Jason House wrote:
Andrei Alexandrescu Wrote:
I've discussed something with Walter today and thought I'd share it here.
The possibility of using D without a garbage collector was always
looming and has been used to placate naysayers ("you can call malloc if
you want" etc.) but that opportunity has not been realized in a seamless
manner. As soon as you concatenate arrays, add to a hash, or create an
object, you will call into the GC.
So I'm thinking there should be a flag -nogc that enables a different
model of memory allocation. Here's the steps we need to take:
1. Put array definitions in object.d. Have the compiler rewrite "T[]" ->
".Array!(T)" and "[ a, b, c ]" -> ".Array!(typeof(a))(a, b, c)". I think
superdan suggested that when he wasn't busy cursing :o).
I like that translation since it can allow customization. How will the type
system handle Array!(const(T)) and const(Array!T)? They're no longer implicitly
convertible.
We will need to accommodate multiple implicit conversions somehow anyway
(e.g. multiple alias this entries). This is a great question because it
illustrates how segregating arrays out of the language challenges the
magic that made them "special" and democratizes good features such that
other types can benefit of them too.
2. Do the similar thing for associative arrays.
3. Have two object.d at hand: one is "normal" and uses garbage
collection, the other (call it object_nogc.d) has an entirely different
definition for arrays, hashes, and Object.
A version statement seems more powerful. Standard libraries may need changes
too.
4. The definition of Object in object_nogc.d includes a reference count
member for intrusive refcounting.
That's still a method of garbage collecting! -nogc is kind of misleading...
Yah, I agree.
5. Define a Ref!(T) struct in object_nogc.d that does intrusive
reference counting against T using ctors and dtor.
6. At this point we already have a usable, credible no-gc offering: just
use object_nogc.d instead of object.d and instead of "new Widget(args)"
use "Ref!(Widget)(args)".
Ick... Please make this hijack the default new behavior.
Agreed.
Andrei
