C++: destructor and delete

[Newsnet Customer]

Hi,

Statement 1: "A dynamically created local object will call it's destructor
method when it goes out of scope when a procedure returms"

Agree.
Statement 2: "A dynamically created object will call it's destructor when it
is made a target of a delete".

Does not make sense to me. Would not this result in an endless loop? (ie.
delete calls destructor and within destructor it calls delete, which in turn
calls the destructor again and so on....)

Any comments appreciated.

asasas

[Andrew Ward]

Where are these statements from?
You have to differentiate between objects created dynamically on the heap
with the 'new' operator, and objects created on the stack in a scope.
Using the delete operator instructs the program to call the destructor of
the class and then free the memory for the object. Objects that simply go
out of scope implicitely have the same process performed on them.
"Newsnet Customer" <ni********@ipr imus.com.au> wrote in message
news:3f******** @news.iprimus.c om.au...

Hi,

Statement 1: "A dynamically created local object will call it's destructor
method when it goes out of scope when a procedure returms"

Agree.
Statement 2: "A dynamically created object will call it's destructor when it is made a target of a delete".

Does not make sense to me. Would not this result in an endless loop? (ie.
delete calls destructor and within destructor it calls delete, which in turn calls the destructor again and so on....)

Any comments appreciated.

asasas

[John Harrison]

"Newsnet Customer" <ni********@ipr imus.com.au> wrote in message
news:3f******** @news.iprimus.c om.au...

Hi,

Statement 1: "A dynamically created local object will call it's destructor
method when it goes out of scope when a procedure returms"

Agree.
Statement 2: "A dynamically created object will call it's destructor when it is made a target of a delete".

Does not make sense to me. Would not this result in an endless loop? (ie.
delete calls destructor and within destructor it calls delete, which in turn calls the destructor again and so on....)

Any comments appreciated.

asasas

Destructor does not call delete, so there is no loop.

john

[Josephine Schafer]

"Newsnet Customer" <ni********@ipr imus.com.au> wrote in message
news:3f******** @news.iprimus.c om.au...

Hi,

Statement 1: "A dynamically created local object will call it's destructor
method when it goes out of scope when a procedure returms"

Agree.
Consider this code -

#include <iostream>
class A{
public:
A()
{
}
~A()
{
std::cout << "Inside D'tor";
}
};

void f()
{
A a;
A *ptrA = new A;
}

int main ()
{
f ();
}

If you mean that when f() returns two destructors will be called then it's
wrong.
Destructor would be called only for the object created on the heap.
In fact this is a memory leak.

Statement 2: "A dynamically created object will call it's destructor when it is made a target of a delete".

That's true.

Does not make sense to me. Would not this result in an endless loop? (ie.
delete calls destructor and within destructor it calls delete, which in turn calls the destructor again and so on....)

Destructor does not call delete unless in your destructor you write -
delete this;

HTH,
J.Schafer

[Josephine Schafer]

Destructor would be called only for the object created on the heap.

I meant stack ofcourse ;-).

[Newsnet Customer]

> "Newsnet Customer" <ni********@ipr imus.com.au> wrote in message

news:3f******** @news.iprimus.c om.au...

Hi,

Statement 1: "A dynamically created local object will call it's destructor method when it goes out of scope when a procedure returms"

Agree.
Statement 2: "A dynamically created object will call it's destructor when

it

is made a target of a delete".

Does not make sense to me. Would not this result in an endless loop?

(ie. delete calls destructor and within destructor it calls delete, which in

turn

calls the destructor again and so on....)

Any comments appreciated.

asasas

Destructor does not call delete, so there is no loop.

john

Generally speaking, you have a delete in a destructor method. That said, a
delete calls the destructor and the endless cycles continues. I'm sure there
is something im missing.
sasas

[Newsnet Customer]

Where are these statements from?
You have to differentiate between objects created dynamically on the heap
with the 'new' operator, and objects created on the stack in a scope.
Using the delete operator instructs the program to call the destructor of
the class and then free the memory for the object.

and whats USUALLY in the destructor method? a delete statement also,and
hence the loop.
sasasasas

[Peter van Merkerk]

> > Destructor does not call delete, so there is no loop.

Generally speaking, you have a delete in a destructor method. That

said, a delete calls the destructor and the endless cycles continues. I'm sure there is something im missing.

A destructor never calls the delete operator on itself (this), hence no
endless loop. In a destructor the delete operator (if any) is only used
for other objects owned by that class instance, not for itself.

--
Peter van Merkerk
peter.van.merke rk(at)dse.nl

[Scott Condit]

Newsnet Customer wrote:

Where are these statements from?
You have to differentiate between objects created dynamically on the heap
with the 'new' operator, and objects created on the stack in a scope.
Using the delete operator instructs the program to call the destructor of
the class and then free the memory for the object.

and whats USUALLY in the destructor method? a delete statement also,and
hence the loop.

What loop?

delete statements can often be found in destructors, but they
do not target the object whose destructor it is.

S

[Newsnet Customer]

Destructor would be called only for the object created on the heap.

I meant stack ofcourse ;-).

incorrect. as indicated in statement 1. an object's (dynamically created
....meaning HEAP) destructor is called when the object goes out of scope.