From: daz <dooby@...10.karoo.co.uk>
Date: 2004-03-07T23:34:41+09:00
Subject: Re: freeze, frozen? in extensions


Tim Hunter wrote:
> I'm poking around in the 1.8.1 ext/ sources and I notice that there are
> very, very few uses of rb_check_frozen. I expected to see the C extensions
> calling rb_check_frozen before modifying them. What am I overlooking? Is
> it just not necessary?



Calling a C extension which uses rb_str_modify() and /not/ rb_check_frozen_p()
on a string that's frozen before the call  gives:

D:/ruby/DfB/rb6062.TMP:3:in `call': can't modify frozen string (TypeError)

No reason why that should be expected, though.
You could have two exts that do the same job -- one causing a TypeError,
but not the other.

As a Ruby String points to a C string, it would easily be possible for
an ext just to overwrite part of the C string even if it had been frozen
but (you made me think) Ruby objects *always* are/should be modified via
the API rather than directly which allows Ruby to check things such as
/frozen/ status.

That may be a rule which just *feels* right to my narrow experience.
If I learned it, it was only a few moments ago.
I'd retract it if someone offered the glaring exception(s) :)


daz