Exception Handling and Object Destruction

Exception Handling On Destructors

We will learn this concept with the help of an example given below:

Example Code:

#include <iostream> 
using namespace std; 
  
class Test { 
public: 
//Constructor
  Test() { cout << "Constructing an object of Test class" << endl; } 
//Destructor
  ~Test() { cout << "Destructing an object of Test class " << endl; } 
}; 
  
int main() { 
  try { 
    Test t1; 
//Throw passes an argument ot the exception handler. 
//Here int 10 is passed as an argument.
    throw 10; 
  } catch(int i) { 
    cout << "Caught " << i << endl; 
  } 
} 

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Output

Constructing an object of Test class
Destructing an object of Test class 
Caught 10

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Explanation: 

When an exception is thrown, the objects' destructors (whose scope ends with the try block) are automatically triggered before the catch block is performed. As a result, the preceding software outputs "Destructing an item of Test" before "Caught 10."

Exception inside Constructors

We will understand this concept with the help of the following example:

Example Code:

#include <iostream> 
using namespace std; 
  
class Test1 { 
public: 
  Test1() { cout << "Constructing an Object of Test1" << endl; } 
  ~Test1() { cout << "Destructing an Object of Test1" << endl; } 
}; 
  
class Test2 { 
public: 
  // Following constructor throws an integer exception 
  Test2() { cout << "Constructing an Object of Test2" << endl;  
            throw 20; } 
  ~Test2() { cout << "Destructing an Object of Test2" << endl; } 
}; 
  
int main() { 
  try { 
    Test1 t1; // Constructed and destructed 
    Test2 t2; // Partially constructed 
    Test1 t3; // t3 is not constructed as this statement never gets executed 
  } catch(int i) { 
    cout << "Caught " << i << endl; 
  } 
} 

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Output:

Constructing an Object of Test1
Constructing an Object of Test2
Destructing an Object of Test1
Caught 20

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Explanation:

Destructors are only invoked for properly developed constructed objects. When a function object throws an exception, the object's destructor is not invoked.

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Must Read Dynamic Binding in C++

Frequently Asked Questions

What is the purpose of using a destructor in C++?

The primary function of the destructor is to release any resources (opened files, opened sockets, database connections, resource locks, and so on) allocated throughout the lifetime of your object.

Does the C++ compiler create a default constructor when we write our own?

In C++, the compiler builds a default constructor for each class by default. However, the compiler will not generate the default constructor if we specify our constructor.

What is the order of constructor execution in C++?

The base class constructor is run first, followed by the derived class constructor. Thus execution proceeds from top to bottom in the inheritance tree.

Conclusion

In this article, we have extensively discussed exceptional handling and object destruction in C++ with the help of various examples. We have also brushed up on some of the important C++ topics like C++ constructors, destructors, exceptions etc.  We hope this blog has helped you enhance your knowledge regarding the C++ concepts. Some official documentation on big data that can help you improve your understanding is this Pointer in C++ and Local class.

If you would like to learn more, check out our articles on Operator Keyword in C#, cloud platform comparison, and 10 AWS best books.  Practice makes a man perfect. To practice and improve yourself in the interview, you can check out Top 100 SQL problems, Interview experience, Coding interview questions, and the Ultimate guide path for interviews.

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