Bug 39280 – Wrong ternary in CSSStyleSelector::SelectorChecker::checkOneSelector

• Status: RESOLVED
• Resolution: WONTFIX
• Component: CSS

[Yoshiki Hayashi]

In CSSStyleSelector::SelectorChecker::checkOneSelector and checkSelector in WebCore/css/CSSStyleSelector.cpp, there are multiple occurrence of ternary that looks like:
RenderStyle* parentStyle = elementStyle ? elementParentStyle : e->parentNode()->renderStyle();
where it should look like:
RenderStyle* parentStyle = elementParentStyle ? elementParentStyle : e->parentNode()->renderStyle();

If I'm reading the code correctly, elementStyle and elementParentStyle are either both NULL or both non-NULL so there isn't any visible problem because of this code.  However, I think it's worth fixing so I'm going to attach a patch to fix it.

Thanks,

[Yoshiki Hayashi]

Created attachment 56353 [details]
Proposed Patch

Actually, I think this was done on purpose. I would add an assertion that elementParentstyle is null iff elementstyle is null, but not change this code, as it is slightly more robust.

[Darin Adler]

Comment on attachment 56353 [details]
Proposed Patch

You couldn't find any case where this led to a null-dereference? If you could find a case then it would be best to add a test case to demonstrate the problem.

r=me

Comment on attachment 56353 [details]
Proposed Patch

I am sorry. I should have set to r- based on my comment. Please don’t make this change.

(In reply to comment #3)
> (From update of attachment 56353 [details])
> You couldn't find any case where this led to a null-dereference?

parentStyle appears to be null-checked everywhere.

[Yoshiki Hayashi]

Thank you Dan and Darin for prompt review.  Since the code is intentional according to Dan, I'm just going to close this issue.

Thanks,