[Python-Dev] sizeof(long) != sizeof(void*)

Samuele Pedroni pedronis at bluewin.ch
Wed Aug 6 23:47:26 EDT 2003

At 22:25 06.08.2003 +0200, Martin v. Löwis wrote:
>Samuele Pedroni <pedronis at bluewin.ch> writes:
> > but that something like id() can be cheaply offered/exposed is very
> > much a characteristic of the underlying GC implementation that is
> > being exploited (objects don't move)
>That is not true. id() exposes the "identity" of an object, and an
>run-time system that has the notion of object identities (as opposed
>to all-things-with-equal-values-are-equal) should have no difficulties
>exposing the object identity as a number.

at each time objects have all different addresses, which does not mean
that an object will not have the same address that some other object, even
still alive, had at some time in the past. Identity distinguishability and
identity as a number are not the same. If you want identity as a number you 
do some work.

> > I have just gone through implementing a correct id() for Jython.
>It sounds like you haven't been looking hard enough. The Java VM
>certainly has a unique (among "life" objects) identification of
>objects, which likely also fits into a fixed number of bytes.

Thanks, I did my homework.

why do you think it certainly have to. It doesn't.

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