Since the C standard library does not have a library for this, what should I use?
Note: This is intended to be a definitive, C -FAQ-style question for this. I did not simply appropriate those other questions because they tended to ask for something slightly more specific. Just like with standard library containers, what library you should use depends on your needs.
There is another approach to handling XML that you may want to consider, called XML data binding.
Especially if you already have a formal specification of your XML vocabulary, for example, in XML Schema.
You have chosen: Rapid XML This XML parser is exactly what it says on the tin: rapid XML. But maybe you need something a bit less bare-bones.