[webkit-dev] Eliminate potential null pointer dereference?

David Barr davidbarr at google.com
Thu Apr 19 22:35:44 PDT 2012

On Fri, Apr 20, 2012 at 3:18 PM, Alexey Proskuryakov <ap at webkit.org> wrote:
> I noticed a number of patches going in recently that add null checks, or refactor the code under the premise of "eliminating potential null dereference". What does that mean, and why are we allowing such patches to be landed?

When there are known conditions for which a value is null that we
would otherwise dereference, check first and take an alternate path in
the null case.

> For example, this change doesn't look nice: <http://trac.webkit.org/changeset/114678/trunk/Source/WebCore/css/CSSStyleSelector.cpp>. We should not try to confuse ourselves with unusual for loop forms, and there is no explanation at all of why these changes are needed. No regression tests either.

Style aside, it is quite clear that the one of the termination
conditions for the first loop is selector == null.
So the second loop ought to check selector != null before any
dereference of selector.

Regarding style, the change homogenizes the loop constructs within that method.

David Barr

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