@class NSPointerArray, NSMutableSet, NSObject; @protocol OS_dispatch_group; @interface _SYQuiescenceObserver : NSObject { NSPointerArray *_quiescenceQueues; NSObject<OS_dispatch_group> *_allocationGroup; NSMutableSet *_allocations; } + (id)sharedInstance; + (BOOL)isQuiescenceEnabled; + (void)setQuiescenceEnabled:(BOOL)a0; - (id)init; - (void)registerQueue:(id)a0; - (void).cxx_destruct; - (void)decrementAllocationCount:(id)a0; - (void)incrementAllocationCount:(id)a0; - (void)notifyOnDeallocationComplete:(id /* block */)a0; - (void)notifyOnQuiescence:(id /* block */)a0; - (BOOL)waitForDeallocationCompleteWithTimeout:(double)a0; - (BOOL)waitForQuiescenceWithTimeout:(double)a0; @end