346767 - valgrind warning reading uninitialized memory due to nsBoxFrame::FireDOMEventSynch

Status: RESOLVED FIXED

(Core :: XUL, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

In a Firefox trunk build, when I hover the mouse pointer over the search box in the browser window (not sure which part), I see a valgrind warning, which I'll attached.  I'm pretty sure the cause is this code in nsBoxFrame::FireDOMEventSynch :

      nsEventStatus eventStatusUnused;
      nsEventDispatcher::DispatchDOMEvent(content, nsnull, event,
                                          presContext, &eventStatusUnused);

The fifth parameter to nsEventDispatcher::DispatchDOMEvent is an **optionally null** (I think, although it's not documented!) ****in-out**** (I'm pretty sure of that, but it's also not documented!) parameter.

This seems like a mistake in the tweak in bug 339237 comment 47.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: valgrind warnings

These happen when I move the mouse rightward from the main area of the search box to over the magnifying glass icon.

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: possible patch

This shuts up the warnings, but I'm not sure whether it's really the right thing to do.  Smaug?

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Comment on attachment 231523 [details] [diff] [review]
possible patch

yep, this works. I have to document the nsEventStatus parameter.

Comment 4

[Boris Zbarsky [:bzbarsky]]

And maybe file a followup on documenting this better?

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

Documentation bug is bug 346853.

Comment 6

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Checked in to trunk.