Faster Virtual Method Dispatch

[Mike Capp]

In article <e2mfjd$1f3d$1 at digitaldaemon.com>, Walter Bright says...
>
>True, but shared_ptr<> is billed as the C++ answer to gc, and 
>shared_ptr<> is not intrusive.

Shrug. I'm finding myself increasingly unconcerned these days with what's
"billed as the C++ answer". I mean, iostreams?

>> Refcount twiddling is only needed when changing an
>> "owning" pointer, plus the rare "safety" case 

>But that means just going back to the old way of being very, very 
>careful about who "owns" the pointer and who doesn't. Refcounting is 
>supposed to eliminate that nuisance.

I'm not sure that's true. Smartpointer refcounting is supposed to make ownership
rules explicit in code where they can be a) seen and b) automated, instead of
hidden in documentation.

In practice, I still make daft array-overrun and fencepost errors from time to
time, but I've never had a problem with refcounting and ownership. As a first
approximation: member variables, globals and new'ed locals are owners, and
everything else isn't. Exceptions to this rule (e.g. double-linked lists) tend
to be glaringly obvious.

>Sure you could do that, but then slices and shared_ptr's are not 
>interchangeable.

True, but again, I'm not especially interested in shared_ptr, and this isn't a
fundamental problem - you can write intrusive interchangeable string and slice
classes in C++. 

>> Has there ever been a language that successfully combined 
>> compacting GC with raw pointers? How would this work? 
>
>Oh, it's quite doable <g>.

I find your ideas intriguing, and would like to subscribe to your newsletter.

Can you elaborate, or is this a trade secret?

cheers
Mike