At the moment, Debugger provides a number of functions whose behavior depends on the relative timing of GC. This makes for confusion and sadness; these APIs should be redesigned. Off the top of my head: - Debugger.prototype.getDebuggees returns only the remaining live debuggees; a Debugger instance doesn't hold strong references to its debuggees. I don't even think this function is used, except by tests! - Debugger.prototype.findScripts is horribly GC-sensitive. See bug 944258 and bug 944260. - Debugger.prototype.findAllGlobals is also GC-sensitive. I don't even think it's used any more. We have alternatives to all these, so there's no excuse. Let's make this a meta-bug for all work to remove such behaviors.

Oh boy... I wish I'd seen this sooner. Explains a lot of the weirdness I see (not least bug 901930)