Encouraging memory efficiency

[John Colvin via Digitalmars-d]

On Thursday, 17 July 2014 at 16:28:00 UTC, Tero wrote:
> Just watched Don's DConf 2014 talk where he said D has to be 
> ruthless about
> memory inefficiency. Here's one thing that I think could help 
> avoid unnecessary garbage: built-in syntax for this:
>
> import core.stdc.stdlib : alloca;
> ubyte[] buffer = (cast(ubyte*) alloca(bufsize)) [0 .. bufsize];
>
> Often bufsize is not known at compile-time but it won't change 
> after the buffer
> allocation. So there's no reason to create garbage other than 
> the *inconvenience*
> of using alloca. Allocating in the stack seems ideal so I'd 
> encourage that by a
> clean syntax. I keep missing this feature.

When talking about allocations:

The stack is just a fixed size chunk of pre-allocated memory with 
complicated rules and caveats for use. It's only advantage as a 
place for general purpose allocation is that it's "hot" memory, 
i.e. it's normally already in cache due to it's locality. The 
fact that it is 1) pre-allocated and 2) eagerly de-allocates on 
exiting a function can be easily implemented in any allocation 
scheme.