STDC_LEADING_ONES(3)

🎀 STDC_LEADING_ONES(3) 🎀

Library Functions Manual? More like library functions bestie manual 💖 okay so welcome to the group chat, we're learning how to count leading ones and it's lowkey iconic.

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🌸 NAME 🌸

stdc_leading_ones — find the number of leading ones in an integer 💅

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✨ SYNOPSIS ✨

Link the Standard C Library: Standard C Library (libc, -lc). Header first, bestie: #include <stdbit.h>.

unsigned int
stdc_leading_ones_uc(unsigned char value);

unsigned int
stdc_leading_ones_us(unsigned short value);

unsigned int
stdc_leading_ones_ui(unsigned int value);

unsigned int
stdc_leading_ones_ul(unsigned long value);

unsigned int
stdc_leading_ones_ull(unsigned long long value);

unsigned int
stdc_leading_ones(value);

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🦋 DESCRIPTION 🦋

Okay so the stdc_leading_ones_type() family of functions returns the number of leading ones in value ✨. Here value is of type unsigned char, unsigned short, unsigned int, unsigned long, or unsigned long long, and type is uc, us, ui, ul, or ull respectively 💅.

The stdc_leading_ones(value) type-generic macro is the main character here: it picks the appropriate stdc_leading_ones_type() function based on the type of value 🫶. No cap, it just knows.

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💖 RETURN VALUES 💖

Returns the number of leading ones in value. If value is all ones, the total number of bits in the type of value is returned 🔥. So bestie, if it's literally all 1s, you get the whole bit-width back.

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🌈 SEE ALSO 🌈

• stdbit(3)
• stdc_leading_zeros(3)
• stdc_trailing_ones(3)
• stdc_first_leading_zero(3)

Go sip on those too, they're all in the same friend group 💜

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⭐ STANDARDS ⭐

The stdc_leading_ones_type() family of functions and the stdc_leading_ones() type-generic macro conform to . 💀 (That's what the page says, don't come for me.)

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🍓 HISTORY 🍓

The stdc_leading_ones_type() family of functions and the stdc_leading_ones() type-generic macro were added in FreeBSD 15.1 ✨ periodt.

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👑 AUTHOR 👑

Robert Clausecker <fuz@FreeBSD.org> 🫶

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💖 Source/version: Debian — date: November 9, 2025 💖