[Vm-dev] How to addGCRoot: ? help requested

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Sun Dec 23 21:25:59 UTC 2012

Ah OK, thanks, I get it...
Two questions remain:

1) how to access addGCroot: from within a SmartSyntaxInterpreterPlugin ?
2) when do you need to register (re-register)?
- once at image startup ?
- after each snapshot ?

I think I'll have a look at NativeBoost indeed...


2012/12/23 Igor Stasenko <siguctua at gmail.com>:
> addGCRoot()
> takes a pointer to some memory location, where root object will be stored.
> sqInt * mem;
> mem = malloc(4);
> *mem = someOop;
> addGCRoot(mem);
> now, to read a reference to 'someObject' at any place you can just do
> someOop = *mem.
> often you may want to register multiple objects for use.
> you can , of course, use addGCRoot() per each of them,
> or, just use an array to store unlimited number of objects as roots
> (that way you don't risk overflowing extra roots table, as well as can manage
> that array at image side, and at cost of extra indirection).
> If you want a working example you can look at NBExtraRootsRegistry
> implementation,
> which is part of NativeBoost, how i using it.
> On 23 December 2012 21:34, Nicolas Cellier
> <nicolas.cellier.aka.nice at gmail.com> wrote:
>> I wanted to experiment a plugin and need to register a couple of
>> classes that some primitive will test/instantiate.
>> The ugly way is to pollute specialObjectArray...
>> But #recreateSpecialObjectsArray recommend using addGCRoot()
>> Fine, I'd like to try.
>> What I'd like to do is register my couple of classes in a
>> primRegister() primitive
>> (once for all or at each image startup, or at each snapshot, whatever...)
>> Then to later use the registered classes in primDoSomething().
>> I can see ObjectMemory>>addGCRoot: but unfortunately, absolutely no
>> sender of it to serve as an example...
>> I even don't know how to access the objectMemory from within a
>> SmartSyntaxInterpreterPlugin ?
>> I can only see a interpreterProxy and
>> Then how to retrieve my registered objects? they are store in the
>> extraRoots at some index, but that index is not returned by
>> addGCRoot:...
>> Anyway, the index could change thanks to removeGCRoot:, so I'm stuck here...
>> I must be missing something...
>> Or maybe addGCRoot: is just here to prevent an Object to be garbage
>> collected but does not really offer a registering service...
>> If you know about any documentation/example hanging around or have
>> some clues I'll be happy that you share them !
>> Last note, I'm in a VMMaker oscog flavour...
>> Nicolas
> --
> Best regards,
> Igor Stasenko.

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