> On 6 Mar 2018, at 17:08, Ivan Vučica <[email protected]> wrote: > > Hi, > > I was explaining refcounting and NSAutoreleasePool to someone, and I thought > referencing GNUstep might be useful to explain the correct mental model of > the behavior. > > But I'm confused about -drain in the non-ARC implementation: > > https://github.com/gnustep/libs-base/blob/b8185fa6c13172436c070ab3bf60b3f12bce433b/Source/NSAutoreleasePool.m#L546 > > Won't equating drain and dealloc mean that pools will misbehave, and that > after [pool drain], the incorrect pool will get populated (and later drained)? > > Am I correctly interpreting that this happens? If so, is it correct that this > happens? > > NSAutoreleasePool * outerPool = [NSAutoreleasePool new]; > [[NSObject new] autorelease]; // object 0 added to outerPool > > NSAutoreleasePool * innerPool = [NSAutoreleasePool new]; > [[NSObject new] autorelease]; // object 1 added to innerPool > [innerPool drain]; // object 1 released; outerPool is the closest pool > [[NSObject new] autorelease]; // object 2 added to outerPool > [innerPool release]; // object 2 released, object 0 released; new pool > created as the closest pool > > [outerPool release]; // no objects released; new pool created as the closest > pool > > Unless I am missing something, object 0 would be released early here?
According to Apple, the -drain method is a synonym for -release (or -dealloc since you don't retain autorelease pools). So yes, if youi drain a pool the next time an object is autoreleased it goes into the parent pool of the one you drained. Your code above should crash at the point where you call [innerPool release] since you are sending the -release message to a deallocated object. I think the -drain method name is unintuitive. To me it sounds like it ought to do the same as the gnustep-specific -emptyPool method (a more efficient equivalent to draining/releasing the pool and immediately creating a new one). _______________________________________________ Gnustep-dev mailing list [email protected] https://lists.gnu.org/mailman/listinfo/gnustep-dev
