On Sunday, 1 March 2015 at 16:54:15 UTC, Zach the Mystic wrote:
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/[email protected]
...and:
http://forum.dlang.org/post/[email protected]
That's not applicable here though. The compiler doesn't know
we're doing reference counting, so it cannot insert
AddRef/Release calls.
