std.allocator needs your help

[Peter Alexander]

On Sunday, 22 September 2013 at 23:49:56 UTC, Andrei Alexandrescu 
wrote:
> struct NullAllocator
> {
>     enum alignment = real.alignof;
>     enum size_t available = 0;
>     ubyte[] allocate(size_t s) shared { return null; }
>     bool expand(ref ubyte[] b, size_t minDelta, size_t 
> maxDelta) shared
>     { assert(b is null); return false; }
>     bool reallocate(ref ubyte[] b, size_t) shared
>     { assert(b is null); return false; }
>     void deallocate(ubyte[] b) shared { assert(b is null); }
>     void collect() shared { }
>     void deallocateAll() shared { }
>     static shared NullAllocator it;
> }

Does the presence of "shared" indicate that all allocators must 
be thread-safe?

Will we be able to define thread-unsafe allocators, designed for 
use on one thread for performance reasons?