How does autorelease work under the hood in ARC-enabled Objective-C?

Autorelease queues objects for deferred release at pool drain time.

ARC converts autorelease into calls to objc_autoreleasePoolPush/Pop. Each thread maintains a stack of autorelease pools. Objects added are stored in a per-thread pool. When the pool drains, all objects are sent release messages in batch. This reduces memory churn but can cause spikes if misused in loops.