GC and void*

Steven Schveighoffer schveiguy at yahoo.com
Thu Jan 26 07:38:25 PST 2012

On Wed, 25 Jan 2012 19:11:36 -0500, Nicolas Silva <nical.silva at gmail.com>  

> Hi,
> I need to be sure: would the GC collect an object that is still reachable
> through a void* pointer ?

No.  The current GC does not know anything about type information.  It  
blindly assumes if a pointer points to some block of data, that block of  
data is still in use.

> Also, is there a big difference between casting from Object to T and
> casting from void* to T* ?

Well, first of all, what is T?  If T is a class, you would not cast void *  
to T*, you almost never use T* since T is already a reference.  You could  
cast void * to T.

Casting Object to T if T is a class is going to be a dynamic cast,  
returning null if the object in question is not actually a T.  If you know  
it is a T, then doing a cast to void * first, then to T will circumvent  
the dynamic cast.

> I mean in term of speed. It looks like could be the same difference as
> between C++'s dynamic_cast and static_cast but i'd like to be sure as  
> well.



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