On 2010-02-14 15:41:30 -0500, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> said:
Michel Fortin wrote:
Hum, what's the syntax for placement delete?
There is no need for placement delete. There will be a function clear()
in object.d that only calls the destructor. (That is needed
regardless.) You can carry deallocation with your own API functions.
What's the point in wasting a function name only to call the
destructor? Why not just allow "object.~this()"?
Also, if you really want to put an object back in it's initial state,
you could call both the destructor and the constructor. Anything else
is going to break the object's invariant. I think it's best to leave
breaking the object's invariants to a special syntax, hence
"object.~this()".
So why remove custom allocators? Those can be useful to catch all
allocations of a specific class in an existing code base and improve it
for some specific needs without having to change code everywhere. I'd
rather see that better generalized (we talked about making 'new' a
template earlier).
There are many problems with custom allocators. They hook the syntax
and do something that's unbecoming. new T must place T on the
garbage-collected heap, period. That gives the guarantee that the
object has infinite lifetime and therefore dependable behavior. If the
same syntax can be used to implement various other semantics, you can't
count on anything in generic code.
Well, I agree that new should have dependable semantics. I disagree
about it being always from a GC-allocated block. There are other ways
to create infinite lifetime behaviour, like a smart pointer. Of course
you can't do that with 'new' as it stands today because you can't make
it return something else than a crude pointer. That's what need to be
fixed I think.
You could say that having placement-new fixes that problem, and in a
way it does because it allows you to create what I've described as a
separate function. Except you have to use a different syntax to create
the object which makes things less transparent (especially with generic
code).
Also, having placement-new and regular-new share the almost same syntax
isn't a good way to say that 'new' has dependable semantics. I think
there is a better syntax for calling the constructor: "object.this()".
Also, why remove anonymous classes?
Walter thinks we need to keep them.
Is that your reason for wanting them removed? :-)
--
Michel Fortin
michel.for...@michelf.com
http://michelf.com/
