Re: invalid offsetof from non-POD type

[kaih@khms.westfalen.de (Kai Henningsen)]

gdr@integrable-solutions.net (Gabriel Dos Reis)  wrote on 22.04.03 in <m3u1cr6xgo.fsf@uniton.integrable-solutions.net>:

> Zack Weinberg <zack@codesourcery.com> writes:
>
> | Gabriel Dos Reis <gdr@integrable-solutions.net> writes:
> |
> | > John Quigley <johnw@lowestplane.org> writes:
> | >
> | > | While it is not standards compliant code, gcc still provides the
> | > correct | result.
> | >
> | > The key issue is what do you define to be the "correct" result when you
> | > apply offsetof() to a non-POD?
> |
> | I have never really understood why the C++ standard imposes this
> | restriction.  There would seem to be a well-defined answer to the
> | question posed by offsetof(non-POD, data-member), since the data
> | member does exist in memory at a well-defined offset from the
> | beginning of the object.  If that weren't true the compiler wouldn't
> | be able to generate accesses to it.
>
> That statement is confused.

Not really. You might quibble over details, but I completely agree with  
the basic content.

> The issue isn't that the compiler couldn't return some random number.

Nobody is asking for some random number. The number asked for is well- 
defined for the cases in which one typically asks for it, as far as I can  
see.

MfG Kai