--- title: Stackless Coroutines in Libdex | daily.dev description: Christian Hergert introduces stackless coroutines as a new lightweight alternative to fibers in Libdex, a C async/futures library used in GNOME. Unlike fibers,... canonical: https://daily.dev/posts/stackless-coroutines-in-libdex-9vniovnm6 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Stackless Coroutines in Libdex | daily.dev og:description: Christian Hergert introduces stackless coroutines as a new lightweight alternative to fibers in Libdex, a C async/futures library used in GNOME. Unlike fibers,... og:url: https://daily.dev/posts/stackless-coroutines-in-libdex-9vniovnm6 og:image: https://api.daily.dev/og/posts/9VniovNM6.png og:image:alt: Stackless Coroutines in Libdex 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. # Stackless Coroutines in Libdex **[Happenings in GNOME](https://daily.dev/sources/chergert)** · 3 min read · 0 upvotes · 0 comments ## Summary Christian Hergert introduces stackless coroutines as a new lightweight alternative to fibers in Libdex, a C async/futures library used in GNOME. Unlike fibers, stackless coroutines don't require a separate stack or register saving, making them cheaper for simple future-coordinating work, though benchmarks show only modestly lower overhead than fibers. They integrate with DexFuture and DexTaskGroup, support cancellation, and use switch/case-based suspension (via DEX_COROUTINE_SUSPEND_* macros) to stay portable across compilers lacking address-of-label support, like MSVC and clang-cl. State must be kept in closure structs rather than on the stack, and helper macros like DEX_DEFINE_CLOSURE_TYPE simplify creating the needed boilerplate. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What are stackless coroutines in Libdex and how do they differ from fibers? Stackless coroutines are a new lightweight concurrency primitive added to Libdex that avoid the need for a separate stack or register saving, unlike fibers. They suspend and resume by re-entering the function and jumping to the next position via switch/case, reusing the calling thread's stack, with state saved in a closure struct instead. They can still be represented as a DexFuture and composed with fibers and threadpool work inside a DexTaskGroup, and benchmarks show somewhat lower overhead than fibers. _Following async C patterns like Libdex's stackless coroutines is easier with daily.dev's developer feed._ ### Why can't Libdex stackless coroutines use the same await syntax as fibers? Stackless coroutines rely on switch/case jumps rather than direct stack manipulation to remain portable across Linux, Windows, FreeBSD, Solaris, and macOS, particularly because MSVC and clang-cl lack address-of-label support. This forces a different, more explicit suspend/resume syntax using DEX_COROUTINE_SUSPEND_* macros instead of the syntax fibers use for awaiting futures. _Developers weighing portability tradeoffs in async C libraries can track changes like this via daily.dev._ ### How do I define closure state for a Libdex stackless coroutine? Use the DEX_DEFINE_CLOSURE_TYPE() macro, which generates the typedef struct along with matching _new() and _free() helper functions in one expansion. Fields are declared with helpers like DEX_DEFINE_CLOSURE_VALUE for plain values, DEX_DEFINE_CLOSURE_POINTER for pointers with a custom free function, and DEX_DEFINE_CLOSURE_OBJECT for GObject-based types, ensuring state survives across suspend points since it can't live on the stack. _daily.dev helps C developers keep up with library-specific patterns like Libdex's closure macros._ ## Similar posts on daily.dev - [vittorio romeo's website](https://daily.dev/posts/vittorio-romeo-s-website-eqgqgk7vc) · Lobsters · 0 upvotes · 0 comments --- Tags: [#linux](https://daily.dev/tags/linux), [#c](https://daily.dev/tags/c) [View this post on daily.dev](https://daily.dev/posts/stackless-coroutines-in-libdex-9vniovnm6) ```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":"Stackless Coroutines in Libdex","url":"https://daily.dev/posts/stackless-coroutines-in-libdex-9vniovnm6","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/stackless-coroutines-in-libdex-9vniovnm6"},"datePublished":"2026-08-31T05:54:44.258Z","dateModified":"2026-08-31T05:56:34.616Z","description":"Christian Hergert introduces stackless coroutines as a new lightweight alternative to fibers in Libdex, a C async/futures library used in GNOME. 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