JS_TracerInit
in the latter case, the only operations the callback may perform on thing are to call js_tracechildren or the debug-only js_printtracethinginfo function.
... description js_tracechildren and other tracing apis call the tracer callback for each traceable thing directly referenced by a particular object or runtime structure.
... it is the callback's responsibility to ensure the traversal of the full object graph, if desired, by eventually calling js_tracechildren on the passed thing.

Index
491 js_tracerinit jsapi reference, obsolete, spidermonkey js_tracechildren and other tracing apis call the tracer callback for each traceable thing directly referenced by a particular object or runtime structure.
... it is the callback's responsibility to ensure the traversal of the full object graph, if desired, by eventually calling js_tracechildren on the passed thing.

JSAPI reference
(for example, these apis support very smooth integration between the js garbage collector and other garbage collectors.) struct jstracer added in spidermonkey 1.8 js_tracechildren added in spidermonkey 1.8 js_traceruntime added in spidermonkey 1.8 jsval_is_traceable added in spidermonkey 1.8 obsolete since jsapi 31 jsval_to_traceable added in spidermonkey 1.8 obsolete since jsapi 31 jsval_trace_kind added in spidermonkey 1.8 obsolete since jsapi 31 js_tracer_init added in spidermonkey 1.8 obsolete since jsapi 12 js_tracerinit added in spidermonkey 12 obsolete sinc...