pitch *p = unsmob<Pitch> (scm_pitch);
return *p;
scm_remember_upto_here (scm_pitch); // ??

where I thought GC could happen between 'unsmob<Pitch>' and
'return *p', making p a dangling pointer. If you are correct
about GC only being triggered upon (Guile) allocations, that
wouldn't be a concern.