From: Damien Doligez <Damien.Doligez@inria.fr>
To: caml-list@inria.fr
Subject: Re: Is this use of Object.magic safe?
Date: Tue, 14 Nov 2000 15:41:32 +0100 (MET) [thread overview]
Message-ID: <200011141441.PAA0000012997@beaune.inria.fr> (raw)
>From: Stephan Houben <stephan@pcrm.win.tue.nl>
>
>let value_of_int (i : int) : value =
> Obj.magic i
>
>let value_of_allocated_value (av :allocated_value) : value=
> Obj.magic av
>
>let unwrap (int_func : int -> 'a)
> (aval_func : allocated_value -> 'a)
> (v : value) : 'a =
> if Obj.is_int (Obj.repr v)
> then int_func (Obj.magic v)
> else aval_func (Obj.magic v)
>1. Is this safe w.r.t. the garbage collector? Or am I going to confuse the GC?
No problem with the GC.
>2. Can I safely marshall values?
No problem with marshalling either.
>3. Is it worth the trouble? Perhaps O'Caml already does something smart
> when a constructor of the form `Int of int' is encountered?
It doesn't work as you expect because O'Caml is strongly typed, so it
can (and does) use a smart representation for your constant
constructors True and False They are represented as integers, so your
unwrap function cannot tell the difference between a boolean and an
integer. This is typical of the dangers of using Obj.magic.
-- Damien
next reply other threads:[~2000-11-15 21:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-11-14 14:41 Damien Doligez [this message]
-- strict thread matches above, loose matches on Subject: below --
2000-11-13 8:43 Stephan Houben
2000-11-14 21:31 ` Anton Moscal
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