Interfacing D with C: Getting Started

[Arun Chandrasekaran]

> In D, long and ulong are always 8 bytes. This lines up with 
> most 64-bit systems under the version(Posix) umbrella, where 
> long and unsigned long are also 8 bytes. However, they are 4 
> bytes on 32-bit architectures. Moreover, they’re always 4 bytes 
> on Windows, even on a 64-bit architecture.

Why is this? How are we expected to write cross platform code 
with long/ulong? What are the alternatives?