Am Sat, 7 Dec 2013 08:43:53 -0800 schrieb "H. S. Teoh" <hst...@quickfur.ath.cx>:
> On Sat, Dec 07, 2013 at 10:08:25AM +0100, Johannes Pfau wrote: > [...] > > It looks like we actually generate a closure here which contains the > > this pointer instead of directly using the struct as a context > > pointer. That is probably an optimization bug in dmd, but it > > doesn't matter in this case as the problem would exist for closures > > and normal delegates. > > The problem is that delegates are never passed the this pointer from > the caller; it is assumed that it's part of their context. You never > write `myStruct.dg(args)`, but simply `dg(args)`. But by the time the > delegate is invoked, you can't guarantee that `this` is still valid. > Only the caller knows what copy of the struct it still holds, but > this isn't communicated to the delegate. (On second thought, even if > it *did* pass the updated `this` to the delegate, it would still be > wrong, because there could be multiple copies of the struct by then, > and who knows which copy the delegate was supposed to be operating > on?) True, but that's not what I meant ;-) I always get the terminology related to closures wrong so sorry if that didn't make sense. What I meant is this: In the first example I posted, http://dpaste.dzfl.pl/433c0a3d the delegate does not access _function variables_. It only accesses the this pointer. So there's no need for it to be a real closure and allocate memory, it could instead be a normal delegate with the context pointer simply set to the this pointer at the moment the delegate is created.
