TITLE: Deleting "this"

PROBLEM: amb@Apple.COM (A. Michael Burbidge)

Even though it works, I am still wondering whether the official language
specification says anything about "delete this;" from a constructor. I can't
find anything in the ARM about it.


RESPONSE: jamshid@ut-emx.uucp (Jamshid Afshar)

I can't find anything restricting `delete this;' from constructors
either, so I believe it is okay.

[stuff deleted]

Also make sure that neither you nor the client can derive any new
classes from this set of classes.  It's no fun being in a constructor
whose `this' was deleted during the construction of a base class :-).
An easy way to ensure no stack objects can be created *and* that a
user cannot derive a new class is to make the destuctor (or all
constructors) `private'.


RESPONSE: jimad@microsoft.com (Jim ADCOCK)

On the contrary, in general this *will not* work.  If it not explicitly
made illegal, then it should be.  Certainly any use of inheritence
virtual functions, etc, ...


RESPONSE: jamshid@emx.utexas.edu (Jamshid Afshar)

[This is a repost.  We had a system crash and I don't believe my
original followup got out -- please let me know if you're seeing
this twice.]

Jim failed to quote, and apparently failed to read, the rest of my
article where I discuss the problem and offer a remedy:

[stuff deleted]

Michael asked what the "official language specs" have to say about it,
and I answered that the ARM apparently doesn't seem to restrict it.  I
am not on the ANSI C++ committee so I do not know if restrictions are
being considered.  Note, I'm not arguing that it is a good practice
(in general, I would prefer a flag and allowing creation only with a
static member function until exception handling).

Jim says that it should be made illegal, but I don't agree with this
change for a couple of reasons.  It is perfectly safe in leaf classes
(and it's easy for the programmer to ensure it is a leaf class or for
the compiler to warn that it might not be).  Also, the change would
not prevent a `delete this' from happening during construction -- the
constructor could simply call another member function which does it.