pinning revisited

[Jason O'Brien]

Sean Kelly wrote:
> The Ares GC interface is a tad different from Phobos, and contains 
> pin/unpin methods.  Here's a webpage describing it:
> 
> http://svn.dsource.org/projects/ares/trunk/doc/ares/std/memory.html

I'm glad to see ares has them :) However, from what I could tell it will 
be a while before Ares replaces phobos :(  Adding the dummy functions 
would be very helpful.  (I'd also like to see the pin keyword in the 
language, for reasons almost eerily similiar to the GC vs manual memory 
debate.  It would avoid memory leaks for the common case, which is per 
function pinning.  Also obviously doesn't have any overhead over the 
manual alternative :))

I'd also think a copying collector probably shouldn't collect pinned 
objects, so for compatability this one shouldnt either (by scanning pin 
list for roots). Would make language interop and ownership transfer more 
intuitive (if you temporarily don't want it to move, you probably don't 
want it to be collected in the meantime either).
Could do that yourself of course with addRoot, should work in either 
case, I just think it's less intuitive.  Obviously the overhead of this 
could be avoided if the compiler was pin-aware (you don't need to root C 
function params for example).  Not sure whether it'd hurt performance of 
a noncopying gc, but a copying one could simply search the pin list for 
roots.