Struct beeing moved around

[Benjamin Thaut]

Am 20.05.2011 19:51, schrieb Michel Fortin:
> On 2011-05-20 13:36:58 -0400, Benjamin Thaut <code at benjamin-thaut.de> said:
>
>> What if I need a value type that may be copied, but may not be moved?
>
> I don't think that's possible. Why would you want that?
>
Lets say you want to implement a GC that is not a Mark & Sweep, and thus 
you can not do the pointer guessing game the current D GC does. So you 
have to create a reference value type, that registers itself with the GC 
when it is constructed and deregisteres itself on destruction. This 
reference type is only to be used inside functions for references that 
are constructed on the stack.

class foo { ... }

void bar(){
   foo f = new foo();
}

would become

void bar(){
   Ref!foo f = Ref!foo(new foo());
}

where Ref is:

struct Ref(T){
   T m_Ref;
   alias m_Ref this;

   this(){
     GC.addRoot(&m_Ref);
   }

   ~this(){
     GC.removeRoot(&m_Ref);
   }
}

If there is no garantuee that a struct stays on the same memory location 
within 1 Stack frame, you pretty much can not implement a other GC 
unless you hack into the compiler.

-- 
Kind Regards
Benjamin Thaut