Bug 80224 – DocumentOrderedMap::containsMultiple can incorrectly return true after an item is removed

• Status: RESOLVED
• Resolution: FIXED
• Component: DOM

[Darin Adler]

There are two related design problems in DocumentOrderedMap.

A

There is a bug: DocumentOrderedMap::containsMultiple will return an incorrect result in the following case:

1) There are two elements in the map.
2) The first element is removed.
3) containsMultiple will return true, but it should return false.

This bug can’t be fixed because containsMultiple does not know which key match function to use.

B

If a caller uses the wrong “get” function on the DocumentOrderedMap, then the map will have incorrect contents. The key matching function is implicit in which of the three get functions is called.

It’s not immediately obvious how to solve these problems. One way to fix problem A is to make three different containsMultiple functions for each of the three different key types. One way to fix both problems is to make DocumentOrderedMap be a class template and make the type of key (id, map name, lowercased map name) be a template argument. There might be even better solutions.

[Darin Adler]

It looks like these problems date back to when I first created the class and were not introduced when moving it to a separate file.

[Darin Adler]

But the fact that the key matching functions are “baked into the class” are part of moving this to a separate file, and those did make problem B worse.

[Darin Adler]

A is not really a design problem!

The question can be correctly answered with a different implementation.

[Darin Adler]

I am going to repurpose this to just deal with the correctness problem.

[Dimitri Glazkov (Google)]

(In reply to comment #4)
> I am going to repurpose this to just deal with the correctness problem.

I love it when you get back into coding.

[Darin Adler]

(In reply to comment #5)
> I love it when you get back into coding.

I only wish I had more time for it.

[Ryosuke Niwa]

(In reply to comment #0)
> There are two related design problems in DocumentOrderedMap.
>
> There is a bug: DocumentOrderedMap::containsMultiple will return an incorrect result in the following case:
> 
> 1) There are two elements in the map.
> 2) The first element is removed.
> 3) containsMultiple will return true, but it should return false.

I'm certain http://trac.webkit.org/changeset/149652/trunk/Source/WebCore/dom/DocumentOrderedMap.h addressed this issue.