Re: Pointers - *p++

From:

"Daniel T." <daniel_t@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Sun, 01 Nov 2009 19:19:59 -0500

Message-ID:

<daniel_t-8359C7.19195901112009@earthlink.us.supernews.com>

crystal twix <jonwongfanclub@gmail.com> wrote:

Hi. I'm trying to understand what my professor says when he refers to
declaring a pointer, and seeing the operator precedence and seeing
what happens when we do things like

p++
*p++
(*p)++ etc,

but he starts out with this declaration
int *p = (int *)0;

Although my compiler does not complain, when I try to do something
like
cout << *p;

I get a Bus Error on the console (I'm using Xcode). What am I doing
wrong here? Thanks.

A pointer that contains the value '0' is a special case. It basically
means that it points to nothing and it is an error to dereference it.
This is not an error that can be caught at compile time in the general
case, so your program is notifying you of the error during runtime.

int main() {
   int* nothing = 0;
   int* something = new int(10);

   cout << *something << '\n'; // prints "10".
   cout << *nothing << '\n'; // undefined behavior, if you are lucky
                             // your program will crash.
}