Re: [boost] reinterpret_cast : differents structs or classes with identical structural type

From: Michael Marcin (mmarcin_at_[hidden])
Date: 2007-10-02 18:50:52

Sebastian Redl wrote:
> 
> What I personally don't understand is why private members - or in fact
> all members of non-PODs - can't always be re-ordered. It's not like
> anyone should ever depend on their order. It probably was C
> compatibility that there were any guarantees at all.
> 

Why make POD-types a special case?

I like being able to depend on the order of private members. It allows 
me to nicely encapsulate my data while using SIMD operations internally.

I think that if the compiler figures out that my members would be better 
off in a different order I'd like it to warn me so I can reorder them 
myself.

I can imagine a cache performance degradation because it reorders my 
members to make the class size smaller but must access memory randomly 
in order to initialize them in the constructor in the order they 
appeared in the class definition instead of accessing them with 
ascending addresses if they were laid out the order in which they were 
specified.

- Michael Marcin