Re: [Caml-list] Question about register_global_root

[Jerome Simeon <simeon@research.bell-labs.com>]

On Sun, 2003-06-01 at 15:53, Damien Doligez wrote:
> On Sunday, June 1, 2003, at 12:50 PM, Maas-Maarten Zeeman wrote:
> 
> >  Chris Hecker wrote:
> >
> >>
> >>>  handlers = (value *) malloc(sizeof(value));
> >>>  register_global_root(handlers);
> >>
> >>
> >> Shouldn't you init *handlers to Val_unit before calling 
> >> register_global_root() as well?
> >
> > The manual explicitly tells that register_global_root should be called 
> > before any valid value is stored in it for the first time, like 
> > Val_unit. See Rule 4 of Interfacing C with Objective Caml in the 
> > manual.
> >
> > So I think it is ok the way it is implemented.
> 
> I'm afraid Chris is right and the manual is wrong.
> 

Us poor developers could use a little improvement in the doc in this
area. Some additional example doing this feature in the doc would
help...
- Jerome

> You can store Val_unit before you call register_global_root, because
> Val_unit is not a pointer into the Caml heap.
> You must store a valid value before the first allocation that follows
> register_global_root.
> You can store an allocated value (a pointer into the Caml heap) before
> or after calling register_global_root, but it must be after the last
> allocation that precedes register_global_root, and before the first
> allocation that succeeds it.
> 
> At any rate, storing Val_unit before you call register_global_root is
> safe and does not cost much CPU time.
> 
> -- Damien
-- 
Jerome Simeon <simeon@research.bell-labs.com>
Lucent Technologies

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