--- title: Pointer Provenance— The Hidden Identity of Every C Pointer description: Explains pointer provenance in C — the compiler's abstract notion of which object a pointer legitimately belongs to, distinct from its raw numeric address.... canonical: https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Pointer Provenance— The Hidden Identity of Every C Pointer | daily.dev og:description: Explains pointer provenance in C — the compiler's abstract notion of which object a pointer legitimately belongs to, distinct from its raw numeric address.... og:url: https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub og:image: https://api.daily.dev/og/posts/MaDpNagUb.png og:image:alt: Pointer Provenance— The Hidden Identity of Every C Pointer 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. # Pointer Provenance— The Hidden Identity of Every C Pointer **[Towards Dev](https://daily.dev/sources/towardsdev)** · 11 min read · 0 upvotes · 0 comments ## Summary Explains pointer provenance in C — the compiler's abstract notion of which object a pointer legitimately belongs to, distinct from its raw numeric address. Covers why aliasing rules exist, how casting through uintptr_t or memcpy typically preserves provenance, why pointer subtraction across unrelated objects is undefined behavior, how strict aliasing relates to provenance, and how these rules let compilers eliminate redundant memory loads for faster code. Ends by teasing a follow-up on std::launder. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why does casting two pointers to integers and comparing them equal not make dereferencing one of them safe in C? Equal integer addresses do not grant equal provenance. Even if a pointer p is mathematically computed to match the address of a separate object y, the compiler's abstract machine still treats p as belonging strictly to its original object x, so dereferencing p to access y is undefined behavior despite the addresses being numerically identical. _Developers reasoning through subtle C undefined behavior cases can find grounded explainers like this via daily.dev._ ### Does subtracting two pointers in C always produce a well-defined result? No, pointer subtraction is only well-defined when both pointers point into the same array object; otherwise the subtraction itself is undefined behavior regardless of provenance. When valid, the resulting integer carries an 'empty' provenance and is treated as a plain offset number with no ownership tied to any object. _Anyone tracking these tricky C pointer arithmetic rules can keep sharpening that knowledge through daily.dev._ ### How does strict aliasing differ from pointer provenance in C compiler optimizations? Strict aliasing and provenance are sibling rules: provenance tracks which object a pointer's memory came from, while strict aliasing tracks what type the memory is treated as. Under strict aliasing, a compiler can assume an int* and a float* never point to the same object even if their addresses match, letting it optimize away reloads just as provenance does for same-typed pointers to distinct objects. _Developers untangling C aliasing rules for performance-sensitive code can dig deeper via daily.dev._ ## Similar posts on daily.dev - [Who Owns the Memory? Part 1: What is an Object?](https://daily.dev/posts/who-owns-the-memory-part-1-what-is-an-object--gsfcmwo0k) · Lobsters · 0 upvotes · 0 comments - [Aliasing — Matt Godbolt’s blog](https://daily.dev/posts/aliasing-matt-godbolt-s-blog-rybl5kv9b) · Hacker News · 1 upvotes · 0 comments - [Defining Model Provenance: A Constitution for AI Supply Chain Safety and Security](https://daily.dev/posts/defining-model-provenance-a-constitution-for-ai-supply-chain-safety-and-security-84snszxv2) · Cisco · 0 upvotes · 0 comments --- Tags: [#c](https://daily.dev/tags/c), [#compiler-optimization](https://daily.dev/tags/compiler-optimization) [View this post on daily.dev](https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub) ```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":"Pointer Provenance— The Hidden Identity of Every C Pointer","url":"https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub"},"datePublished":"2026-08-21T06:48:11.650Z","dateModified":"2026-09-13T19:08:28.111Z","description":"Explains pointer provenance in C — the compiler's abstract notion of which object a pointer legitimately belongs to, distinct from its raw numeric address....","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/c37577dfd1186016b578a083ec1e4df2?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/c37577dfd1186016b578a083ec1e4df2?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Towards Dev","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":"Towards Dev","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/2c710db2750a4a70835862534cb7c9d4","url":"https://daily.dev/sources/towardsdev"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"c,compiler-optimization","timeRequired":"PT11M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Towards Dev","item":"https://daily.dev/sources/towardsdev"},{"@type":"ListItem","position":3,"name":"Pointer Provenance— The Hidden Identity of Every C Pointer"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/pointer-provenance-the-hidden-identity-of-every-c-pointer-madpnagub#faq","mainEntity":[{"@type":"Question","name":"Why does casting two pointers to integers and comparing them equal not make dereferencing one of them safe in C?","acceptedAnswer":{"@type":"Answer","text":"Equal integer addresses do not grant equal provenance. Even if a pointer p is mathematically computed to match the address of a separate object y, the compiler's abstract machine still treats p as belonging strictly to its original object x, so dereferencing p to access y is undefined behavior despite the addresses being numerically identical. Developers reasoning through subtle C undefined behavior cases can find grounded explainers like this via daily.dev."}},{"@type":"Question","name":"Does subtracting two pointers in C always produce a well-defined result?","acceptedAnswer":{"@type":"Answer","text":"No, pointer subtraction is only well-defined when both pointers point into the same array object; otherwise the subtraction itself is undefined behavior regardless of provenance. When valid, the resulting integer carries an 'empty' provenance and is treated as a plain offset number with no ownership tied to any object. Anyone tracking these tricky C pointer arithmetic rules can keep sharpening that knowledge through daily.dev."}},{"@type":"Question","name":"How does strict aliasing differ from pointer provenance in C compiler optimizations?","acceptedAnswer":{"@type":"Answer","text":"Strict aliasing and provenance are sibling rules: provenance tracks which object a pointer's memory came from, while strict aliasing tracks what type the memory is treated as. Under strict aliasing, a compiler can assume an int* and a float* never point to the same object even if their addresses match, letting it optimize away reloads just as provenance does for same-typed pointers to distinct objects. Developers untangling C aliasing rules for performance-sensitive code can dig deeper via daily.dev."}}]} ```