[xml] Error callbacks when validating using RelaxNG

["Victor Ng" <crankycoder gmail com>]

I'm having some problems trying to figure out how to get the line
number that a document fails at when validating with a RelaxNG schema
definition.

Here is my schema and test data:

Schema :

      1 <?xml version="1.0" encoding="utf-8"?>
      2 <element name="trip" xmlns="http://relaxng.org/ns/structure/1.0">
      3     <element name="description">
      4         <text/>
      5     </element>
      6 </element>

Test document

      1 <?xml version="1.0" encoding="utf-8"?>
      2 <foo/>


Using xmllint - I get a proper line number:

$ xmllint --relaxng rng_schema.xml rng_invalid.xml
<?xml version="1.0" encoding="utf-8"?>
<foo/>
rng_invalid.xml:2: element foo: Relax-NG validity error : Expecting element trip, got foo
rng_invalid.xml fails to validate
$

But when I try to use my own callback function I only seem to get the
message body "Expecting element trip, got foo" without any line numbers.

I'm using a callback function defined as:

     27 void errorFunc (void *ctx, const char *msg, ...)
     28 {
     29     char *tmpChar;
     30     va_list ap;
     31     va_start(ap, tmpChar);
     32     while (tmpChar != 0) {
     33         printf ("[%s]\n", tmpChar);
     34         tmpChar = va_arg(ap, const char *);
     35     }
     36     va_end(ap);
     37 }
     38

The output I get is :
[,I]
[Expecting element trip, got foo
]
[\uffff\uffffs\uffff]

I'm not sure what the garbled data is, but the text seems correct.,

I don't think I'm doing anything weirdly, but my C is extremely rusty.  Anyone have any idea what I'm doing wrong?

Thanks,
-- 
"Never attribute to malice that which can be adequately explained by stupidity."  - Hanlon's Razor