std.allocator needs your help

[Manu]

On 24 September 2013 01:02, Andrei Alexandrescu <
SeeWebsiteForEmail at erdani.org> wrote:

> On 9/23/13 7:50 AM, Manu wrote:
>
>> delete is important if your class is being allocated by a pool or
>> something...
>>
>
> It's important as an API function, but not as a language primitive. "new"
> should also have been a function.


I like operator new. It goes blue, and the statement isn't riddled with
exclamation marks.
Imagine if new was a template (it would have to be a template). Allocating
a template would require nested template syntax every time, which is pretty
ugly.

  X x = new!(X!arg(args...)); // ewoo, paren spam...

 But you said before, people won't use 'new' if they are using an
>> allocator. I'm really not sure that's a good idea.
>>
>
> I don't see another way if people are to define and use multiple
> allocators.


Well if an allocator is somehow associated with a class/struct, then 'new
MyClass' would invoke that allocator.
If you:
  pushThreadAllocator(myAllocator);
  X x = new X;
  popThreadAllocator();

Then new will use your thread-local allocator.
Continue for global, fiber, etc.

Maybe there's opportunity for 'scope' to offer some nice convenience here?

 Most people (library authors!) don't actually care about their memory
>> allocation, they will continue to use 'new', just because it's a keyword.
>>
>
> "new considered harmful" etc.
>
>
>  It also screws with generic code; X should be allocated with 'new', but
>> Y should be allocated with yAllocator.alloc()?
>> What if you decide that Z, which allocates with 'new', becomes a problem
>> and you want to switch it into a pool? You now need to track down every
>> instance of 'new Z', and change it.
>>
>
> We can only improve that situation by allowing people to replace the
> global allocator with their own allocators. Again, there's a disconnect
> here - I'm discussing "how to make it easy for people to define allocators"
> and you discuss "how to make it possible for people to plug allocators,
> once defined, as the global allocator". These are two distinct endeavors.
> At the level I'm at, I'm concerned with making good allocators easy to
> implement. You may say you don't care, and that's good feedback, but it's
> what I have for the time being.


Well, I'm discussing "how do people affect/override 'new' in various
circumstances?"

But sure, I said before, if we're limiting this discussion to the API of an
allocator then it looks fine, I see no obvious issues.
But I think the question requires consideration of the intended goal to
make informed decisions about the design, even at this level.
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