MB_LEN_MAX(3)

💅 MB_LEN_MAX(3) — Library Functions Manual ✨

okay bestie come closer 🫶 we're doing a man page and honestly this one is short but iconic. it lives in section 3 of the manual (library functions, if you didn't know — iykyk) and it's giving "small macro, big feelings."

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🌸 NAME 🌸

MB_LEN_MAX — the maximum multibyte length of a character across all locales 🦋

📚 LIBRARY 📚

the Standard C library (that's **libc for the girlies keeping track) 💜

✨ SYNOPSIS ✨

#include <limits.h>

that's it. that's the whole thing. no function call, no args, nothing to mess up. we love a low-maintenance macro 💅

🎀 DESCRIPTION 🎀

okay so MB_LEN_MAX is a macro, right, and it holds the maximum number of bytes you'd ever need to represent a single wide character — and not just in your locale, bestie, in ANY of the supported locales 🌈

like… it's the worst-case-scenario number. the "pack an extra outfit just in case" number. the "we don't know where we're going so let's be ready for anything" number 🧚

🔥 RETURN VALUE 🔥

a constant integer that is greater than zero ⭐ (yes, literally just a number, and yes, it's always positive, no sad zero vibes here)

👑 STANDARDS 👑

C11, POSIX.1-2008. it's certified, it's legit 👑

🕰️ HISTORY 🕰️

C99, POSIX.1-2001. so it's been around a minute, lowkey a classic, highkey a legend 🎀

💀 NOTES 💀

okay this is the part where people get it WRONG, so listen up bestie 🫶

MB_LEN_MAX and sizeof(wchar_t) are totally unrelated. like, not cousins, not mutuals, not even in the same group chat. do NOT conflate them. 💀

and for the numbers girlies, in glibc:

• MB_LEN_MAX is typically 16 (but 6 in glibc versions earlier than 2.2 — throwback era, don't ask)
• sizeof(wchar_t) is 4

see? different. periodt. 💅

🦋 SEE ALSO 🦋

• MB_CUR_MAX(3) — the other multibyte bestie, go say hi 🫶

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and that's the whole page, bestie 💖 stay multibyte-aware out there ✨

this lil rewrite is based on Linux man-pages 6.20, dated 2026-02-08 🎀 — with love, from your favorite Unix girly 💅