From: "Richard P. Groenewegen" <rpg@...2all.net>
Date: 2004-10-26T05:07:55+09:00
Subject: Re: "add" function in swig and the ruby GC?

> Try to post the smallest complete interface file and script that
> demonstrates the problem, and then the answer may be more obvious.

Thanks for the reply and the comment about auto_ptr.  I'll be using
that.  As for the smallest complete example:

//-------------------------------------------------------------------
// thingy.h
//-------------------------------------------------------------------
    #include <iostream>
    using namespace std;
    class Thingy {
        public:
            Thingy() {
                _number = ++number;
                cout << "Thingy " << _number << " constructed.\n";
            }
            ~Thingy() {
                cout << "Thingy " << _number << " destructed.\n";
            }
            Thingy * add(Thingy *other) {
                return new Thingy();
            }
            static int number;
        protected:
            int _number;
    };

//-------------------------------------------------------------------
// thingy.cxx
//-------------------------------------------------------------------
    #include "thingy.h"
    int Thingy::number = 0;

//-------------------------------------------------------------------
// thingy.i
//-------------------------------------------------------------------
    %module thingy

    %{
    #include "thingy.h"
    %}

    %include "thingy.h"

//-------------------------------------------------------------------
// irb output (slightly trimmed):
//-------------------------------------------------------------------
    irb> require 'thingy.so'
    irb> a = Thingy::Thingy.new
    Thingy 1 constructed.

    irb> b = Thingy::Thingy.new
    Thingy 2 constructed.

    irb> c = a.add(b)
    Thingy 3 constructed.

    irb(main):005:0> a,b,c, = 0,0,0

    irb(main):006:0> GC.start
    Thingy 2 destructed.
    Thingy 1 destructed.
    
As you can see.  Thingy 3 does not get destructed.  I tried changing
the function add to

    void add(Thingy *other, Thingy *OUTPUT) {
        OUTPUT = new Thingy();
    }

and include "typemaps.i" in the thingy.i file as (sort of) is
suggested in the swig documentation but that does not work.


best regards,
Richard