Re: Invoking guile procs from C in an efficient way

[Rob Browning]

Victor Morilla <address@hidden> writes:

> Why scm_permanent_object is used ? Would it be
> equivalent something like:
>
> foo()
> {
>   static SCM my_proc =
> scm_variable_ref(scm_c_lookup("my-proc"));
>   scm_apply(my_proc, argslist, SCM_EOL);
> }

It's only OK to cache the result of scm_variable_ref if you know
you'll never change the value of the variable (via set!) and want to
track that change on the C side.

Also, the scm_permanent_object (or something equivalent) is necessary
because the GC can't see static varibles.  However, if you know for
sure that the value you're storing in my_proc is bound to something on
the Scheme side that will outlast your usage of the C code above, then
you can do without the call to scm_permanent_object.

Also, as previously mentioned, you can use
scm_gc_protect/unprotect_object if you only need the object for a
limited period of time.

-- 
Rob Browning
rlb @defaultvalue.org and @debian.org; previously @cs.utexas.edu
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