{
  "id": 2096323,
  "title": "Swift ARC Doesn’t Scan the Heap — I Removed strong_release from SIL to Prove It",
  "url": "https://urgent.news/2026/08/20/swift-arc-doesnt-scan-the-heap-i-removed-strong-release-from-sil-to",
  "topic": "tech",
  "section": "Tech",
  "published": "2026-08-20T07:35:56.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/_a3620048b828cbaa5d742/swift-arc-doesnt-scan-the-heap-i-removed-strongrelease-from-sil-to-prove-it-oed"
  },
  "original_language": "en",
  "account": "This report examines the inner workings of Swift's automatic reference counting (ARC) system, contrasting it with a background service that periodically scans memory. Swift ARC operates by analyzing ownership and value lifetimes, represented as operations such as copy_value, destroy_value, strong_retain, and strong_release in the intermediate representation SIL. These operations are lowered to runtime behavior like swift_retain and swift_release. When a release brings an object's strong reference count to zero, destruction begins on that execution path.\n\nA test case was created to verify that removing the strong_release operation breaks the reference count chain, causing the object to remain alive and leading to a significant increase in memory usage. The SIL code for the original and modified versions of the test case are provided for comparison. The experiment demonstrates that the strong_release operation is critical for the proper functioning of Swift ARC.",
  "summary": "Also available: Korean version · Source code and reproducible experiments A source-to-runtime experiment with Swift 6.3.1: inspect ownership in SIL, delete one strong_release , measure the resulting leak, compare weak-reference lowering, and follow the call stack into the Swift runtime. Swift ARC is sometimes explained as if it were a background service that periodically scans memory and frees…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}