On 4 February 2014 06:21, Adam Wilson <[email protected]> wrote:
On Mon, 03 Feb 2014 12:02:29 -0800, Andrei Alexandrescu <
[email protected]> wrote:
On 2/3/14, 6:57 AM, Frank Bauer wrote:
Anyone asking for the addition of ARC or owning pointers to D, gets
pretty much ignored. The topic is "Smart pointers instead of GC?",
remember? People here seem to be more interested in diverting to
nullable, scope and GC optimization. Telling, indeed.
I thought I made it clear that GC avoidance (which includes
considering
built-in reference counting) is a major focus of 2014.
Andrei
Andrei, I am sorry to report that anything other than complete
removal of
the GC and replacement with compiler generated ARC will be
unacceptable to
a certain, highly vocal, subset of D users. No arguments can be made
to
otherwise, regardless of validity. As far as they are concerned the
discussion of ARC vs. GC is closed and decided. ARC is the only path
forward to the bright and glorious future of D. ARC most efficiently
solves
all memory management problems ever encountered. Peer-Reviewed
Research and
the Scientific Method be damned! ALL HAIL ARC!
Sadly, although written as hyperbole, I feel that the above is fairly
close to the actual position of the ARC crowd.
Don't be a dick.
I get the impression you don't actually read my posts. And I also feel
like
you're a lot more dogmatic about this than you think I am.
I'm absolutely fine with GC in most applications, I really couldn't
give
any shits if most people want a GC. I'm not dogmatic about it, and I've
**honestly** tried to love the GC for years now.
What I'm concerned about is that I have _no option_ to use D
uninhibited
when I need to not have the GC.
These are the problems:
* GC stalls for long periods time at completely un-predictable moments.
* GC stalls become longer *and* more frequent as memory becomes less
available, and the working pool becomes larger (what a coincidence).
* Memory footprint is unknowable, what if you don't have a virtual
memory
manager? What if your total memory is measured in megabytes?
* It's not possible to know when destruction of an object will happen,
which has known workarounds (like in C#) but is also annoying in many
cases, and supports the prior point.
Conclusion:
GC is unfit for embedded systems. One of the most significant
remaining
and compelling uses for a native systems language.
The only realistic path I am aware of is to use ARC, which IS a form
of GC,
and allows a lot more flexibility in the front-end.
GC forces one very particular paradigm upon you.
ARC is a GC, but it has some complex properties __which can be
addressed in
various ways__. Unlike a GC which is entirely inflexible.
You're not happy with ARC's cleaning objects up on the spot? Something
that
many people WANT, but I understand zero cleanup times in the running
context is in other occasions a strength of GC; fine, just stick the
pointer on a dead list, and free it either later during idle time, or
on
another thread. On the contrary, I haven't heard any proposal for a GC
that
would allow it to operate in carefully controlled time-slices, or
strictly
during idle-time.
Cycles are a problem with ARC? True, how much effort are you willing to
spend to mitigate the problem? None: run a secondary GC in the
background
to collect cycles (yes, there is still a GC, but it has much less work
to
do). Some: Disable background GC, manually require user specified weak
references and stuff. Note: A user-preferred combination of the 2 could
severely mitigate the workload of the background GC if it is still
desired
to handle some complex situations, or user errors.
Are there any other disadvantages to ARC? I don't know of them if
there are.
Is far as I can tell, an ARC collector could provide identical
convenience
as the existing GC for anyone that simply doesn't care. It would also
seem
that it could provide significantly more options and control for those
that
do.
I am _yet to hear anyone present a realistic path forwards using any
form
of GC_, so what else do I have to go with? Until I know of any other
path
forward, I'll stand behind the only one I can see.
You're just repeating "I don't care about something that a significant
subset of D developers do care about, and I don't think any changes
should
be made to support them".
As far as I know, a switch to ARC could be done in a way that 'regular'
users don't lose anything, or even notice... why is that so offensive?
