XML to SXML is probably works
(This post was written yesterday, but due to internet outage I'm posting it only now.) Exactly as I expected, implementation of conversion of attributes and namespace definitions has taken one working block. The second milestone is now near.
Work can't be considered finished unless automatic tests are written. Now I'm thiking how I can reuse the tests of SXML to XML conversion.
I'm also going to add some new tests. At least, I'd like to test all combinations of "has attributes or not" and "has namespace definitions or not".
Another (I hope small) issue is that I've got the warning "lookup_or_mk_ns: xmlNewNs failed" followed by "scm_to_node: namespace declaration for '' is not complete". I expect it's not a bug but a feature, but anyway should check for the reason.
By the way, while programming, at some moment I started to get coredumps. After some investigation I found that the problem is due to "xmlStrcat". This function reallocates its first parameter, but documentation doesn't say about it. I'm going to submit a bug.