Hi,
Rather than continuing the GC stuff which seems fruitless I thought it might be better to improve what we have with ref counting (whilst taking a leaf out of the GC book as well).
I note that ref counting is very fast without all the implicit try..finally stuff so I was wondering if it was possible to implement it without them (whilst still being able to free them even if an exception occurs).
My proposal is to do the following (its a hybrid ref count/GC):
1) Remove all implicit try..finally in ref counting.
2) Have a single linked list that contains references to all managed objects (ansi strings, variants etc)
3) Each managed object also has a single linked list that contains addresses of all pointers that reference it.
4) inc ref count means adding the pointer's address to that list
5) dec ref count means removing the pointer's address from that list. When that list is empty the object is freed. (a check for eliminating circular refs should also be done if applicable)
6) Whenever an exception is thrown, wait until its either handled or fully propagated and then perform some garbage collection. (traverse the single linked list of all managed objects and for each object check whether anything that references it is still valid and delete if appropriate).
Im not sure if there are any corner cases where the above would not work but it does have the advantage of being very fast and very efficient memory wise. It also avoids the problem of extended lifetimes that you get with GCs. The only performance hit you will get is when an exception occurs but considering they only occur in exceptional circumstances and that exceptions are slow anyhow I dont think thats any loss. If no exceptions are thrown then no GC needs to be performed ever. Can we get away with doing this?
jamie.
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