Re: slightly interresting derrived class problem

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Mon, 29 May 2006 15:19:00 -0400

Message-ID:

<e5fhf4$5q9$1@news.datemas.de>

easy wrote:

I start off with an interface class that has no data members and a
handful of virtual functions.

First Question: is that allowed ?

Uh... Yes. Does your compiler tell you something you don't believe
it should?

I then derived from this class and it gets included into a couple of
other classes that need that interface. The derived class had a
number of data members including a struct that allow it to do its
dirty work.

OK...

When I directly access any data members (through pointers or through
public data members) in the derrived class hilarity ensues. I found
that the value returned is offset by 4 bytes( 32bits ).

for example, if I wanted:
class1.public_struct.int0
I would get
class1.public_struct.int1

That's bizarre.

more curiously this problem would only show up when i ran the release
version of the code. The debug version behaved correctly.

That sounds like an error in the compiler...

After an entire wasted morning I added an unused data member to the
very first interface class and all problems dissapeared like a fart in
the wind.

Main Question: Is this a compiler error or did I violate the standard?

To be able to tell you for sure, we'd need to see the code.

V
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