Re: RES: package system modification (module loaders)

[David Jones <drj@...>]

On Jan 18, 2005, at 11:33, duck wrote:

> > I guess things will get even more difficult in 5.1
> > because of the write barrier, however, probably not
> > as bad as managing ref-counting in Python (which is
> > a nightmare ..)
>
> What's a "write barrier"? I have heard of (and felt, alas, in a
> "pedestrian meets bus" incident in Brisbane...boy was that bus in bad
> shape!) the pain barrier and I have heard of (but not seen or felt)
> the barrier reef. But a write barrier...what you get when a
> conference paper has snuck up on you, in my book.

A write barrier is a trap on writing to certain memory locations.  The 
garbage collector uses it to stop the program altering objects that the 
garbage collector has already looked at.  It doesn't really stop it, 
but the garbage collector gets notified, which is good enough.

See http://www.memorymanagement.org/glossary/w.html#write.barrier

David Jones