--- title: Zig: a great fit for emulators - Benjamin Feng | daily.dev description: A developer shares their experience building a Game Boy emulator called 'fun dude' in Zig, compiled to WebAssembly. The talk covers three key areas where Zig... canonical: https://daily.dev/posts/zig-a-great-fit-for-emulators---benjamin-feng-7fjq6rokb twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Zig: a great fit for emulators - Benjamin Feng | daily.dev og:description: A developer shares their experience building a Game Boy emulator called 'fun dude' in Zig, compiled to WebAssembly. The talk covers three key areas where Zig... og:url: https://daily.dev/posts/zig-a-great-fit-for-emulators---benjamin-feng-7fjq6rokb og:image: https://api.daily.dev/og/posts/7fjQ6ROkb.png og:image:alt: Zig: a great fit for emulators - Benjamin Feng 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. # Zig: a great fit for emulators - Benjamin Feng **[Lobsters](https://daily.dev/sources/lobsters)** · 34 min read · 3 upvotes · 0 comments ## Summary A developer shares their experience building a Game Boy emulator called 'fun dude' in Zig, compiled to WebAssembly. The talk covers three key areas where Zig outperforms C for emulator development: explicit casting that eliminates undefined behavior, built-in compiler intrinsics like CTZ that improved interrupt handling performance from 15-20% CPU usage to a single branch, and enum arrays that prevent accidental register cross-contamination. The speaker also discusses challenges with Zig's immaturity, packed struct bugs in WebAssembly, and the freestanding standard library that simplified the WebAssembly port. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How does Zig's ctz compiler intrinsic improve performance over a branching C implementation for interrupt handling? Using the ctz (count trailing zeros) intrinsic in Zig to detect the active interrupt bit replaced a five-branch, two-to-three-instruction-each C implementation with a single branch taking around four cycles. The original C version consumed roughly 15-20 percent of CPU cycles in the emulator's interrupt handling, since C exposes such intrinsics only through the compiler rather than the language itself, making them harder to discover. _Anyone optimizing low-level emulator code can compare notes on compiler intrinsics and performance tuning through daily.dev._ ### What is the biggest known bug when using packed structs in Zig for WebAssembly targets? Packed structs in Zig have padding bugs when a type crosses a byte boundary, particularly noticeable when targeting WebAssembly. Fields under one byte work fine, but crossing natural word boundaries causes unexpected padding up to four bytes, which the compiler handles poorly. It is a known compiler bug rather than a design flaw, and many in the Zig community recommend avoiding packed structs because of it. _Developers debugging Zig WebAssembly builds can track known compiler quirks like this one via daily.dev._ ### What are the main challenges of compiling a Zig program to WebAssembly? Compiling Zig to WebAssembly requires manually creating wrapper export functions because Zig has no stable ABI, and types like slices don't exist outside Zig so they must be converted to raw pointers. The build must target wasm32-freestanding, avoid any operating-system-based standard library calls such as debug warn or standard output, and only use the WebAssembly-native types i32, i64, f32, and f64 across the boundary. _Teams evaluating Zig for WebAssembly targets can weigh these ABI and tooling trade-offs on daily.dev._ ## Similar posts on daily.dev - [ZigCool](https://daily.dev/posts/zigcool-w6vkx2tr6) · Hacker News · 4 upvotes · 0 comments - [Functional Programmers need to take a look at Zig.](https://daily.dev/posts/functional-programmers-need-to-take-a-look-at-zig--rz9pafogz) · Lobsters · 10 upvotes · 1 comments --- Tags: [#webassembly](https://daily.dev/tags/webassembly), [#zig](https://daily.dev/tags/zig) [View this post on daily.dev](https://daily.dev/posts/zig-a-great-fit-for-emulators---benjamin-feng-7fjq6rokb) ```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":"Zig: a great fit for emulators - Benjamin Feng","url":"https://daily.dev/posts/zig-a-great-fit-for-emulators---benjamin-feng-7fjq6rokb","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/zig-a-great-fit-for-emulators---benjamin-feng-7fjq6rokb"},"datePublished":"2026-08-11T05:02:31.873Z","dateModified":"2026-09-14T06:04:39.483Z","description":"A developer shares their experience building a Game Boy emulator called 'fun dude' in Zig, compiled to WebAssembly. 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