Chapter 14: Problem 7

When is a copy constructor called?

Short Answer

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In C++ programming language, a copy constructor is called in several situations, including: 1. Initialization with another object during declaration: When a new object is initialized with an existing object during its declaration, the copy constructor is called. 2. Passing an object as an argument to a function: When an object is passed as an argument to a function, the copy constructor is involved. 3. Returning an object from a function: The copy constructor is called when an object is returned from a function. 4. Using the copy assignment operator: Although not directly calling the copy constructor, using the copy assignment operator can indirectly involve a copy constructor when creating a temporary object (compiler dependent).

Step by step solution

1. Initialization with another object during declaration

A copy constructor is called when a new object is initialized with an existing object during its declaration. Example: ``` class MyClass { public: int data; // Copy Constructor MyClass(const MyClass &source) { data = source.data; } }; int main() { MyClass obj1; obj1.data = 10; // Copy constructor is called here MyClass obj2(obj1); return 0; } ``` In the above example, `obj2` is initialized using `obj1` and thus, the copy constructor is called.

2. Passing an object as an argument to a function

A copy constructor is called when an object is passed as an argument to a function. Example: ``` void Func(MyClass obj) { } int main() { MyClass obj; obj.data = 10; // Copy constructor is called here Func(obj); return 0; } ``` In the above example, the copy constructor is called when `obj` is passed to the function `Func()`.

3. Returning an object from a function

A copy constructor is called when an object is returned from a function. Example: ``` MyClass Func() { MyClass obj; obj.data = 10; return obj; } int main() { // Copy constructor is called here MyClass newObj = Func(); return 0; } ``` In this example, the copy constructor is called when the object `obj` is returned from the `Func()` function and assigned to `newObj`.

4. Using the copy assignment operator

Although not directly calling the copy constructor, using the copy assignment operator can indirectly involve a copy constructor when creating a temporary object. Example: ``` MyClass obj1; obj1.data = 10; // Copy constructor might be called here (compiler dependent) MyClass obj2 = obj1; ``` In the above example, the assignment `obj2 = obj1` might call the copy constructor to create a temporary object, which will then be assigned to `obj2` using the copy assignment operator. However, this behavior depends on the compiler and optimizations.

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When is a copy constructor called?

Short Answer

Step by step solution

1. Initialization with another object during declaration

2. Passing an object as an argument to a function

3. Returning an object from a function

4. Using the copy assignment operator

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