RCArray is unsafe
Zach the Mystic via Digitalmars-d
digitalmars-d at puremagic.com
Sun Mar 1 08:54:14 PST 2015
On Sunday, 1 March 2015 at 15:44:49 UTC, Marc Schütz wrote:
> Walter posted an example implementation of a reference counted
> array [1], that utilizes the features introduced in DIP25 [2].
> Then, in the threads about reference counted objects, several
> people posted examples [3, 4] that broke the suggested
> optimization of eliding `opAddRef()`/`opRelease()` calls in
> certain situations.
>
> A weakness of the same kind affects DIP25, too. The core of the
> problem is borrowing (ref return as in DIP25), combined with
> manual (albeit hidden) memory management. An example to
> illustrate:
>
> struct T {
> void doSomething();
> }
> struct S {
> RCArray!T array;
> }
> void main() {
> auto s = S(RCArray!T([T()])); // s.array's refcount is
> now 1
> foo(s, s.array[0]); // pass by ref
> }
> void foo(ref S s, ref T T) {
> s.array = RCArray!T([]); // drop the old s.array
> t.doSomething(); // oops, t is gone
> }
>
> Any suggestions how to deal with this? As far as I can see,
> there are the following options:
See:
http://forum.dlang.org/post/bghjqvvrdcfqmoiyyuqz@forum.dlang.org
...and:
http://forum.dlang.org/post/cviwlkugnothraubcfgy@forum.dlang.org
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