Interfaces for observing the cycle collector’s work, both from C++ and
from JavaScript.
If given an object implementing nsICycleCollectorListener, the cycle
collector calls that object’s methods as it works, describing the
objects it visits, the edges it finds, and the conclusions it reaches
about which objects are live.
Analyzing cycle collection from JS is harder: an nsICycleCollectorListener
mustn’t mess with the object graph while the cycle collector is trying to
figure it out, which means it can’t be implemented by JS code: JS can’t do
much of anything useful within those constraints. Instead, JS code can
instantiate @mozilla.org/cycle-collector-logger;1, a C++ class implementing
nsICycleCollectorListener that logs the cycle collector’s mumblings and then
replays them later to an nsICycleCollectorHandler — which can be
implemented in JS.
The interface JS code should implement to receive annotations logged by an
@mozilla.org/cycle-collector-logger;1 instance. Pass an instance of this to
the logger’s ‘processNext’ method.
The methods are a subset of those in nsICycleCollectorListener; see the
descriptions there.