[Ironruby-core] "Taint" and (internal) copy constructors

Charles Oliver Nutter charles.nutter at sun.com
Thu Oct 25 13:23:35 EDT 2007

Curt Hagenlocher wrote:
> On 10/25/07, *Charles Oliver Nutter* <charles.nutter at sun.com 
> <mailto:charles.nutter at sun.com>> wrote:
>     frozen is another thing entirely, and it has good uses (locking down
>     strings and arrays so they can't be modified, for example). 
> Are extensions not able to ignore "frozen", then?

No, extensions can pretty much do anything they want, which is why they 
suck and why it's nearly impossible for any non-C-based implementation 
to ever support them.

> Other than strings and arrays, it's hard for me to see a compelling 
> reason for this feature.  But then, my thinking is undoubtedly 
> influenced by Python, where strings are immutable and "frozen arrays" 
> are called tuples. :)

Even .NET and Java collection libraries provide ways to get immutable 
collections; it's similar to this. But regardless of whether you think 
it's useful, the important point is below...

> More to the point of this list, though, how can you decide which 
> features of CRuby to ignore?  It can't just be a matter of overhead, 
> because the overhead for "taint" seems to be almost exactly the same as 
> that for "frozen" -- both features require you to keep external 
> bookkeeping information for objects defined outside of Ruby when the 
> feature is used.

You can decide what features to ignore once you know what features are 
needed for existing apps to run. For example...JRuby can run Rails and 
just about anything else that's pure Ruby, so we've been able to 
determine that certain optimizations are safe and certain features can 
be safely "unsupported". It's really, really hard to make that 
determination before you can run nontrivial apps, but you can learn from 

I'd say the only feature we gave up on early was continuations, and I 
actually made a serious effort to support them until we discovered how 
infrequently they were used in the real world. I shall miss my stackless 
interpreter, slow though it was.

- Charlie

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