Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hplsla!jima
From: jima@hplsla.HP.COM (Jim Adcock)
Newsgroups: comp.lang.c++
Subject: Re: Question: Object transformations in C++
Message-ID: <6590176@hplsla.HP.COM>
Date: 29 Jun 89 17:41:34 GMT
References: <4413@druco.ATT.COM>
Organization: HP Lake Stevens, WA
Lines: 29

Regards trm's comments --

The example shows what I was thinking of in terms of using new, otherwise
the same as my examples using "this."

But, I think maybe he's wrong about this technique being safe -- at least
it confused the hell out of my compiler producing:


Constructing Base.
Constructing Base.
Constructing Derived.
Called Base::f()
Called Derived::f()
Called Derived::f()

-- which is surely wrong by any standards.

I would expect b.f() to be ill-defined, compiler dependent, depending on
whether a compiler chooses to evaluate this at compile time or run
time.  For this to work as trm says would seem to imply virtual functions
*always* have to be evaluated at run time -- which would also prevent
their ever being in-line substituted.

I think this would be wrong -- making people who don't play hack games
with objects pay a substantial performance penelty for people who do play
hack games with objects!

Can we have this language issue clarified, please?