I've been working on a project that ties together a few different systems and technologies, and the whole thing is written in C++ and uses a lot of MFC and Windows libraries (don't ask, it's a long story).  I was working on integrating a third-party application that produces XML documents that are parsed by the application under development when I hit a weird snag.  The third-party application would produce an schema file with a namespace declaration like this:

xmlns:xml="http:www.w3.org/XML/1998/namespace"

Note that this is technically legal.  The namespace prefix "xml" is reserved, but if defined, it must point to the W3C namespace schema definition.  Technically, it is implied so it is not present in most documents, but making the legal, yet redundant, declaration is not technically wrong.  However, the older Microsoft XML library I have been working with (i.e. MSXML which is pre-.NET) complains about it saying "the namespace prefix 'xml' is reserved and may not be declared".  It's not checking if it has been declared correctly. 

So I'm stuck between two pieces of code I don't control: one that is doing something that is technically legal but unnecessary, and the other that is performing an error check that is sort of correct, but not really.  So where is the bug?  It's a little bit on both sides, or what I call a "bug in the cracks": something that emerges from the interaction of two pieces that are doing something fairly reasonable, but in an incompatible way.  My workaround is somewhat unfortunate. I have to do a string-level manipulation of the XML document before it gets passed to the MSXML parser to strip out the offending namespace declaration, since I can't actually parse it to fix it.  Hopefully we'll soon be able to upgrade to a newer version of the XML libraries (or maybe even move the whole thing to C#/.NET) and then this problem and the associated workaround will simply vanish.