Re: [Swig-user] Trapping Swig::DirectorException

[Ben W. <be...@sa...>]

On 04/23/2010 01:48 PM, Bob Hood wrote:
> I'm causing a number of Swig::DirectorExceptions to be thrown while
> developing my SWIG wrapper.
...
> I can't seem to find a good "hook" point to trap these.

What we do is use the director:except feature to convert Python 
exceptions in director methods to C++ exceptions. These will then 
terminate the C++ method being called by SWIG; we catch these with 
%exception, and then fail the SWIG wrapper so the original Python 
exception is raised in the Python script. This works reasonably well for us:

%{
   static void handle_exception(void) {
     try {
       throw;
     } catch (std::out_of_range &e) {
       PyErr_SetString(our_index_exception, e.what());
     } etc.
   }
%}

%exception {
   try {
     $action
   } catch (...) {
     # Note that if a director method failed, the Python error indicator
     # already contains full details of the exception, and it will be
     # reraised when we go to SWIG_fail; so no need to convert the C++
     # exception back to a Python one
     if (!PyErr_Occurred()) {
       handle_exception();
     }
     SWIG_fail;
   }
}

%feature("director:except") {
   if ($error != NULL) {
     throw Swig::DirectorMethodException();
   }
}

	Ben
-- 
be...@sa...                      http://salilab.org/~ben/
"It is a capital mistake to theorize before one has data."
	- Sir Arthur Conan Doyle