477326 - valgrind: uninitialized nsXULPopupManager::mCachedMousePoint running test_closemenu_attribute.xul

Status: RESOLVED FIXED

(Core :: XUL, defect)

Description

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

Attachment: valgrind warnings

When I run the mochitest toolkit/content/tests/widgets/test_closemenu_attribute.xul under valgrind on Linux, I see a series of warnings about conditional jumps depending on uninitialized values.  Note that the stacks for these warnings can be a decent distance away from the cause of the problem, since valgrind only warns when uninitialized data is used for a branch or a system call.

The first of the warnings is probably the first to look into, but the best technique is often to force other (earlier) branches based on the pieces of data that might be suspicious, and see which ones valgrind warns about.  (e.g., if ... == nsnull ) { printf("hi") })

Comment 1

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

My initial suspicion about where the uninitialized data came from turned out to be correct (based on adding a printf of the data itself, actually).  The problem here is that in nsXULPopupManager::FirePopupShowingEvent, mCachedMousePoint is uninitialized.

Comment 2

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

(In reply to comment #1)
> mCachedMousePoint is uninitialized.

I should say, is uninitialized or was initialized from something that was in turn uninitialized (etc., ad. inf.).

Comment 3

[Neil Deakin]

Attachment: nsPoints don't initialize in their default constructor so assign directly