--- title: I want extern "fil-c" | daily.dev description: An argument for building a Rust FFI that speaks Fil-C's ABI, letting legacy C code run under Fil-C's memory-safe runtime (capabilities, checked pointers,... canonical: https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: I want extern "fil-c" | daily.dev og:description: An argument for building a Rust FFI that speaks Fil-C's ABI, letting legacy C code run under Fil-C's memory-safe runtime (capabilities, checked pointers,... og:url: https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl og:image: https://api.daily.dev/og/posts/jbh9JxDwL.png og:image:alt: I want extern "fil-c" 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. # I want extern "fil-c" **[Lobsters](https://daily.dev/sources/lobsters)** · 4 min read · 0 upvotes · 0 comments ## Summary An argument for building a Rust FFI that speaks Fil-C's ABI, letting legacy C code run under Fil-C's memory-safe runtime (capabilities, checked pointers, garbage collection) while Rust handles compile-time-safe hot paths. The author proposes a narrow first version (scalar values, copied strings/slices, opaque handles) with no unsafe escape hatch, points to filnix (a Nix cross-compilation platform packaging Fil-C with over 100 nixpkgs ports) as existing groundwork, and notes Zig's Andrew Kelley has proposed a similar fil ABI for Zig's own C/C++ interop. The piece ends with an invitation to collaborate on this at the OceanSprint event in Lanzarote. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is Fil-C and how does it make C memory-safe? Fil-C is a recompiler for C and C++ that adds capabilities, runtime pointer checks, and a concurrent garbage collector, turning memory-safety violations into panics instead of exploits. It is source-compatible with standard C but intentionally not ABI-compatible, meaning it requires the whole program and its dependencies to use the Fil-C ABI rather than mixing with ordinary unsafe C. _Track emerging memory-safety tooling like Fil-C as it evolves by following related coverage on daily.dev._ ### Is there a way to call Fil-C compiled C code safely from Rust? Not yet, but it has been proposed. Rust's ordinary extern "C" speaks the ABI Fil-C calls Yolo-C, so a real bridge would need Rust, Fil-C, or generated stubs to exchange values without breaking Fil-C's whole-program safety guarantee. A first version could stay narrow, supporting only scalar values, copied strings and slices, and opaque handles with no unsafe escape hatch back to plain C. _Developers weighing Rust FFI safety trade-offs can follow how this bridge proposal develops on daily.dev._ ### What is filnix and how does it relate to Fil-C? filnix is a Nix cross-compilation platform, built by Mikael Brockman, that packages Fil-C and provides ports for more than 100 nixpkgs packages. It rebuilds the transitive dependency closure specifically for the Fil-C ABI instead of accidentally linking ordinary C into it, giving the ecosystem a reproducible toolchain and test bed for building a future Rust-Fil-C bridge. _Anyone evaluating Nix-based cross-compilation for memory-safe C can keep up with filnix progress via daily.dev._ ## Similar posts on daily.dev - [Memory Safety Absolutists](https://daily.dev/posts/memory-safety-absolutists-sufigv3zl) · Hacker News · 1 upvotes · 0 comments --- Tags: [#rust](https://daily.dev/tags/rust), [#zig](https://daily.dev/tags/zig) [View this post on daily.dev](https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl) ```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":"I want extern \"fil-c\"","url":"https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl"},"datePublished":"2026-08-13T20:40:42.448Z","dateModified":"2026-08-13T20:56:32.802Z","description":"An argument for building a Rust FFI that speaks Fil-C's ABI, letting legacy C code run under Fil-C's memory-safe runtime (capabilities, checked pointers,...","image":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","thumbnailUrl":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","isAccessibleForFree":true,"articleSection":"Lobsters","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":"Lobsters","logo":"https://media.daily.dev/image/upload/s--tl8v_Fku--/f_auto,t_logo/v1698841318/logos/lobste.jpg","url":"https://daily.dev/sources/lobsters"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"rust,zig","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Lobsters","item":"https://daily.dev/sources/lobsters"},{"@type":"ListItem","position":3,"name":"I want extern \"fil-c\""}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/i-want-extern-fil-c--jbh9jxdwl#faq","mainEntity":[{"@type":"Question","name":"What is Fil-C and how does it make C memory-safe?","acceptedAnswer":{"@type":"Answer","text":"Fil-C is a recompiler for C and C++ that adds capabilities, runtime pointer checks, and a concurrent garbage collector, turning memory-safety violations into panics instead of exploits. 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