[Dlang-study] [lifetime] Initial thoughts on lifetime management

[Andrei Alexandrescu]

On 10/28/2015 11:15 AM, Marc Schütz wrote:
> On Wednesday, 28 October 2015 at 00:46:34 UTC, Andrei Alexandrescu wrote:
>> I should add here another pattern that turned problematic for our
>> older attempts in DIP74:
>>
>> C c = new C();
>> foo(c);
>>
>> int foo(scope C d) {
>>      c = new C();    // c's old instance gets deleted
>>      return d.i;        // oops! d is invalid
>> }
>>
>
> That's because global variables have potentially shared ownership. They
> need special treatment (for example, in Rust many things you can do with
> them require unsafe blocks). If `c` were an argument to `foo`, the
> compiler could catch the problem at the call site.

Interesting. Would it be sensible to add a restriction that no @rc 
object can be reachable from a global? (At least in @safe code.)

Without the restriction, it seems we always need to assume that any 
object is reachable via a global so we need to add a bunch of incs/decs.


Andrei