[Effective-cpp] Item 34: Understand How to Combine C++ and C in the Same Program.

[Adrian Fagg]

> -----Original Message-----
> From: Klitos Kyriacou [mailto:Klitos.Kyriacou at reuters.com]

> > Adding virtual functions, 
> > however, causes structs to use a different memory layout, and 
> > transfer is 
> > no longer possible.
> 
> Is this necessarily true? If you slice a derived class that 
> has virtual
> functions into a POD, C struct (and pass it to a C function) won't the
> resulting struct have the same memory layout as the original?

There are two ways to add member functions - derivation and conditional
compilation.
The latter would be vulnerable to change if virtual functions were included,
the former would not.

When you say slice, presumably you're not talking about copying, just
casting a pointer in this case? Either way, I would have thought that you
must be right - if the same struct declaration leads to the same thing in C
and C++ with compatible compiler settings, then surely the cast must work
without surprises?

Regards,

Adrian

Work: mailto:adrianf at evaluategroup.com
Home: mailto:adrian.fagg at ntlworld.com

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