counting constructor calls
I counted 1 default ctor, 2 copy ctor and 1 assignment calls for the following statements and I am wondering for what 2 copy ctor calls are necessary?
T t503; t503 = g<T>(t3);
Where T and g are given by
class T{public: int i;T(int i):i(i){};/*some more member funcs helping counting*/};
template <class Type>
const Type g(Type t){return t;}
and t3 is given by T t3(3);
T t503; t503 = g<T>(t3);
Where T and g are given by
class T{public: int i;T(int i):i(i){};/*some more member funcs helping counting*/};
template <class Type>
const Type g(Type t){return t;}
and t3 is given by T t3(3);
The default construct happens when you do
Another constructor is called when you do
The first copy constructor is called when you pass t3 as a parameter to the g() function. Since you are passing by value, you are actually passing a copy of the object.
The second copy constructor is called when you return t from the g() function.
The assignment operator call is obvious.
Note that in an optimized build, it's very likely that both copy constructors can be optimized away resulting in 0 copy ctor calls. But it depends on the circumstances.
T t503;Another constructor is called when you do
T t3(3); -- but this is not a default or copy construct.The first copy constructor is called when you pass t3 as a parameter to the g() function. Since you are passing by value, you are actually passing a copy of the object.
The second copy constructor is called when you return t from the g() function.
The assignment operator call is obvious.
Note that in an optimized build, it's very likely that both copy constructors can be optimized away resulting in 0 copy ctor calls. But it depends on the circumstances.
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