Destructor semantics

[foobar]

Steven Schveighoffer Wrote:

> On Tue, 10 Aug 2010 16:33:08 -0400, foo <foo at bar.com> wrote:
> 
> > In light on recent discussions of clear() and the distructor it seems to  
> > me that we are going backwards from one of D's great improvements over  
> > C++ - the difference in semantics between structs and classes.
> >
> > IMO, instead of enhancing class desteructors they should be completely  
> > removed and only allowed on structs with deterministic semantics and all  
> > uses cases of class desteructors should be replaced with structs.
> > Examples:
> > class SocketConnection : Connection {
> > // struct instance allocated inline
> > SocketHandle handle;
> > ...
> > }
> >
> > OR:
> >
> > class SocketConnection : Connection {
> > struct {
> >    this()  { acquireHandle(); }
> >   ~this() { releaseHandle(); }
> > } handle;
> > ...
> > }
> >
> > The suggested semantics of the above code would be that creating a
> > SocketConnection object would also construct a SocketHandle as part of  
> > the object's memory and in turn that would call the struct's ctor.
> > On destruction of the object, the struct member would be also destructed  
> > and it's d-tor is called. This is safe since the struct is part of the  
> > same memory as the object.
> >
> > in short, struct instances should be treated just like built-in types.
> >
> 
> That doesn't help.  deterministic destruction is not a struct-vs-class  
> problem, its a GC-vs-manual-memory problem.  A struct on the heap that is  
> finalized by the GC has the same issues as a class destructor.  In fact,  
> struct destructors are not currently called when they are heap-allocated  
> because the GC has no idea what is stored in those memory locations.
> 
> -Steve

Let me add to the above, that the GC should NOT manage structs allocated on the heap. structs should only provide deterministic semantics.