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From: vaughan@mcc.com (Paul Vaughan)
Newsgroups: comp.lang.c++
Subject: Re: Objective suicide
Message-ID: <9299@cadillac.CAD.MCC.COM>
Date: 29 Jun 90 14:58:35 GMT
References: <685@dyndata.UUCP> <276@taumet.com>
Sender: news@cadillac.CAD.MCC.COM
Reply-To: vaughan@mcc.com (Paul Vaughan)
Organization: MCC VLSI CAD Program
Lines: 48
In-reply-to: steve@taumet.com (Stephen Clamage)


   From: steve@taumet.com (Stephen Clamage)
   
   In article <685@dyndata.UUCP> dan@dyndata.UUCP (Dan Everhart) writes:
   >Is it kosher for an object to delete itself?  To wit:
   >
   >class Obj
   >   {
   >   /* ... */
   >   void Suicide () { /* ... */  delete this; }
   >   /* ... */
   >   }

   Yes, but do be careful, as noted in your full example.  I have done this
   in a class destructor, but would not do it in a normal member function.
   After the delete, there is no guarantee that the class data makes any
   sense, and in particular that the virtual table is intact!  So a later
   destructor may try to operate with garbage.  This is a particular
   worry with virtual destructors when the virtual table is trashed.

I'm having trouble making sense out of this.  One reason to have
objects destruct themselves is for referencing counting, eg.

void Foo::UnRef() {
  count -= 1;
  if(!count) delete this;
}

Of course it's important that the code (object, whatever) that thought
it had a reference not use the pointer after calling UnRef.  Also,
it's important that you don't execute anything that needs object data
in the UnRef function after you delete this.  Other than these
considerations, I'm not aware of any reason not to delete this from a
regular member function.  

You would clearly never want to do this

Foo::~Foo() { . . .
	delete this;
}

First, it's already being deleted, second it would cause double
deallocation.  I'm assuming that's not what you meant, but that's what
it sounded like.


 Paul Vaughan, MCC CAD Program | ARPA: vaughan@mcc.com | Phone: [512] 338-3639
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