All you Need to Know About Xcode Hidden Logs
summary
Explains how Xcode writes hidden logs into DerivedData as gzipped xcactivitylog files using an Apple-specific SLF encoding, where doubles are timestamps since 2001 and class names appear once with many class instances. Shows a Swift open-source parser (Spotify) that decompresses, maps numeric fields to Obj‑C headers, and emits JSON and reporters (Chrome tracing, HTML). Demonstrates numbers from real runs: project build ~40s, 3 warnings, a slow Swift file at ~39s and a target at ~119s, plus CI and DB export workflows.
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chapters (12)
- 0:00Introduction
- 0:45Report Navigator
- 12:30Encoding
- 17:07Tokenization
- 19:00Class Headers
- 21:50Project Build
- 23:10Parser
- 23:58JSON Dump
- 25:40JSON parser
- 26:20Data structure
- 32:13Reporting
- 35:10Analysis
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