GC interpreting integer values as pointers

[Steven Schveighoffer]

On Thu, 14 Oct 2010 12:39:33 -0400, bearophile <bearophileHUGS at lycos.com>  
wrote:

> Steven Schveighoffer:
>
>> There are two problems here.  First, D has unions, so it is impossible  
>> for
>> the GC to determine if a union contains an integer or a pointer.
>
> D has unions, and sometimes normal C-style unions are useful. But in  
> many situations when you have a union you also keep a tag that  
> represents the type, so in many of those situations you may use the  
> tagged union of Phobos, std.variant.Algebraic (if the Phobos  
> implementation is good enough, currently unfinished and not good enough  
> yet) and the D GC may be aware and read and use the tag of an Algebraic  
> union to know at runtime what's the type. This improves the GC precision  
> a little.

Unions are rare enough that I think this may not be worth doing.  But yes,  
it could be had.

-Steve