Probleme de comprehension : constructeur de copie (templates?)

Bonjour =E0 tous !

Voil=E0 mon petit exemple que je compile en utilisant g++ (cygwin)


#include <iostream>

using namespace std;

template<class T>
class Matrix
{
public:
Matrix(int size);
Matrix(const Matrix<T> &copy);

~Matrix();

Matrix<T>& operator=3D(const Matrix<T>& matrix);

Matrix<T> operator+(const Matrix<T>& second);

private:
int _size;
};

template <class T>
Matrix<T>::Matrix(int size)
: _size(size)
{
cout << "--- Constructor called --- " << endl;
}

template <class T>
Matrix<T>::Matrix(const Matrix<T> &copy)
: _size(copy._size)
{
cout << "--- Copy constructor called --- " << endl;
}

template <class T>
Matrix<T>::~Matrix()
{
cout << "--- Destructor called --- " << endl;
}

template <class T>
Matrix<T>& Matrix<T>::operator=3D(const Matrix<T>& matrix)
{
cout << "--- Operator \"=3D\" called --- " << endl;
_size =3D matrix._size;
}

template <class T>
Matrix<T> Matrix<T>::operator+(const Matrix<T>& second)
{
cout << "--- Operator \"+\" called --- " << endl;
Matrix<T> result(_size);
return result;
}



int main()
{
cout << "Declaration m1" << endl;
Matrix<int> m1(2);
cout << "Declaration m1" << endl;
Matrix<int> m2(2);

cout << "Declaration mSum1" << endl;
Matrix<int> mSum1(2);
cout << "mSum1 =3D m1 + m2" << endl;
mSum1 =3D m1 + m2;

cout << "Declaration mSum2 =3D m1 + m2" << endl;
Matrix<int> mSum2 =3D m1 + m2;

cout << "Declaration mSum3" << endl;
Matrix<int> mSum3(2);
mSum3 =3D m1 + m2;

cout << "Declaration m4 =3D mSum3" << endl;
Matrix<int> m4 =3D mSum3;

int ret;
cin >> ret;

return ret;
}


Comme on voit bien dans le programme en bas la cr=E9ation est appell=E9e
plusieurs fois.

Et voil=E0 la sortie du programme :

$ ./a.exe
Declaration m1
--- Constructor called ---
Declaration m1
--- Constructor called ---
Declaration mSum1
--- Constructor called ---
mSum1 =3D m1 + m2
--- Operator "+" called ---
--- Constructor called ---
--- Operator "=3D" called ---
--- Destructor called ---
Declaration mSum2 =3D m1 + m2
--- Operator "+" called ---
--- Constructor called ---
Declaration mSum3
--- Constructor called ---
--- Operator "+" called ---
--- Constructor called ---
--- Operator "=3D" called ---
--- Destructor called ---
Declaration m4 =3D mSum3
--- Copy constructor called ---
0
--- Destructor called ---
--- Destructor called ---
--- Destructor called ---
--- Destructor called ---
--- Destructor called ---
--- Destructor called ---


Ce que m'int=E9resse le plus c'est pourquoi j'ai ces lignes l=E0 :
Declaration mSum2 =3D m1 + m2
--- Operator "+" called ---
--- Constructor called ---

Je ne vois pas l'operator=3D ni de constructeur de copie. Si je mets le
vrai code pour la classe matrix, le mSum2 est en effet la somme des 2,
l'objet est cr=E9=E9 et vit bien =E7a vie...

Quelqu'un saurait-il m'expliquer la suite des appels ici ? J'imagine
que la ligne
--- Constructor called ---
correspond =E0 la cr=E9ation de l'objet temporaire dans l'operator +. Mais
o=F9 est la trace de l'operator =3D ?



Merci d'avance
A+