size_sub(9)

📦 version 7.3.1, in nixpkgs unstable

💅 size_sub(9) 💅

okay so bestie, welcome to the Kernel API Manual entry for size_sub — yes, we're doing kernel math today, and no, it's not scary, i promise. this whole page is literally just "subtract two numbers but don't let it wrap around and ruin your life." iconic behaviour, honestly ✨

🎀 NAME 🎀

size_sub — Calculate size_t subtraction with saturation at SIZE_MAX.

like, it's a subtraction, but make it safe. 💖

🦋 SYNOPSIS 🦋

size_t size_sub (size_t minuend , size_t subtrahend );

that's it. two arguments, one size_t back. clean, tiny, slays. 💅

🌸 ARGUMENTS 🌸

  • minuend — the value you're subtracting from. the main character of this operation, lowkey. 👑
  • subtrahend — the value you're subtracting from minuend. the one doing the taking. 😭

⭐ RETURN ⭐

so it calculates minuend - subtrahend, with both of them promoted to size_t, and if there's any overflow the return value just becomes SIZE_MAX. no cap, it saturates. 🫶

and here's the important bit, bestie, listen up 👂 — for composition with the size_add and size_mul helpers, neither argument may be SIZE_MAX (or the result will be forced to SIZE_MAX). fr fr, don't do it. 💀

also: the lvalue must be size_t to avoid implicit type conversion. like, keep your types honest, okay? the vibe check on your variable types matters. 🌈

🔥 SEE ALSO 🔥

Kernel file ./include/linux/overflow.h — and the whole overflow bestie squad:

like, that's a whole friend group and they all ate. 🍓🧚

ngl, if you're doing subtraction on sizes in the kernel without checking overflow, this page is your sign from the universe to stop. 💜

and that's the whole page, bestie!! 🎀 this one lives in ./include/linux and it's dated October 2026 — so like, whenever you're reading this, it's giving timeless. mwah, go forth and subtract safely. 💖🦋✨

📦 where this page comes from