Re: Copying one Lisp_Object to another in C code?

[Ken Raeburn <raeburn@raeburn.org>]

On Jul 1, 2010, at 20:18, James Cloos wrote:
> Given:
> 
>    static void (foo)
>        Lisp_Object foo;
>    {
>        Lisp_Object bar;
>    /* etc */
> 
> is it OK to do:
> 
>        bar = foo;
> 
> or is there a function or macro one should call?

Simple assignments are done all over the place currently.  It would take some drastic reworking if some macro invocation were to become necessary.

> I presume GCPRO1 (foo) is in order either way?

Depending on the details of your usage, yes.  (If the value is always stored in other places where the version of the GC system that doesn't scan the entire stack and register set automatically will be able to find it, at any of the points where the GC system can be invoked, then you don't need an explicit GCPRO.  But then you have to understand where the old GC scanner will look, and when it can get invoked.)  Just being conservative about it shouldn't hurt, either.

Ken