[Webkit-unassigned] [Bug 14498] New: RenderContainer::positionForCoordinates contains an order of operations error

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=14498

           Summary: RenderContainer::positionForCoordinates contains an
                    order of operations error
           Product: WebKit
           Version: 522+ (nightly)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: aroben at apple.com
                CC: hyatt at apple.com, mitz at webkit.org


Here's the code from RenderContainer::positionForCoordinates (also visible at
http://trac.webkit.org/projects/webkit/browser/trunk/WebCore/rendering/RenderContainer.cpp#L58
):

        int top = borderTop() + paddingTop() + isTableRow() ? 0 :
renderer->xPos();
        int bottom = top + renderer->contentHeight();
        int left = borderLeft() + paddingLeft() + isTableRow() ? 0 :
renderer->yPos();
        int right = left + renderer->contentWidth();

The problem (spotted by prefast) is that the + operator has higher precedence
than the ternary operator, so the code evaluates like this (note the
parentheses):

        int top = (borderTop() + paddingTop() + isTableRow()) ? 0 :
renderer->xPos();
        int bottom = top + renderer->contentHeight();
        int left = (borderLeft() + paddingLeft() + isTableRow()) ? 0 :
renderer->yPos();
        int right = left + renderer->contentWidth();

It's easy to fix (just put parentheses around the ternary expression), but I'm
not sure how to make a test case.


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