GC changes

[Jamie Lokier]

dewar@gnat.com wrote:
> <<Actually there is another approach.  You could generate unwind stubs
> similar to exception handling, with a table indexed by program counter
> to the stubs.  For most program addresses the stub would be empty, but
> for certain places where only an offset address is present, the stub
> would generate the non-offset address.
> 
> This has the advantage that no optimisation is penalised.  It's quite
> complex to implement though.
> >>
> 
> Well it's a step along the route to type accurate GC, and really if you
> even contemplate going this far, you may as well go all the way.

Sometimes you don't have accurate types.  E.g. you may still want a
Boehm-style conservative GC to emulate malloc() for C programs, and the
type information in those C programs is not accurate enough for typed GC.

However I agree it would be very nice to do full type accurate GC.
_Much_ more stub code & tables though.

-- Jamie