Natural Docs

I'm trying to use NaturalDocs to document a project and it's not generating
any documentation (it is generating a set of directories and files, just no
documentation).

$ naturaldocs -i iulib -o HTML temp -p temp-proj -r
Finding files and detecting changes...
Parsing 62 files...
Updating menu...
Updating CSS file...
Done.
$ naturaldocs -h | head
Natural Docs, version Development Release 12-07-2007 (1.35 base)
http://www.naturaldocs.org
This program is licensed under the GPL
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Syntax:

NaturalDocs -i [input (source) directory]
(-i [input (source) directory] ...)
-o [output format] [output directory]
$


iulib is a source tree containing standard C++ code with standard C++
extensions (.cc, .h). NaturalDocs should generate reasonable output with
its default settings for such input.