Re: Exception Destructor on new

From:

"Jim Langston" <tazmaster@rocketmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 23 Mar 2007 09:05:11 -0700

Message-ID:

<0VSMh.12$yk3.7@newsfe06.lga>

"Subra" <mailursubbu@gmail.com> wrote in message
news:1174620240.892541.120780@n76g2000hsh.googlegroups.com...

Hi,

I am learning C++ and need export advice on the below program.
I have read it that whenever a exception is genrated and control
enteres the catch block it will call destructors for all the
successfuly completed constructors. But in the below case
i am doing :-
       base *ptr=new base;
       throw 44;
But the destructor for base is not called once it enters the catch
block. Please let me know why it is so and how to come out of it.

#include<iostream>
#include<exception>
using namespace std;
class base
{
   public:
       base() { cout<<"Constructor"<<endl; }
       ~base() { cout<<"Destructor"<<endl; }
};
int main()
{
   try {
       base *ptr=new base;

You are constructing a base pointer. With new it calls a base constructor.

throw 44;

Even without this throw, the destructor for base isn't going to be called,
because you never did delete ptr.

   }catch(...) { // I am
expecting base destructor to be called here
       cout<<" Inside catch"<<endl; // But it is not
   }

The base pointer is destroyed. But, if you call new, you have to call
delete. Which you haven't.

Objects instantized with new never have their destructors called unless you
call delete (there may be exceptions, but this is the general rule). If you
want your base instance destructor called (and you do) then you have to call
delete ptr.

}