默认的Copy构造函数和默认的赋值运算符

Question

what is the difference between either of these used in a code as i have used here .(line 44 ad line 45 both work fine)

Excerpt:

Date temp = *this;  //ASSIGNMENT OPERATOR CALL(PROVIDED BY COMPILER)
//Date temp(*this); //COPY CONSTRUCTOR CALL(PROVIDED BY COMPILER)

My Opinion : Is it that during assignment like object1 = object2; contents of object2 are deleted and placed in object1 while while if the same thing happens via a copy constructor contents of object2 still remain( i mean just as the word suggests "copy").

NOTE: By the way my code compiled fine in Microsoft visual C++ 2008 but it gave a warning

  prog.cpp: In function ‘std::ostream& operator<<(std::ostream&, const Date&)’:
  prog.cpp:103: warning: deprecated conversion from string constant to 

in ideone.com.Any reasons for that.

Answer 1

Date temp = *this; 
Date temp(*this); 

Both call copy constructor,
First is called as Copy Initialization & second is called as Direct Initialization .

Simple Rule to remember this is:
If an object is getting created as well as initialized in the same statement then it calls Copy constructor.

If an object is just assigned and not being created in the same statement then it calls Assignment(Copy Assignment) operator.

---

The compiler complains because:

An ordinary string literal has type “array of n const char”. And implicit conversion from const to non-const qualification for string literals (4.2) is deprecated.

References:
C++ Standard Section [2.13.4/2]:
An ordinary string literal has type array of n const char , where n is the size of the string as defined below; it has static storage duration (3.7) and is initialized with the given characters.

Annexure D section [D.4/1]
The implicit conversion from const to non-const qualification for string literals (4.2) is deprecated.

So to avoid the warning You should use:

static const char *monthName[13]
      ^^^^^^^ 

Answer 2

static char *monthName[13]

can/should be

static const char *monthName[13]

to avoid the warning.

Answer 3

The difference between the default copy constructor and the default assignment operator is that when the assignment operator is called, the members of the receiving object are already initialized with values, and you are simply replacing them with copies of the values in the second object. With the copy constructor, the members are initialized as copies of the members in the second object. The second object should be completely unaffected by either operation.

However, you are not using the assignment operator in your code, you are using the copy constructor. If you had done this:

Date temp;
temp = *this;

Then you would be using the assignment operator.