--- title: Google Rewrites Critical C Dependencies to Rust Using AI... description: Google's security team used Gemini to translate the giflib C image-processing library (about 3,000 lines) into an ABI-compatible Rust replacement, using a... canonical: https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Google Rewrites Critical C Dependencies to Rust Using AI and Differential Fuzzing | daily.dev og:description: Google's security team used Gemini to translate the giflib C image-processing library (about 3,000 lines) into an ABI-compatible Rust replacement, using a... og:url: https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7 og:image: https://api.daily.dev/og/posts/4Io3X5gW7.png og:image:alt: Google Rewrites Critical C Dependencies to Rust Using AI and Differential Fuzzing og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Google Rewrites Critical C Dependencies to Rust Using AI and Differential Fuzzing **[InfoQ](https://daily.dev/sources/infoq)** · 4 min read · 5 upvotes · 2 comments ## Summary Google's security team used Gemini to translate the giflib C image-processing library (about 3,000 lines) into an ABI-compatible Rust replacement, using a three-stage process: single-shot LLM translation, human review of unsound FFI pointer semantics, and automated differential fuzzing to catch discrepancies. Validation included 30 million real-world GIF regression tests and six days of differential fuzzing (200 million iterations), which caught an existing out-of-bounds write bug in the original C code. Production nodes running the Rust rewrite were immune to a subsequently disclosed CVE (CVE-2026-26740) before public cataloguing, and the switch let engineers remove legacy OS sandboxes while maintaining runtime parity and improving p99 latency. The team stresses AI-driven rewrites still need human oversight for FFI safety and ongoing maintenance against upstream C changes, and the resulting library, giflib-rs, has been open-sourced. Community discussion on Reddit and Hacker News praised the fuzzing rigor but questioned whether one-shot LLM translation scales beyond small libraries compared to deterministic transpilers like c2rust. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How did Google rewrite the giflib C library into Rust using AI? Google's security team used a three-stage automated process: a single-shot Gemini prompt ported the full C logic to Rust, human engineers fixed unsound FFI pointer and lifetime semantics, and an automated differential fuzzer fed behavioral discrepancies back into the model for iterative patching. The Rust replacement stayed ABI-compatible, preserved original exported symbols, and matched C runtime performance. _Engineers weighing AI-assisted rewrites of legacy C code can follow similar migration debates on daily.dev._ ### What testing caught bugs when Google migrated giflib from C to Rust? A validation pipeline ran mass-scale regression decoding across more than 30 million real-world GIF files for bit-for-bit rendering parity, plus six days of differential fuzzing totaling 200 million iterations comparing the C and Rust runtimes side by side. This process caught an unhandled LZW decompressor edge case and an out-of-bounds write bug that had been introduced by an earlier patch to the original C source. _Teams validating language migrations with differential fuzzing can track approaches like this on daily.dev._ ### Did rewriting giflib in Rust protect against CVE-2026-26740 before it was disclosed? Yes, production nodes running Google's Rust replacement of giflib were structurally immune to the heap out-of-bounds write vulnerability cataloged as CVE-2026-26740, which an external researcher found in the upstream C library, before the CVE was publicly disclosed. This let Google also remove legacy OS-level sandboxing previously needed to isolate image decoding, improving p99 tail latency. _Developers tracking memory-safety CVEs and Rust migrations can follow the details on daily.dev._ ## Community discussion Top comments from developers on daily.dev. **@pdfopsdev** · 0 upvotes > the interesting part isn't the LLM translation, it's that six days of differential fuzzing is what caught the OOB write in the original C. one-shot translation without that fuzzing harness doing the real verification work is just a fancy transpiler with extra steps. **@zebbediahwinstonbeck** · 0 upvotes > Wow the new sexy, say something about like "AI or Rust is better than C/C++" and get hotheads instantly erect!? Classic! But the devil is in the detail!? ## Similar posts on daily.dev - [AI Code Transforms C to Rust for Safer Software](https://daily.dev/posts/ai-code-transforms-c-to-rust-for-safer-software-xgjsw1cts) · IEEE Spectrum · 40 upvotes · 11 comments --- Tags: [#llm](https://daily.dev/tags/llm), [#rust](https://daily.dev/tags/rust), [#c](https://daily.dev/tags/c) [View this post on daily.dev](https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Google Rewrites Critical C Dependencies to Rust Using AI and Differential Fuzzing","url":"https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7"},"datePublished":"2026-09-27T14:21:21.562Z","dateModified":"2026-09-27T14:21:47.335Z","description":"Google's security team used Gemini to translate the giflib C image-processing library (about 3,000 lines) into an ABI-compatible Rust replacement, using a...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/4039ad39f18b46ced4eeb9a71bf67251?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/4039ad39f18b46ced4eeb9a71bf67251?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"InfoQ","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"InfoQ","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/afc3bced3e1e4b188dd9127017a60e0c","url":"https://daily.dev/sources/infoq"},"commentCount":2,"discussionUrl":"https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":5},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":2}],"keywords":"llm,rust,c","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"InfoQ","item":"https://daily.dev/sources/infoq"},{"@type":"ListItem","position":3,"name":"Google Rewrites Critical C Dependencies to Rust Using AI and Differential Fuzzing"}]} {"@context":"https://schema.org","@type":"WebPage","@id":"https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7","comment":[{"@type":"Comment","text":"the interesting part isn’t the LLM translation, it’s that six days of differential fuzzing is what caught the OOB write in the original C. one-shot translation without that fuzzing harness doing the real verification work is just a fancy transpiler with extra steps.","datePublished":"2026-09-29T18:21:55.106Z","url":"https://daily.dev/posts/4Io3X5gW7#c-wGY1KAj6f","author":{"@type":"Person","name":"PDFops","url":"https://daily.dev/pdfopsdev","image":"https://media.daily.dev/image/upload/s---8isRBKc--/f_auto/v1782922291/avatars/avatar_orjMeK8QKaaVZwGq7ScPz?_a=BAMAMicg0"}},{"@type":"Comment","text":"Wow the new sexy, say something about like “AI or Rust is better than C/C++” and get hotheads instantly erect!? Classic! But the devil is in the detail!?","datePublished":"2026-10-03T18:37:52.246Z","url":"https://daily.dev/posts/4Io3X5gW7#c-eGlZuNFM4","author":{"@type":"Person","name":"zebbediah winston beck","url":"https://daily.dev/zebbediahwinstonbeck","image":"https://avatars.githubusercontent.com/u/25982681?v=4"}}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/google-rewrites-critical-c-dependencies-to-rust-using-ai-and-differential-fuzzing-4io3x5gw7#faq","mainEntity":[{"@type":"Question","name":"How did Google rewrite the giflib C library into Rust using AI?","acceptedAnswer":{"@type":"Answer","text":"Google's security team used a three-stage automated process: a single-shot Gemini prompt ported the full C logic to Rust, human engineers fixed unsound FFI pointer and lifetime semantics, and an automated differential fuzzer fed behavioral discrepancies back into the model for iterative patching. The Rust replacement stayed ABI-compatible, preserved original exported symbols, and matched C runtime performance. Engineers weighing AI-assisted rewrites of legacy C code can follow similar migration debates on daily.dev."}},{"@type":"Question","name":"What testing caught bugs when Google migrated giflib from C to Rust?","acceptedAnswer":{"@type":"Answer","text":"A validation pipeline ran mass-scale regression decoding across more than 30 million real-world GIF files for bit-for-bit rendering parity, plus six days of differential fuzzing totaling 200 million iterations comparing the C and Rust runtimes side by side. This process caught an unhandled LZW decompressor edge case and an out-of-bounds write bug that had been introduced by an earlier patch to the original C source. Teams validating language migrations with differential fuzzing can track approaches like this on daily.dev."}},{"@type":"Question","name":"Did rewriting giflib in Rust protect against CVE-2026-26740 before it was disclosed?","acceptedAnswer":{"@type":"Answer","text":"Yes, production nodes running Google's Rust replacement of giflib were structurally immune to the heap out-of-bounds write vulnerability cataloged as CVE-2026-26740, which an external researcher found in the upstream C library, before the CVE was publicly disclosed. This let Google also remove legacy OS-level sandboxing previously needed to isolate image decoding, improving p99 tail latency. Developers tracking memory-safety CVEs and Rust migrations can follow the details on daily.dev."}}]} ```