traceback over C API and PyObject_CallObject

[Gabriel Genellina]

En Fri, 19 Oct 2007 13:53:03 -0300, Sami Vaisanen <ensiferum_ at hotmail.com>  
escribió:

> Hello group,
>
> I'm trying to get the Python exception information (message and  
> traceback)
> stored into a string in my C++ code. However all i get back is the string
> "None".

This is what you get (actually "None\n") when there is no error set.

> All the checks pass and all pointers get a value from the python
> API calls. I've also tried with a different function such as
> PyObject_CallFunctionObjArgs but the result is the same.

Since you already know the three components (type, value, trace), I'd use  
traceback.format_exception instead (and remove the PyErr_Restore call -  
I'm unsure if it works the way you expect it).
In this case you have to pass three arguments, so yes, use  
PyObject_CallFunctionObjArgs (remember the final NULL). Beware:  
format_exception returns a formatted list, not a string. You have to  
concatenate all the elements (either using ''.join or repeteadly calling  
PyString_Concat)

> void get_python_exception(string& message, string& traceback)
> {
>     GIL g;
>    PyObject* type  = NULL;
>     PyObject* value = NULL;
>     PyObject* trace = NULL;
>    PyErr_Fetch(&type, &value, &trace);
>    py_ref ref_type(type);
>     py_ref ref_value(value);
>     py_ref ref_trace(trace);
>    py_ref name(PyString_FromString("traceback"));
>     py_ref module(PyImport_Import(name.get()));
>     if (module)
>     {
>         py_ref fun(PyObject_GetAttrString(module.get(), "format_exc"));
>         if (fun)
>         {
>             PyErr_Restore(type, value, trace);
>             ref_type.release();
>             ref_value.release();
>             ref_trace.release();
>            py_ref ret(PyObject_CallObject(fun.get(), NULL));
>             if (ret && PyString_Check(ret.get()))
>             {
>                 char* str = PyString_AsString(ret.get());
>                 message = str;
>                 traceback = "traceback not available";
>                 return;
>             }
>         }
>     }
>     message   = "message not available";
>     traceback = "traceback not available";
> }




-- 
Gabriel Genellina