Copying constructor and calling of default constructor

C ++ primer version 4, 619th:

Panda ying_yang ("ying_yang"); // create a panda object

Panda ling_ling = ying_yang // uses copy constructor

At first, I was surprised to call the copy constructor In the second statement. I felt that the value assignment operator function should be called. Otherwise, see the followingCode:

Code

# Include < Iostream >
Using   Namespace STD;

Class   Base {
Public :
Base (): I ( 0 )
{
Cout <   " Default Construction "   < Endl;
}
Base ( Const   Base & RHS): I (RHS. I)
{
Cout <   " Copy Construction "   < Endl;
}

Operator = ( Const   Base & RHS)
{
I = RHS. I;
Cout <   " Copy Operator "   < Endl;
}

Private:
IntI;
};

IntMain ()
{
BaseB;
BaseB1=B;
BaseB2;
B2=B;
}

 

Running result:

 

Note: panda ling_ling = ying_yang; refers to the replication constructor, because the ling_ling object is not created, initialized, and cannot be assigned a value, therefore, you must execute the copy constructor to create an object.

 

In addition, once a class defines a constructor, the compiler will not synthesize the default constructor for it.