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From: "Richard Smith" <richard@ex-parrot.com>
Newsgroups: comp.std.c++
Subject: Re: why doesn't delete NULL the pointer?
Date: Mon, 25 Mar 2002 19:27:35 GMT
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"Pedro Sam" <p2sam@uwaterloo.ca> wrote in message
news:a7j7vg$78s$1@watserv3.uwaterloo.ca...
> Hi all,
>
> I'm curious about the delete operator and NULL pointers.  Why doesn't
> the standard require that the delete operator to set the pointer's value
> to NULL?
>
> If the pointer is NULL, then if someone comes along and try to access
> that pointer, it would crash with a segfault, instead of reading garbage
> ( or even worse, write over some memory ).

Consider the following example:

    class bar { /* ... */ };

    class foo
    {
    public:
     ~foo()
      {
        for( set::set< bar * >::iterator i( s.begin() );
             i != s.end(); ++i )
          delete *i;
      }
    private:
      std::set< bar * > s;
    };


i) std::set's iterators are all const_iterators -- even the one named
'iterator' so you cannot modifiy the value.

ii) if you did nullify the iterators value (using, say, a const_cast) bad
things would happen because the set would have been tricked into containing
multiple equal values.

--
Richard Smith


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