Question

Possible Duplicate:
Optimization due to constructor initializer list

OK, so here’s my dilemma : Let’s say we’ve got a class, along with several constructors, which are going to be called numerous times (some hundreds of millions of times per second; so speed is crucial).

Which way is preferable? (Is there any difference at all?)

Way A :

// Prototype
class MyClass
{
    public:
        // Constructor
        MyClass (int x, int y, int z) : X(x), Y(y), Z(z) {}

        // Variables
        int X,Y,Z;
};

Way B :

// Prototype
class MyClass
{
    public:
        // Constructor
        MyClass (int x, int y, int z);

        // Variables
        int X,Y,Z;
};

// Implementation
MyClass::MyClass(int x,int y,int z)
{
     this->X=x;
     this->Y=y;
     this->Z=z;
}

Answer 1

You need to use profile tool to measure it by yourself. With build-in types maybe there is no difference (regarding construction speed) but for class types, using a member initializer list is always preferable way.