My Long Term Vision for the D programming language

[max haughton]

On Thursday, 25 November 2021 at 09:29:49 UTC, Elronnd wrote:
> On Thursday, 25 November 2021 at 02:32:41 UTC, max haughton 
> wrote:
>> the key thing with this scope transformation isn't stack 
>> allocation but rather moving the allocation anywhere other 
>> than the GC.
>
> I am not quite sure what you are saying.  Are you saying that:
>
> 1. The problem is moving the allocation somewhere other than 
> the gc, including potentially to the stack, or to an alternate 
> heap, or to somewhere else; or,
>
> 2. Converting allocations from gc to the stack is fine; but 
> moving them anywhere else is problematic
>
> In either case, this compiles currently and produces GC-free 
> code:
>
> @nogc:
> void f(scope int[] x);
> void g(int x, int y) { f([x, y]); }
>
> I'm not sure where you would want to move scope allocations to 
> aside from the stack, as scope guarantees LIFO, and so is the 
> perfect fit for a stack.  Perhaps an alternate stack (cf 'brk') 
> managed in druntime, to avoid stack overflow?  That would be 
> good, but is hardly a challenging transformation if you can 
> already produce regular stack allocation.

Moving an unbounded allocation to malloc and free is fine. LIFO 
is totally irrelevant.

The point is avoiding putting pressure on the GC. If you want to 
be clever you can probably come up with some hybrid arrangement 
that tries to use the stack if it can or has a buffer somewhere.