Garbage Collection Idea

[Sean Kelly]

Craig Black wrote:
> 
>> Another potential problem is this:
>>
>> # class Foo { ... }
>> # Foo bar = new Foo;
>> # void* quxx = cast(void*)bar;
>>
>> What happens now?  We can no longer tell what type of memory is pointed
>> to by quxx, but we *still* need to scan it.  The only way I can think of
>> to solve this would be to mark each segment of memory with the kind of
>> allocation (class, struct or otherwise), and what the type is.  That, or
>> you can just revert to blind scanning, but then it's no better than the
>> default GC (and more complex code-wise).
> 
> I didn't initially consider this case, but it wouldn't be to hard to 
> accomodate it.  Each allocation unit, whether it is a class instance or not, 
> would have to get an id that describes its identity.

     char** c = cast(char**) malloc( HEIGHT );
     memset( c, 0, HEIGHT );
     gc_addRange( c, c + HEIGHT );

Where would this identity data go?  Another example:

     class C {
         int val;
     }
     int* p;
     {
         C c = new C;
         p = &c.val;
     }

The instance of C must be kept alive because there is a reference to 
it... but to a member element, not the root of the object.



Sean