From: Jeremy Henty <jeremy@...>
Date: 2007-02-19T03:10:08+09:00
Subject: Re: Why should initialize_copy verify the class of the original?

On 2007-02-18, SonOfLilit <sonoflilit@gmail.com> wrote:
> I can call initialize_copy too, here:
>
> object.initialize_copy

Well, actually you *can't*:

    ==>  NoMethodError: private method `initialize_copy' called for ...

:-) but I take your point (and you can work round "private" with
#instance_eval ).  But can it ever be called with an object of the
wrong type unless the user explicitly does so?

> If $SAFE isn't used (which is mostly the case), every bit of code can
> do ANYTHING to the program state.

That's true for Ruby variables, method calls etc., but hopefully we
can ensure the C internals are not corrupted.  I was thinking I could
at least rely on the method being called with objects of the right
type, but as you pointed out that's not true.

> So that initialize_copy sanity test makes sense (personally, I'm not
> sure I would've done it,

I didn't do it either when I implemented color classes for Ruby/FLTK.
I haven't managed to get a segfault out of it, but I can certainly
corrupt objects.  One more for the bug list...

Thanks for the answer, I'm a little embarrassed not to have thought of
it before posting.

Jeremy Henty