libxml2 error with namespaces and xpath

Turns out, as I found out from here,it is not really a failure of libXml, it's a problem because libXml correctly follows the XML/XPATH specifications.

The solutions proposed by R Bourdeau are correct, however, if you have control of the xml document you are parsing.

The context for the XPATH query is independent of the namespace qualifiers in the xml document. The default namespace forces all child tags into a namespace; they don't require qualification in the document but must be qualified in the xpath query. Fortunately, you registered the namespace as new with libXml, so cateof's solution should work.

xmlXPathRegisterNs(context,  BAD_CAST "new", BAD_CAST "http://www.example.com/new"xmlChar *xpath = (xmlChar*) "/new:book/new:section1";

I'm inlining the xml here for visibility:

<?xml version="1.0" encoding="UTF-8"?><book xmlns="http://www.example.com/new">    <section1>Sec_1</section1>    <section2>Sec_2</section2></book>

This is an annoying failure of the libXml library. As noted by cateof, the problem is the default namespace declaration:

xmlns="http://www.example.com/new"

Two choices:
(1) get rid of that declaration in your book tagor(2) give it a name, and use that name in your tags.

e.g.

xmlns:new="http://www.example.com/new"

Then your tags all look like:

new:booknew:section1

and so on.

it is an issue with the default namespace. To match a path you need /new:tag/new:tagand so on