Re: using D without GC

[Andrea Fontana via Digitalmars-d-learn]

On Sunday, 7 June 2015 at 16:25:29 UTC, Oleg B wrote:

No just reserve some memory and preallocate the buffer you want before using it. It'll be a lot faster and cheaper.

I know, it's only for test.

You shouldn't be using delete or new for that matter.
You should be using malloc + free. And emplace.

auto myalloc(T)( size_t count )
{
    struct Impl{ size_t len; void* ptr; }
    union Wrap { Impl impl; T[] arr; }

auto ret = Wrap( Impl( count, calloc( count, T.sizeof ) ) ).arr;

    enforce( ret.ptr !is null );
    return ret;
}

class Bar
{
    float[] buf;
    this() { buf = myalloc!float( 65536 ); }
    ~this() { free(buf.ptr); }
}

For simple types arrays all clear. Emplace realization not trivial for me yet. As I understand correctly it concerns placing initial values of struct for example or values before calling ctor in place to array segment without copying?

But what I need use for class objects?

class Foo
{
    Bar[] buf;

    this()
    {
        buf = myalloc!Bar( 100 ); // I think it's ok
        foreach( ref b; buf )

b = new Bar; // but calloc can't initialize class correctly

    }

    ~this()
    {
        static if( gc_disable )
        {
            foreach( ref b; buf ) delete b;
            free(buf.ptr);
        }
    }
}

Operator new automatically allocate range in GC-manage memory? If it is whether is possible to change this behavior? It's question relates to emplace too?

I guess you should follow andrei's post about new allocators!