bitwise copy constructor

[pacerier]

if i have a class that stores 3 integers, is it true that using the default bitwise copy constructor would be faster then overloading the assignment operator and explicitly transfering the integers over?

[firedraco]

The default copy constructor is NOT bitwise. It calls the copy constructors of every element for you.

[pacerier]

would the default copy constructor be faster then the (explicit) one we would write?

[imi]

It would not be slower.

struct A { int a,b; };
struct B { int a,b; B(const B& x):a(x.a),b(x.b){} };
...
A a1; B b1;
A a2(a1);
B b2(b1);

I wouldn't be surprised if the last two lines yield in exact the same machine code.

However, this may (or may not be) be faster:

struct C { int a,b; }
...
C c1;
C c2; memcpy(&c2, &c1, sizeof(c1));