Show how to handle a custom exception class in the example

Define "throws" typemap for it.

Examples/c/exception/example.i

@@ -5,6 +5,10 @@
 #include "example.h"
 %}
 
+%typemap(throws, noblock="1") Exc {
+  SWIG_exception(SWIG_RuntimeError, $1.msg);
+}
+
 /* Let's just grab the original header file here */
 %include "example.h"