Re: Multiple Inheritance

[borland.com!pete@decwrl.dec.com (Pete Becker)]

In article <4969@charon.cwi.nl> guido@cwi.nl (Guido van Rossum) writes:
>bs@alice.att.com (Bjarne Stroustrup) writes:
>
>>MI in C++ and elsewhere isn't perfect and it isn't a panacea, but it works
>>and it makes some styles of programming noticeably more convenient and
>>less obscure. Naturally, it can also be overused and misused, but basically
>>it works.
>
>Point taken.  However, I still worry about MI.  When MI is *not* used,
>it still imposes an overhead -- there is a "delta" offset in the vtbl
>that is added to "this" each time a virtual function is called, but
>this delta can only ever be nonzero when MI is used.  I feel that this
>is in direct conflict with the C++ philosophy that language features
>you don't use shouldn't cause overhead.
>

	That's an implementation issue, not a problem in the language
definition.  Those of us who have the luxury of being able to compile to
native code rather than C can easily avoid this problem.  Which is to say,
with our compiler, there is no MI-related overhead in any class that does
not use multiple inheritance.
	-- Pete