--- title: Memory Safety’s Hardest Problem | daily.dev description: A brief but pointed analysis of memory safety's hardest unsolved problem: type confusion via tagged unions. When a union is initialized as one type, a pointer... canonical: https://daily.dev/posts/memory-safety-s-hardest-problem-ob8qh0lmc twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Memory Safety’s Hardest Problem | daily.dev og:description: A brief but pointed analysis of memory safety's hardest unsolved problem: type confusion via tagged unions. When a union is initialized as one type, a pointer... og:url: https://daily.dev/posts/memory-safety-s-hardest-problem-ob8qh0lmc og:image: https://api.daily.dev/og/posts/Ob8Qh0lMC.png og:image:alt: Memory Safety’s Hardest Problem og:image:width: 1200 og:image:height: 630 og:locale: en --- [matklad](https://daily.dev/sources/matklad) [Read post](https://api.daily.dev/r/Ob8Qh0lMC) # [Memory Safety’s Hardest Problem](https://api.daily.dev/r/Ob8Qh0lMC "Go to post") A brief but pointed analysis of memory safety's hardest unsolved problem: type confusion via tagged unions. When a union is initialized as one type, a pointer taken to its internals, then overwritten with a different type, the pointer becomes dangerously mistyped. This issue breaks even Ada's safety guarantees. The post also argues that buffer overflows — the most exploitable memory error in practice — are trivially fixable with bounds checks, and laments that the industry missed Walter Bright's early insight about array syntax in C that could have prevented many vulnerabilities. [#rust](/tags/rust "Check all #rust posts") Jul 20•1m read time•From [matklad.github.io](https://api.daily.dev/r/Ob8Qh0lMC "matklad.github.io") [](https://api.daily.dev/r/Ob8Qh0lMC "Go to post") 10.4K Impressions5 Upvotes1 Comment Comment Bookmark Copy Share your thoughtsPost [](https://daily.dev/sources/matklad) [matklad](https://daily.dev/sources/matklad "https://daily.dev/sources/matklad") Matthias Noback's expertise in PHP and domain-driven design (DDD) offers readers insights into buil... Read more 33 Followers • 474 Upvotes #### Would you recommend this post? Copy link WhatsApp Facebook X New Squad Copy linkShare with your friends 5 1 ```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":"Memory Safety’s Hardest Problem","url":"https://daily.dev/posts/memory-safety-s-hardest-problem-ob8qh0lmc","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/memory-safety-s-hardest-problem-ob8qh0lmc"},"datePublished":"2026-07-20T13:21:06.128Z","dateModified":"2026-07-20T18:21:37.223Z","description":"A brief but pointed analysis of memory safety's hardest unsolved problem: type confusion via tagged unions. When a union is initialized as one type, a pointer...","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":"matklad","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":"matklad","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/c34dbbf360354a179786e8a127718b12","url":"https://daily.dev/sources/matklad"},"commentCount":1,"discussionUrl":"https://daily.dev/posts/memory-safety-s-hardest-problem-ob8qh0lmc","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":5},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":1}],"keywords":"rust","timeRequired":"PT1M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"matklad","item":"https://daily.dev/sources/matklad"},{"@type":"ListItem","position":3,"name":"Memory Safety’s Hardest Problem"}]} {"@context":"https://schema.org","@type":"WebPage","@id":"https://daily.dev/posts/memory-safety-s-hardest-problem-ob8qh0lmc","comment":[{"@type":"Comment","text":"The example code is zig and they mention C but there is nothing here about rust (which is fine) but the tags should probably be updated so it gets in front of the correct audience. Fortunately, I follow both Rust and Zig but this should probably be rectified.","datePublished":"2026-07-20T17:34:30.723Z","url":"https://daily.dev/posts/Ob8Qh0lMC#c-Qta3Bwk3M","author":{"@type":"Person","name":"Kahlil Wallace","url":"https://daily.dev/khauma","image":"https://media.daily.dev/image/upload/s--QvppE9Ip--/f_auto/v1767378558/avatars/avatar_7eQFeSQRDx0muV3n92gxT?_a=BAMAK+ZW0"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":3}}]} ```