A simple example of C++ Exceptions

Exceptions is a very powerful mechanism by which errors can be handled within the programs in C++. In C if an exception occurs (for example overflow, underflow, memory allocation failure, etc) then the program would just crash. In C++ these problems can be handled by use of exceptions.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//This example shows different ways of throwing and catching 
//exceptions and handling of exceptions

#include<iostream>
//#include<exception> //May be required on other platforms

using namespace std;

void function1();
void function2();
void function3();
void function4();

class zgException: public exception
{
  //overloading the what() method
  virtual const char* what() const throw()
  {
    return "zgException occured";
  }
} zgEx;


int main()
{
  function1();
  function2();
  function3();
  function4();

  return 0;
}

//Throwing an integer
void function1()
{
  cout<<"\nfunction1()"<<endl;
  try
  {
    throw 123;
  }
  catch(int a)
  {
    cout<<"Exception caught with value "<<a<<endl;
  }
}

//Throwing a string but no mechanism to catch it
void function2()
{
  cout<<"\nfunction2()"<<endl;
  string s = "function2() exception";
  try
  {
    throw s;
  }
  catch(exception &e)
  {
    cout<<"Exception message: "<<e.what()<<endl;
  }
  catch(...)
  {
    cout<<"All exceptions not handled are caught here"<<endl;
  }
}

//Throwing a string and catching it
void function3()
{
  cout<<"\nfunction3()"<<endl;
  string s = "function3() exception";
  try
  {
    throw s;
  }
  catch(exception &e)
  {
    cout<<"Exception message: "<<e.what()<<endl;
  }
  catch (string &ss)
  {
    cout<<"Exception message: "<<ss.c_str()<<endl;
  }
  catch(...)
  {
    cout<<"All exceptions not handled are caught here"<<endl;
  }
}

//Throwing a class and catching it
void function4()
{
  cout<<"\nfunction4()"<<endl;
  string s = "function4() exception";
  try
  {
    throw zgEx;
  }
  catch(exception &e)
  {
    cout<<"Exception message: "<<e.what()<<endl;
  }
  catch(...)
  {
    cout<<"All exceptions not handled are caught here"<<endl;
  }
}

The output is as follows: