Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!usc!apple!snorkelwacker!bloom-beacon!athena.mit.edu!bjaspan
From: bjaspan@athena.mit.edu (Barr3y Jaspan)
Newsgroups: comp.lang.c++
Subject: Re: this in Heap-/Stack Objects
Message-ID: <1990Oct9.173642.5187@athena.mit.edu>
Date: 9 Oct 90 17:36:42 GMT
References: <1990Oct9.162831@jellosub.luftfahrt.uni-stuttgart.de>
Sender: daemon@athena.mit.edu (Mr Background)
Reply-To: bjaspan@athena.mit.edu (Barr3y Jaspan)
Organization: Massachusetts Institute of Technology
Lines: 19

|> "... code is secretly generated in a constructor to differ-
|> entiate between objects created on the stack (the value of
|> 'this' when the constructor is called is non-zero) and objects
|> created on the free store (the value of 'this' when the con-
|> structor is called is zero)..."

Ack!  Retch!

Perhaps he is right about a particular compiler on a particular machine, but
that does *not* sound like something you can depend on across machines and
implementations.  "Code is secretly generated" for a reason, namely, to hide
an implementation detail.

(BTW, I can tell you that the compilers I've worked with (g++ and cfront 2.0)
have an implicit argument to member functions that conveys the information you
mentioned.  The compiler should not allow you to access it, however.)


Barr3y Jaspan, bjaspan@athena.mit.edu