Re: Exception Handling constructor

From:

=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 13 Jan 2008 11:37:55 GMT

Message-ID:

<nKmij.2700$R_4.1930@newsb.telia.net>

On 2008-01-13 10:32, Sunil Varma wrote:

Hi,

   Here is a piece of code where the constructor throws an exception.

class A
{
    int n;
    public:
        A()
        try{
            {
                throw 10;
            }
        }
        catch(const int &e)
        {
            cerr<<""<<endl;
        }
        A(const int &i)
        try{
            {
                if(i == 0)
                    throw 10;
                n = i;
            }
        }
        catch(const int &e)
        {
            cerr<<"Exception raised in parameterised constructor"<<endl;
        }
        int get_value()
        {
            return n;
        }
};

void main()
{
    A obj(10);
    cout<<obj.get_value()<<endl;
    A obj1(0);
}

When execute the above code I got the following output on g++
compiler.

10
Exception raised in parameterised constructor
terminate called after throwing an instance of 'i'

What is the logical state of an object if the constructor throws an
exception, here the object obj1.

When the end of a function try block handler in a constructor is reached
the exception is rethrown (which is why terminate() is called), so the
effects should be the same as throwing an exception in a normal
constructor, i.e. there is no object obj1.

And in case if the constructor has a parameter initialization list,
how should the try{} catch(){} be.

struct Foo
{
  int nr;
  Foo(int n)
  try
    : nr(n)
  {
    // So some more construction
  }
  catch(std::exception& e)
  {
    // Handle exception
  }
};

Notice that the initialisation list comes between the 'try' and the '{'.
If an exception is thrown either in the initialisation list of the body
of the try-block control will be transferred to the appropriate catch-
block.

--
Erik Wikstr?m