Google uses Gemini to rewrite giflib from C to ABI-compatible Rust

An InfoQ China report dated October 9, 2026 describes how Google's security team used Gemini to translate giflib, a roughly 3,000-line C image library, into an ABI-compatible Rust implementation. The library is often used to decode untrusted user input without sandbox isolation. The team kept the original exported symbols and struct definitions so the Rust version could serve as a drop-in replacement for the existing shared object without requiring changes from downstream callers. After the swap, the process-isolation sandbox was disabled while latency stayed the same. The team also says it fixed an unpatched heap-write zero-day before it was publicly cataloged as CVE-2026-26740.

The migration relied on a three-stage automated feedback loop. First, a one-shot prompt asked Gemini to port the full logic of the C library to Rust. An automated differential testing engine then detected behavioral differences and fed failing execution traces back to the model to generate patches iteratively. According to the report, 200 million executions showed no functional drift. The FFI wrapper still needed manual calibration, however: early rounds introduced unsafe raw-pointer semantics, and pointer ownership and lifetime invariants had to be checked and refined by engineers. Because upstream C updates continue, the approach also creates maintenance forks. The report notes that memory-corruption bugs account for about 70% of high-severity vulnerabilities in mature C/C++ codebases, and names software engineers Bastian Kersting and Max Hils as the people behind the work.