Re: [Caml-list] local root registration

[Xavier Leroy <xavier.leroy@inria.fr>]

> > We've been through several designs for the "local root registration" API.
> > The CAMLxxx macros are the latest design, and the one that we think is
> > the easiest to use.
> 
> I agree that they are easiest if one strictly follows the rules in the
> documentation. However, I would like to point out that there are cases where
> one does not want to do this. In these cases, the older macros (Begin_roots
> and End_roots) are much more flexible, and can even lead to better code.

I agree there are cases where root registration is required only on
rarely-executed paths, and in this case Begin_roots/End_roots allow
avoiding the cost of root registration on other paths.  I haven't
measured how much speed is gained this way.  Probably not much, since
GC root registration is relatively simple.

> I will discuss this a little. Perhaps the Begin_roots/End_roots macros
> should not be deprecated, but left as a low level alternative?

Begin_roots/End_roots will remain defined for a long time, if only
because I still have some old code that use these macros, and (as
regulars on this list know) I don't like gratuitous breaking of old
code.

The only problem with documenting them as a low-level alternative to
CAMLparam is that the chapter "Interfacing Caml with C" of the
documentation is already huge and quite hard to read!  Perhaps a
different organization of this chapter (e.g. a separate chapter for
"Advanced topics in interfacing Caml with C") is in order.

- Xavier Leroy
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