Question

Could somebody guide me through what gets called in this scenario?

template<class T>
class mat4 {
public :

T matrix[4][4];

    mat4();
    mat4(vec4<T> i, vec4<T> j, vec4<T> k, vec4<T> t);
    mat4(const T input_matrix[4][4]);

    //~mat4();

    mat4<T> Transposed() const;
    void Transpose();

    mat4<T> Inversed() const;
    void Inverse();

};

With the above code if i call

mat4<float> matrix;
float mf[4][4];

//fill the float matrix here

matrix = mf;

Then i know that the 3rd constructor gets called (it’s not explicit), but what is called beside that? A copy constructor for matrix that takes the temporary object created from the assignment operation? I’m debating whether or not i should create a custom assign operator for it or just let it handle itself. The custom operator would only copy the matrix into the mat4 and return a reference to the mat4, but if there’s no overhead in the automaticly created assignment operator then i’d rather stick to that.

Answer 1

Any decent return value optimization should reduce this to just a call to the third constructor. As long as you’re compiling with optimization, there’s no need to reduce readability to reduce overhead in this case.

Also, I don’t see how a custom copy constructor and/or assignment operator will have less overhead than the compiler-generated ones; they may even complicate the optimization.