875895 - assertion with WantAllTraces

Status: RESOLVED INVALID

(Core :: XPCOM, defect)

Description

[Andrew McCreight [:mccr8]]

Benoit is hitting this assertion I added in bug 873111:
1867        MOZ_ASSERT(nsCycleCollectionNoteRootCallback::WantAllTraces() ==
1868                   nsCycleCollectionTraversalCallback::WantAllTraces());

I'm going to guess that I just totally botched this and never tested WantAllTraces().

Comment 1

[Andrew McCreight [:mccr8]]

Much to my surprise, I didn't totally mess this up, and it seems okay to me in a local OSX build with the basic AllTraces() instructions from 
  https://wiki.mozilla.org/Performance:Leak_Tools#Cycle_collector_heap_dump

What did you do to trigger this assertion, Benoit?

Comment 2

[Benoit Jacob [:bjacob] (mostly away)]

So all I did was use a built with my 'refgraph' patch and do a regular cycle collection,

    window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
        .getInterface(Components.interfaces.nsIDOMWindowUtils)
        .cycleCollect();

However I just realized now that I still have this hunk in my patch,

--- a/xpcom/glue/nsCycleCollectionTraversalCallback.h
+++ b/xpcom/glue/nsCycleCollectionTraversalCallback.h
@@ -46,7 +46,7 @@ public:
   };
   uint32_t Flags() const { return mFlags; }
   bool WantDebugInfo() const { return (mFlags & WANT_DEBUG_INFO) != 0; }
-  bool WantAllTraces() const { return (mFlags & WANT_ALL_TRACES) != 0; }
+  bool WantAllTraces() const { return true; }
 protected:
   nsCycleCollectionTraversalCallback() : mFlags(0) {}
 

Do I still need this, however? I am now using a custom subclass of nsICycleCollectorListener where GetWantAllTraces gives true.

Trying without the above hunk, but I would like a confirmation that just having the listener's GetWantAllTraces give true is enough to ensure that a CycleCollectNow call on this listener will do AllTraces.

Comment 3

[Andrew McCreight [:mccr8]]

Oh, yeah, that would be the problem. :)  In the future if you want to do that for some reason, you'll have to make a similar change to nsCycleCollectionNoteRootCallback::WantAllTraces().

Making GetWantAllTraces() on the listener returning true should be enough.

Thanks for the followup.

Comment 4

[Benoit Jacob [:bjacob] (mostly away)]

Sorry about the noise and thanks for the great customer support!