[Webkit-unassigned] [Bug 134632] ASSERTION FAILED: name[0] == '@' && length >= 2 in WebCore::CSSParser::detectAtToken

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=134632


Darin Adler <darin at apple.com> changed:

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--- Comment #2 from Darin Adler <darin at apple.com>  2014-07-04 12:00:13 PST ---
(From update of attachment 234405)
View in context: https://bugs.webkit.org/attachment.cgi?id=234405&action=review

> Source/WebCore/css/CSSParser.cpp:11231
> +            // The standard enables unicode escapes in at-rules. In this case only the resultString will contain the
> +            // correct identifier, hence we have to use it to determine its length instead of the usual pointer arithmetic.

The bug is in parseIdentifier, which needs to bump the result pointer even in the 16-bit slow case. Not doing that will cause many other problems, so just changing this code path to quiet the assertion is wrong. The line of code that should be added to parseIdentifer is:

    result += result16 - start16;

The reason it’s important to fix the bug in parseIdentifier is that multiple call sites of parseIdentifier are affected by this, not just this one code path.

But also, the 16-bit code path in parseIdentifier doesn’t really need to switch to parsing 16-bit input. It’s only the output string that needs to be 16-bit, and the way it currently does things is unnecessarily inefficient. This code is made terribly confusing by using the name "result" for a pointer to the next character to be parsed. We should call this current, not result, and we should also investigate using a const pointer for it and eliminating code that writes into it. But that’s beyond the scope of this.

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