Subj : Garbage Collection Woes
To   : netscape.public.mozilla.jseng
From : "Stephen Jones" <Stephen@Jones-net.com>
Date : Fri Apr 25 2003 01:32 pm

I thought I had Garbage Collection in SpiderMonkey figured out, but it turns
out I was wrong and I can't figure it out to save my life. I've read all the
old posts to this newsgroup regarding Garbage Collection, all the GC tips on
the web I can find and it seems to make sense, but it doesn't work and I
can't figure out what I'm doing wrong.

I was just using JS_AddNamedRoot for everything, but it turns out that
doesn't work for (probably) obvious reasons. If you have multiple objects
that are using the same object and one goes out of scope and removes the
root, then that object is unprotected.

From what I understand, basically, you are supposed to protect object froms
GC by setting them as properties on other protected objects. Please correct
me if I'm wrong.

So, I have a root object that I "attach" to the global object using
JS_DefineProperty (I assume that this protects this object, I can't tell
because I have AddRoots everywhere . . . I'm trying to understand this so I
can clean it up). This root object has various properties (defined using
tiny ids on the prototype of the root object) that are JSObjects as well.
After an object is instantiated from the prototype (JS_NewObject), to
protect these objects from GC, I call JS_SetProperty passing in the
JSObject. This does not work, especially for read-only properties. If I run
GC at this point, these objects are destroyed. Note: if I first retrieve the
property, then run GC, it is not garbage collected (maybe this is because it
is stored in a local root for the return value of the getter?)

Anyway, can someone please set me straight? How should this work? What am I
missing?

Thanks,
- S

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