compiler support added for precise GC

[Sean Kelly]

On Apr 16, 2012, at 7:20 PM, Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org> wrote:

> On 4/16/12 1:02 PM, Sean Kelly wrote:
>> As for pointer maps, I think it's reasonable to establish a format
>> that these will be made available to the GC, and for them to come
>> from elsewhere in the runtime.  I realize that different GC
>> implementations may prefer different formats, but hopefully we can
>> settle on one that's pretty generally usable and efficient.  I'd
>> really rather avoid expecting GC writers to know how to meta-process
>> D types to statically generate this themselves.  Moving this into the
>> GC would also eliminate the possibility of having the GC chosen at
>> link-time, which is something that's currently still an option.
> 
> I know you didn't mean it that way, but this gets close enough to a dogma to warrant a protest. "We don't need no steenkin' templates in <sacred area X>" is, I think, an attitude we need to just rid ourselves of. There's the same harm in using templates too much or too little.
> 
> The scheme Walter proposed has a lot of flexibility - it plants one pointer to function per type. This is very flexible because that pointer could point to the same function and use a bitmap-based scheme, or (as Walter proposed) point to different instances of a template that does scanning in a type-specific manner.

Fair enough. How about core.memory?  That's the visible GC interface, and would be where template-based GC methods are defined. It still limits all GC implementations to a single pointer map representation though, without some theatrics.