CTASSERT(9)

💅 CTASSERT(9) — ok bestie, let's talk compile-time drama

So this is a page from the Kernel Developer's Manual — yes, kernel devs have manuals, and yes, they're iconic. Today's main character is CTASSERT, the compile time assertion macro. Buckle up 🎀

✨ NAME ✨

CTASSERT — the compile time assertion macro, periodt.

🌸 SYNOPSIS 🌸

#include <sys/param.h>
#include <sys/systm.h>

CTASSERT(expression);

That's it. Two headers and a vibe. 🦋

💖 DESCRIPTION 💖

Okay so first thing first, and I need you to hear me on this one: the CTASSERT() macro is deprecated. Like, it still works, but it's giving "my older cousin's MySpace". The C11 standard's _Static_assert() is the one you should be using instead, fr fr.

And if you're on a compiler that predates C11? Don't panic, bestie 🫶 — you should include the sys/cdefs.h header, because that's the one that provides compatibility for pre-C11 compilers. Cute of them honestly.

Now for what it actually does: the CTASSERT() macro evaluates expression at compile time, and if that expression is false, it causes a compiler error. No runtime surprises, no "oops we found out at 3am" — the compiler just tells you straight up. It's giving honest queen energy. 👑

And why would you want that? Because CTASSERT() is useful for asserting the size or alignment of important data structures and variables during compilation — stuff that would otherwise cause the code to fail at run time. Which is so much worse. Run time failures are the worst kind of plot twist. 💀

🔥 EXAMPLES 🔥

Say you wanna assert that the size of the uuid structure is 16 bytes. You write:

CTASSERT(sizeof(struct uuid) == 16);

And the compiler either agrees with you or it does not. No in-between. No cap. ✨

🌈 SEE ALSO 🌈

• KASSERT(9) — the runtime sibling, go say hi 👋

👑 AUTHORS 👑

This manual page was written by Hiten M. Pandya <hmp@FreeBSD.org>. We love a credited author. 🎀

And that's the whole page, bestie! This little gem came to you from Debian, dated August 1, 2015 — so yeah, it's been slaying since 2015. Go assert something at compile time, your future self at 3am will thank you. Mwah 💅💖✨