Closed Bug 1187055 Opened 8 years ago Closed 8 years ago

crash in mozilla::a11y::ProxyDestroyed(mozilla::a11y::ProxyAccessible*)


(Core :: Disability Access APIs, defect)

42 Branch
Windows NT
Not set



Tracking Status
firefox42 --- fixed


(Reporter: away, Assigned: tbsaunde)



(Keywords: crash, Whiteboard: [Nightly top crasher])

Crash Data


(1 file)

This bug was filed from the Socorro interface and is 
report bp-ec4bb98f-29a2-4481-9a98-d03ed2150722.

This spiked in nightly 20150721030212 and is 25% of current crashes on that channel.

Frame 	Module 	Signature 	Source
0 	xul.dll 	mozilla::a11y::ProxyDestroyed(mozilla::a11y::ProxyAccessible*) 	accessible/windows/msaa/Platform.cpp
1 	xul.dll 	mozilla::a11y::DocAccessibleParent::Destroy() 	accessible/ipc/DocAccessibleParent.cpp
2 	xul.dll 	mozilla::a11y::DocAccessibleParent::RecvShutdown() 	accessible/ipc/DocAccessibleParent.cpp
3 	xul.dll 	mozilla::a11y::PDocAccessibleParent::OnMessageReceived(IPC::Message const&) 	obj-firefox/ipc/ipdl/PDocAccessibleParent.cpp
4 	xul.dll 	mozilla::dom::PContentParent::OnMessageReceived(IPC::Message const&) 	obj-firefox/ipc/ipdl/PContentParent.cpp
5 	xul.dll 	mozilla::ipc::MessageChannel::DispatchAsyncMessage(IPC::Message const&) 	ipc/glue/MessageChannel.cpp
6 	xul.dll 	mozilla::ipc::MessageChannel::DispatchMessageW(IPC::Message const&) 	ipc/glue/MessageChannel.cpp
7 	xul.dll 	mozilla::ipc::MessageChannel::OnMaybeDequeueOne() 	ipc/glue/MessageChannel.cpp
8 	xul.dll 	MessageLoop::DoWork() 	ipc/chromium/src/base/
|wrapper| is null at ProxyDestroyed. Is this a simple null-check or is there some deeper invariant being broken here?
Flags: needinfo?(tbsaunde+mozbugs)
(In reply to David Major [:dmajor] from comment #1)
> |wrapper| is null at ProxyDestroyed. Is this a simple null-check or is there
> some deeper invariant being broken here?

That function should be called whenever a proxy is destroyed, and called only once for a given proxy.  ProxyCreated always sets proxy->mWrapper to point at an object.  So that seems wrong, but I'm not sure we can really debug it, so I'd take / write a patch adding a null check.
Flags: needinfo?(tbsaunde+mozbugs)
(In reply to Guilherme Lima from comment #3)
> When Nightly crashes now it produces two entries on about:crashes?

That sounds wrong, we shouldn't do that. We should see to get one crash report with multiple dumps attached.
Unless there's some bug in the code that causes simultaneous (but not directly-tied-together) crashes in both the parent and content processes.
One of the comments: "The site looks like a sure way to make it happen."
Whiteboard: [Nightly top crasher]
Trevor can you or Lorien write the patch (or debug)?
Assignee: nobody → tbsaunde+mozbugs
All proxies should have wrappers on windows.  So it doesn't make much sense
that we need a null check here, however it seems to happen in the wild that
proxy->GetWrapper() returns null.
Attachment #8639543 - Flags: review?(dbolter)
Attachment #8639543 - Flags: review?(dbolter) → review+
Closed: 8 years ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla42
Crash stats seems to agree this is fixed. :)
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