STDBIT(3)

🌸 NAME 🌸

stdbit(3) — bit and byte utilities. This is the Library Functions Manual entry for the <stdbit.h> bit/byte utility crew. 💅

✨ SYNOPSIS ✨

Okay bestie, the standard C library is libc — link it with -lc — and the header is <stdbit.h>. Here’s the synopsis in all its glory:

Standard C Library (libc, -lc) #include <stdbit.h>
#define __STDC_ENDIAN_LITTLE__
#define __STDC_ENDIAN_BIG__
#define __STDC_ENDIAN_NATIVE__

unsigned int
stdc_count_leading_zeros(value);

unsigned int
stdc_count_leading_ones(value);

unsigned int
stdc_count_trailing_zeros(value);

unsigned int
stdc_count_trailing_ones(value);

unsigned int
stdc_first_leading_zero(value);

unsigned int
stdc_first_leading_one(value);

unsigned int
stdc_first_trailing_zero(value);

unsigned int
stdc_first_trailing_one(value);

unsigned int
stdc_count_zeros(value);

unsigned int
stdc_count_ones(value);

bool
stdc_has_single_bit(value);

unsigned int
stdc_bit_width(value);

typeof(value)
stdc_bit_floor(value);

typeof(value)
stdc_bit_ceil(value);

That’s the whole function lineup, no cap. 🎀

💖 DESCRIPTION 💖

First up: endianness. The __STDC_ENDIAN_NATIVE__ macro describes the byte order — or endianness — of the machine for which the program is built. If the machine has big-endian byte order, this macro is equal to __STDC_ENDIAN_BIG__. If the machine has little-endian byte order, this macro is equal to __STDC_ENDIAN_LITTLE__. Otherwise, the macro has a value that is equal to neither. That’s the whole endianness tea. 🌈

The bit and byte utility functions analyze the bits within a datum. Each function func is provided in five variants stdc_func_type(value), where value is of type unsigned char, unsigned short, unsigned int, unsigned long, or unsigned long long for type being uc, us, ui, ul, or ull respectively. So yes, there’s a flavor for every unsigned width, and the suffixes are literally right there. 💅

Additionally, for each func, a type-generic macro stdc_func(value) is provided. It picks the appropriate function stdc_func_type(value) based on the type of value. It’s giving “the macro knows which one you meant” energy. 🦋

🎀 SEE ALSO 🎀

Go read these too, iykyk:

• arch(7)
• bitstring(3)
• ffs(3)
• fls(3)
• stdc_count_leading_zeros(3)
• stdc_count_leading_ones(3)
• stdc_count_trailing_zeros(3)
• stdc_count_trailing_ones(3)
• stdc_first_leading_zero(3)
• stdc_first_leading_one(3)
• stdc_first_trailing_zero(3)
• stdc_first_trailing_one(3)
• stdc_count_zeros(3)
• stdc_count_ones(3)
• stdc_has_single_bit(3)
• stdc_bit_width(3)
• stdc_bit_floor(3)
• stdc_bit_ceil(3)

⭐ STANDARDS ⭐

The macros and functions of the <stdbit.h> header conform to . Yes, bestie, the source sentence really does end there — no standard name is listed. 😭

🦋 HISTORY 🦋

The <stdbit.h> header and the macros and functions defined therein were added in FreeBSD 15.1. Periodt. 🔥

👑 AUTHOR 👑

Robert Clausecker <fuz@FreeBSD.org>. Show some love. 🫶

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💖 Cute sign-off: this page is from Debian, dated November 9, 2025, and the manual is STDBIT(3). Bye bestie, go count some bits! 🎀