From: "R.v.Paasen" <R DOT L DOT F DOT v DOT Paasen AT stud DOT tue DOT nl>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: delete NULL?
Date: Sun, 23 Feb 1997 14:35:04 +0100
Organization: Eindhoven University of Technology, The Netherlands
Lines: 55
Message-ID: <33104788.6873@stud.tue.nl>
References: <19970216 DOT 124451 DOT 7287 DOT 0 DOT fwec AT juno DOT com> <330F6A8D DOT 643B9308 AT alcyone DOT com>
Reply-To: R DOT L DOT F DOT v DOT Paasen AT stud DOT tue DOT nl
NNTP-Posting-Host: annex1s52.urc.tue.nl
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

Erik Max Francis wrote:
> 
> Mark T Logan wrote:
> 
> > char *ptr = NULL;
> >
> > delete ptr;
> >
> > Will anything bad happen?  I have written the linked list to be as simple
> > as
> > possible, and as such only one node will ever have a pointer in it
> > pointing
> > to NULL.  This node is the dummy node at the beginning of the list, and I
> > end up calling delete on it in one of my destructors.
> 
> No.  Deleting the null pointer is guaranteed to be safe in C++.
> 
> > Do I need to avoid this?  Will this become some horrific bug much later
> > in
> > my project?
> 
> If it does, then it's a bug in your compiler.
> 

You have to be sure that ptr is initialised with NULL.

The following:
   char* prt;

   int main(void)
   { delete ptr
     return 0;
   }

will crash when the compiler doesn't initialise variables.
(i.e. set them to 0 when no init value is specified). 
The folowing will always work:

    #define size 1000
    char* ptr;
    
    int main(void)
    { ptr=new char[size];
      delete[] ptr;
      return 0;
    }

Note the delete[] for arrays that have been allocated by new!

Richard.
-- 
-------------------------------------------
email: <mailto:R DOT L DOT F DOT v DOT Paasen AT stud DOT tue DOT nl>
www:   <http://huizen.dds.nl/~buddha/>
SENDING UNSOLICITED MAIL AND JUNK MAIL IS PROHIBITED