* Add test for emptying autorelease pool
* Fix arc autorelease pool emptying when adding further references
When releasing a reference in the arc autorelease pool, it is
possible and anticipated that new references may added to the pool.
This fix addresses an edge case where releasing a reference in the
same pool page as the stop position can add more references which
cause the insertion of a new page and emptyPool() returns early
after emptying the new page.
This fixes a regression in 73132a6 (#200) where nil was returned
from a retain call after the object begins deallocating. Normal
retains of a deallocating object are still expected to return an
instance pointer inside its dealloc method and code compiled with ARC
will generate calls to objc_storeStrong() when a block captures the
self pointer inside the dealloc method.
The previous checks for a deallocating object with negative reference count did not work because:
1. the sign bit has to be recreated as was happening in objc_delete_weak_refs()
2. there was no distinction between a saturated count and a negative reference count
refcount_max now indicates when the refcount has saturated and should no longer be mutated.
An underflow to -1 still maps to refcount_mask, allowing us to detect when an object is supposed to be deallocated.
Neither objc_release_fast_no_destroy_np() nor objc_retain_fast_np() mutate the refcount when it is one of those values, so the comment in objc_delete_weak_refs() was adjusted.
This bug is also present in the original version:
When removing a WeakRef from the map, we use its obj field to find the
key, but the obj field has already been zeroed by this point and so we
end up leaving dangling pointers in the map.
Graham--M
Frederik Seiffert
David Chisnall
Dustin L. Howett
David Chisnall