--- title: In one of your older codebases, did a Linked List ever... description: A team built a custom undo stack using a doubly linked list. A subtle pointer assignment bug during merge operations caused silent state corruption that only... canonical: https://daily.dev/posts/in-one-of-your-older-codebases-did-a-linked-list-ever-hide-a-bug-that-took-weeks-to-surface--rp9as5pdd twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: In one of your older codebases, did a Linked List ever hide a bug that took weeks to surface? | daily.dev og:description: A team built a custom undo stack using a doubly linked list. A subtle pointer assignment bug during merge operations caused silent state corruption that only... og:url: https://daily.dev/posts/in-one-of-your-older-codebases-did-a-linked-list-ever-hide-a-bug-that-took-weeks-to-surface--rp9as5pdd og:image: https://api.daily.dev/og/posts/rP9as5PdD.png og:image:alt: In one of your older codebases, did a Linked List ever hide a bug that took weeks to surface? 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. # In one of your older codebases, did a Linked List ever hide a bug that took weeks to surface? **[Rebeloper](https://daily.dev/sources/rebeloper)** · 1 min read · 0 upvotes · 0 comments ## Summary A team built a custom undo stack using a doubly linked list. A subtle pointer assignment bug during merge operations caused silent state corruption that only surfaced weeks later when users hit deep undo paths. The fix was replacing the clever custom structure with a simpler value snapshot using copy-on-write semantics. ## Full article daily.dev links to this article rather than hosting it. 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