POD

[Walter Bright]

On 12/28/2012 7:37 PM, Andrei Alexandrescu wrote:
> On 12/28/12 10:12 PM, Walter Bright wrote:
>> For example, C++ disallows mixed public/private data in a POD. I've
>> never understood the reason for that restriction other than "C doesn't
>> have private fields". D doesn't propagate that aspect.
>
> The idea was to leave C++ compilers to change the order of fields in classes
> with private data for optimal layout. I don't know of any compilers that do, but
> that was the intent. PODs were not susceptible to such layout optimization
> because they had to be compatbile with C's layout.

I didn't know that, but it makes sense.

Interestingly, D's original design allowed fields in classes to be rearranged. 
This kind of fell by the wayside with the align directive.