Impossible to chain the SAX warning/error handlers to the default implementation
Normally with the SAX handlers, it's possible to override the default handler with a custom handler, which can then potentially call back to the default implementation.
But this is not possible for the warning/error handlers, as by default they use xmlParserError / xmlParserWarning, which take variadic arguments, but where there is no variant that takes a va_list
.
It would be nice to add variants of xmlParserError / xmlParserWarning that take variadic lists, similar to vprintf.