[gclist] conservative vs. "precise" gc

[Darius Blasband]

> 
> It may be worth emphasizing again that there are different possible
> degrees of conservativism with different tradeoffs.  The major possibilities
> are something like:
> 
> 1. Only scan the top activation record conservatively.  Generate stack layout
> descriptors for call sites.  This makes lots of sense to me even if you
> complete control over the compiler.  The main benefit
> is that it allow you to run with a conventional thread system
> (or UNIX signals) without adding
> safe points.  It can also easily be extended to give you better C
> intercallability.  There is some minimal risk of accidental retention.  But
> there are very few systems that don't already include much larger risks
> of this form.
> 
I'd be very interested in any true measure of this risk, and more 
globally, with any measure which relates to where one hopes that
everything will go right, and where everything can go wrong. 
Some people say real problem do not occur in practice very often, 
but what is very often ?

Cheers,

Darius