Re: ATL Under the Hood Part 5 - C / C++ / MFC Discussion Boards

vinodcs11-Mar-08 19:00

11-Mar-08 19:00

Hi,
Pls tell me how this program works...
I set a pointer to class to Zero, but still I
can access an instance member as far as I don't access any instance variable.

<br />
#include "stdafx.h"<br />
<br />
#include <stdio.h><br />
class A<br />
{<br />
public:<br />
	int i;<br />
	void PrintMe();<br />
};<br />
 <br />
 <br />
void A::PrintMe()<br />
{<br />
	    printf("Hello World\n");<br />
}<br />
 <br />
void main()<br />
{<br />
    A* p = 0;<br />
    p->PrintMe();<br />
 <br />
}<br />

Vinod

Re: Accessing with Zero pointer

Stephen Hewitt11-Mar-08 19:13

Stephen Hewitt

11-Mar-08 19:13

The A::PrintMe function doesn't access class members and isn't virtual so the this pointer isn't used. This is perfectly legal.

Steve

Re: Accessing with Zero pointer

Maximilien12-Mar-08 3:19

Maximilien

12-Mar-08 3:19

well, I learn something everyday.

A* p = NULL;
p->PrintMe();

How does "it" know what method to call if p == NULL ?

I would have assumed that accessing a NULL point itself would have at least throw an exception at least.

Confused | :confused:

Maximilien Lincourt
Your Head A Splode - Strong Bad

Re: Accessing with Zero pointer

Stephen Hewitt13-Mar-08 13:55

Stephen Hewitt

13-Mar-08 13:55

From the following:
- The type of the pointer (A*).
- The name of the function.

The fact that the function isn't virtual means this is all the infomation needed.

Steve

Re: Accessing with Zero pointer

Rajkumar R11-Mar-08 19:14

Rajkumar R

11-Mar-08 19:14

see this[^]

It seems me, in the forum guidelines by chris, i found some thing like "check previous recent posts before asking questions", but its not there now.

Re: Accessing with Zero pointer

Michael Dunn12-Mar-08 19:50

Michael Dunn

12-Mar-08 19:50

Calling a method on p doesn't actually dereference p, it just sets this to the value of p. If PrintMe() dereferenced this, for example accessing non-static data members, then the code would crash.

ATL Under the Hood Part 5 [modified]

abhijitr11-Mar-08 18:17

abhijitr

11-Mar-08 18:17

Hi,

First of all I am very sorry as I am asking question not related to this group.

Does anybody know where are the next parts of the article "ATL Under the Hood Part 5". In the ATL series.

Or

I want to create an simple ATL COM Project from scratch, without using Appwizard.
Does anybody know about such articles?

Thanks in advance.

modified on Wednesday, March 12, 2008 2:26 AM

Re: ATL Under the Hood Part 5

Iain Clarke, Warrior Programmer12-Mar-08 0:04

Iain Clarke, Warrior Programmer

12-Mar-08 0:04

If parts 1-4 have the same author, then click on his name to see all articles written by him (or her).
If you can't see part 5, then maybe it is not written (yet).

Iain.

Iain Clarke appears because ^CPallini still cares.

crash in worker thread

lavate malllik11-Mar-08 17:56

lavate malllik

11-Mar-08 17:56

In my application some operations will run in worker therad for 15 time without crash.
But when same code will run for 30 times the application will crash.

Let me know the reasons behind this crash.

lavatema