From: "Philippe A. Bouchard" <philippeb@[...].ca> 


>  > I'm not sure if this ptr<> type under discussion works this way, but in
>  > general you can't conformingly use char* arithmetic with offsets to
find
>  > the sub-parts of non-POD types.
> 
>  The offsets are what static_cast<>s return.

No, static_cast<>  returns pointers, not offsets.

The standard doesn't guarantee that the offset calculated from a given
static_cast will work again, given the same source and target types.
Actually doing the static_cast is the only portable way to find the Base*
from a Derived*. Indirection through a function pointer which does the
static_cast might be an option.

-Dave


-----------------------------------------------------------
           David Abrahams * Boost Consulting
dave@[...].com * http://www.boost-consulting.com


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