1297048 - [Static Analysis][Dereference before null check] In function DragEvent::InitDragEvent

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Andi [:andi]]

The Static Analysis tool Coverity detected that |mEvent| is dereferenced before being null checked.

>>  MouseEvent::InitMouseEvent(aType, aCanBubble, aCancelable,
>>                             aView, aDetail, aScreenX, aScreenY,
>>                             aClientX, aClientY, aCtrlKey, aAltKey,
>>                             aShiftKey, aMetaKey, aButton, aRelatedTarget);
>>  if (mEventIsInternal && mEvent) {
>>    mEvent->AsDragEvent()->mDataTransfer = aDataTransfer;
>>  }

The dereference takes place in InitMouseEvent:

>>  UIEvent::InitUIEvent(aType, aCanBubble, aCancelable, aView, aDetail);
>>
>>  switch(mEvent->mClass) {
>>    case eMouseEventClass:

In this case this is a false-positive since |mEvent| gets allocated in function Event::ConstructorInit. The call for ConstructorInit is done through the constructor of Event, that finally gets called through contructors of: 
DragEvent->MouseEvent->UIEvent->Event 

What i would like is to remove the null check to eliminate this fp.

Comment 1

[Andi [:andi]]

Attachment: Bug 1297048 - remove useless null check in DragEvent::InitDragEvent.

Review commit: https://reviewboard.mozilla.org/r/73290/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/73290/

Comment 2

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Comment on attachment 8783495 [details]
Bug 1297048 - remove useless null check in DragEvent::InitDragEvent.

https://reviewboard.mozilla.org/r/73290/#review71288

Anyway, mEvent is never nullptr at least in normal path since it's allocated by each constructor when WidgetEvent argument is nullptr.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/750ba0b42ce3
remove useless null check in DragEvent::InitDragEvent. r=masayuki

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/750ba0b42ce3