Allocating a wstring on the stack (no GC)?

[John Colvin via Digitalmars-d]

On Wednesday, 7 May 2014 at 18:26:08 UTC, Maxime 
Chevalier-Boisvert wrote:
> I have a very specific use case (JIT compiler) in which I have 
> a pre-allocated array of wchar string data stored somewhere in 
> memory. I'd like to be able to create a temporary D wstring 
> object to pass this as a "regular" string to other functions. 
> For performance reasons, it would be preferable not to 
> dynamically allocate or copy any data. Dynamically allocating 
> the strings tends to trigger the D GC which severely impacts 
> the performance.
>
> So, my question is, would it be possible for me to allocate a 
> wstring object on the stack, and manually set its string data 
> pointer and length? If so, how? Your wizardly help is much 
> appreciated.

If I read your question correctly, you just want to use wstring; 
slices in D already work how you want.

auto len = 100;
auto a = new char[len];
// a (the pointer and length) is on the stack, the new memory of 
length len is on the GC heap

auto b = a;
// b is also on the stack, with the same pointer and length as a

auto c = b[3 .. 40];
// c is also on the stack, with pointer equal to b.ptr + 3 and 
length 37