Bug Archeology: Solving a decade-old Swift/C++ mystery (with LLMs)
In a blog post titled "Bug Archeology: Solving a decade-old Swift/C++ mystery (with LLMs)", developer Sam Khawase recounts using large language models (LLMs) to track down a long-standing crash in Swift/C++ interop. The bug manifested as a sporadic crash in audio processing code on Apple Silicon Macs, specifically when using CoreAudio's AudioUnit framework. Despite numerous bug reports over ten years, the root cause remained elusive. Khawase fed crash logs and code snippets into an LLM, which suggested checking for memory alignment issues. Following this lead, he discovered that a C++ struct used in Swift was missing the `__attribute__((aligned(16)))` specifier, causing misaligned memory access on ARM64. The fix was a one-line change. The post highlights how LLMs can assist in debugging by connecting disparate clues, though it notes that the LLM did not solve it alone—it provided a hypothesis that the developer verified. The bug was resolved in a personal project, but the finding could benefit other developers facing similar crashes in CoreAudio or other audio frameworks.
Shows LLMs can help debug obscure, long-standing bugs by suggesting hypotheses from crash data.