[Swig-user] Saving Python reference to string argument

[Raoul G. <rao...@ya...>]

I have a low-level C++ tracing class that I'm trying to wrap for
Python, which has an interface like this:

struct TraceObject {
  TraceObject(char const *functionName);
  // ...
private:
  char const *m_functionName;
};

The problem is that it assumes the string passed to the constructor has
static storage duration, e.g.

void foo() {
  TraceObject e("foo");  // OK - "foo" string lives forever

  // ...
}

However, when I construct one of these from Python, it gets passed a
Python string which nobody saves a reference to. The string then gets
destroyed, leaving a dangling pointer in the C++ object:

e.g.
>>> e = TraceObject("foo")   # PROBLEM

I guess what I would like is for the Python wrapper object to save a
reference to the string argument passed to its __init__ function.
Something along the lines of this:

class TraceObject(_object):
    def __init__(self, *args):
        _swig_setattr(self, TraceObject, 'this',
_TraceObject.new_TraceObject(*args))
        _swig_setattr(self, TraceObject, 'thisown', 1)
        self.saved_arguments = args

That way the Python shadow class will save a reference to the Python
string until it gets deleted itself. I don't see how to get swig to
generate this kind of code, though. Can anyone suggest how to deal with
this?

-- 
Raoul Gough.


	
	
		
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