structs vs classes

[Simen kjaeraas]

Jim <bitcirkel at yahoo.com> wrote:


> "All class-based objects are dynamically allocated—unlike in C++, there  
> is no way to allocate a class object on the stack."
> - The D Programming Language, chapter 6.

That would probably be better written as "there is no built-in way to
allocate a class object on the stack." D is a pragmatic system programming
language. If you want to treat this blob of memory as a Foo, and you're
willing to jump through some hoops, it can be done. But the language does
not encourage this.

Like I said, putting a class on the stack is an unsafe thing to do (see
http://en.wikipedia.org/wiki/Object_slicing), and it was deemed that the
language should not directly support such an idiom. It is still doable in
a library.


> The lightweight nature of structs is very appealing though. I like that  
> very much of course. Couldn't that be optimised by the compiler alone  
> knowing that a class wasn't derived?

Perhaps, in some cases. Final classes might. If a class is not marked
final, someone might derive from it, include this from a DLL or otherwise,
and boom goes the program.

-- 
Simen