Mallocator

[Erik Smith via Digitalmars-d]

Just a question on Mallocator and shared.  My code does a lot of 
non-GC heap allocation (malloc) for buffers, so I reached for 
Mallocator as a starting point. I propagate an Allocator type 
generically through my structs, but it is defaulted to Mallocator.

After checking with the docs & TDPL, I'm still a bit confused on 
how to deal with the shared functions in Mallocator and what the 
effect of shared functions is in this context (see code below). I 
get the error "allocate is not callable using a non-shared 
object" and I'm not sure how to resolve it.  I'm not sure if I 
should cast shared away (or how to make that work).  The docs say 
malloc/free is thread safe as far as D is concerned, so 
synchronized doesn't seem to be the answer. Forking Mallocator 
without shared solved the issue temporarily.

Also Allocators are, in general, not copyable so I should 
propagate them around as references (or pointers in struct 
members), correct?

struct Mallocator{
...
     @trusted @nogc nothrow
     void[] allocate(size_t bytes) shared
     {
         import core.stdc.stdlib : malloc;
         if (!bytes) return null;
         auto p = malloc(bytes);
         return p ? p[0 .. bytes] : null;
     }

     @system @nogc nothrow
     bool deallocate(void[] b) shared
     {
         import core.stdc.stdlib : free;
         free(b.ptr);
         return true;
     }
...
}