I have noticed that cxml is looping for a certain combination of xml/dtd. It loops in the recurse function inside compile-content-model in xml-parse.lisp. I cannot fix it myself but I am hoping that somebody else can find a solution using my minimal reproducible case, which can be found at https://doremir.com/files/cxml/xml-test.zip.

The xml file from the case looks like this:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<!DOCTYPE a PUBLIC "" "">

<a>

  <c/>

</a>

And the dtd file looks like this:

<!ELEMENT b EMPTY>

<!ELEMENT c EMPTY>

<!ELEMENT a ((b?)*, c?)>

The real world case is from MusicXML parsing and the problematic  xml excerpt looks like this:

<sound tempo="90">

  <offset sound="yes">8</offset>

</sound>

And the corresponding dtd excerpt looks like this:

<!ELEMENT sound ((midi-device?, midi-instrument?, play?)*, offset?)>

I have verified this using version "cxml-2008-11-30" from the Closure XML Parser home page at https://common-lisp.net/project/cxml/index.html and also with the latest version from Quicklisp "cxml-20181018".

By the way, why isn't the latest version downloadable from the Closure XML Parser home page?

Thanks!

Sven