Re: GC for noobs

[Dicebot]

On Thursday, 27 February 2014 at 14:49:48 UTC, Szymon Gatner 
wrote:
You can disable postblit to make entity non-copyable: 
http://dlang.org/struct.html#StructPostblit

How can I then use it as a function return value? Or store in a 
container?

Actually if postblit had a bool param saying that the source is 
rvalue then moving would be possible by just resetting relevant 
fields in source object.

Yep, moving ownership is the main issue (as opposed to just 
prohibiting any copy). But returning from function is not copying 
because of D semantics and you can do some tricks because of it:

http://dpaste.dzfl.pl/99ca668a1a8d

==================================

import std.c.stdlib;

struct Unique
{
        int* data;
        
        @disable this(this);
        
        ~this()
        {
                if (data)
                        free(data);
        }
        
        Unique release()
        {
                scope(exit) this.data = null;
                return Unique(data);
        }
}

void main()
{
        Unique x1 = Unique(cast(int*) malloc(int.sizeof));
        
        // auto x2 = x1; // error
        auto x2 = x1.release();
        assert(x1.data is null);
        assert(x2.data !is null);
}