NSAutoreleasePool drain/dealloc

[Ivan Vučica]

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?