What does the following program do?

[Nemanja Boric]

On Tuesday, 5 December 2017 at 14:11:02 UTC, Shachar Shemesh 
wrote:
> import std.algorithm: move;
> import std.stdio;
> import std.string;
>
> class A {
>     int val;
>
>     override string toString() const {
>         return "A(%s)".format(val);
>     }
> }
>
> struct B {
>     int val;
> }
>
> void main() {
>     B b = B(12);
>     B* bp = &b;
>     B* bp2;
>
>     writefln("bp=%s bp2=%s", bp, bp2);
>     move( bp, bp2 );
>     writefln("bp=%s bp2=%s", bp, bp2);
>
>     A a1 = new A();
>     a1.val = 42;
>     A a2;
>
>     writefln("a1=%s (%s) a2=%s (%s)", a1, cast(void*)a1, a2, 
> cast(void*)a2);
>     move( a1, a2 );
>     writefln("a1=%s (%s) a2=%s (%s)", a1, cast(void*)a1, a2, 
> cast(void*)a2);
>
>     B b2;
>     writefln("b=%s b2=%s", b, b2);
>     move( b, b2 );
>     writefln("b=%s b2=%s", b, b2);
> }
>
> Answer:
> bp=7FFFAB559970 bp2=null
> bp=7FFFAB559970 bp2=7FFFAB559970
> a1=A(42) (7FD1B79E9000) a2=null (null)
> a1=A(42) (7FD1B79E9000) a2=A(42) (7FD1B79E9000)
> b=B(12) b2=B(0)
> b=B(12) b2=B(12)
>
> "move" was supposed to initialize "source" to init. This does 
> not appear to be the case. Is that a bug? Where?

```
b=B(12) b2=B(0)
b=B(12) b2=B(12)
```

bit will change if you declare destructor in your struct. As per 
the documentation:

> If T is a struct with a destructor or postblit defined, source 
> is reset to its .init value after it is moved into target, 
> otherwise it is left unchanged.

as for others I understand you have the same problem here - per 
documentation, these are not  structs with destructors, so moving 
the pointers (references) doesn't clear the source one.