libc/stdbit: add man pages for stdbit functions

This adds man pages for each group of functions in <stdbit.h>.
The man pages have cross references to one-another.
Cross references from external man pages to these will be added
in a later commit.

Reviewed by:	pauamma@gundo.com, kib
Approved by:	markj (mentor)
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D53659

15 files changed, 1283 insertions, 0 deletions

diff --git a/lib/libc/stdbit/Makefile.inc b/lib/libc/stdbit/Makefile.inc
index 2ea96d2b6dfe..fceccb12b589 100644
--- a/lib/libc/stdbit/Makefile.inc
+++ b/lib/libc/stdbit/Makefile.inc
@@ -17,3 +17,18 @@ SRCS+=	stdc_bit_ceil.c \
 	stdc_trailing_zeros.c
 
 SYM_MAPS+=${LIBC_SRCTOP}/stdbit/Symbol.map
+
+MAN+=	stdc_bit_ceil.3 \
+	stdc_bit_floor.3 \
+	stdc_bit_width.3 \
+	stdc_count_ones.3 \
+	stdc_count_zeros.3 \
+	stdc_first_leading_one.3 \
+	stdc_first_leading_zero.3 \
+	stdc_first_trailing_one.3 \
+	stdc_first_trailing_zero.3 \
+	stdc_has_single_bit.3 \
+	stdc_leading_ones.3 \
+	stdc_leading_zeros.3 \
+	stdc_trailing_ones.3 \
+	stdc_trailing_zeros.3
diff --git a/lib/libc/stdbit/stdc_bit_ceil.3 b/lib/libc/stdbit/stdc_bit_ceil.3
new file mode 100644
index 000000000000..470b255f471e
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_ceil.3
@@ -0,0 +1,81 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_BIT_CEIL 3
+.Os
+.Sh NAME
+.Nm stdc_bit_ceil
+.Nd round up to the next power of\~2
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned char
+.Fn stdc_bit_ceil_uc "unsigned char value"
+.Ft unsigned short
+.Fn stdc_bit_ceil_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_bit_ceil_ui "unsigned int value"
+.Ft unsigned long
+.Fn stdc_bit_ceil_ul "unsigned long value"
+.Ft unsigned long long
+.Fn stdc_bit_ceil_ull "unsigned long long value"
+.Ft typeof Ns Pq Em value
+.Fn stdc_bit_ceil "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_bit_ceil_ Ns Em type Ns ()
+family of functions rounds
+.Fa value
+up to the next power of\~2, where
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_bit_ceil "value"
+type-generic macro picks the appropriate
+.Nm stdc_bit_ceil_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns
+.Fa value
+round up to the next power of\~2.
+If this value is not representable,
+0\~is returned.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_bit_floor 3
+.Sh STANDARDS
+The
+.Nm stdc_bit_ceil_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_bit_ceil
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_bit_ceil_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_bit_ceil
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_bit_floor.3 b/lib/libc/stdbit/stdc_bit_floor.3
new file mode 100644
index 000000000000..3e90c34f070f
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_floor.3
@@ -0,0 +1,83 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_BIT_FLOOR 3
+.Os
+.Sh NAME
+.Nm stdc_bit_floor
+.Nd round down to the previous power of\~2
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned char
+.Fn stdc_bit_floor_uc "unsigned char value"
+.Ft unsigned short
+.Fn stdc_bit_floor_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_bit_floor_ui "unsigned int value"
+.Ft unsigned long
+.Fn stdc_bit_floor_ul "unsigned long value"
+.Ft unsigned long long
+.Fn stdc_bit_floor_ull "unsigned long long value"
+.Ft typeof Ns Pq Em value
+.Fn stdc_bit_floor "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_bit_floor_ Ns Em type Ns ()
+family of functions rounds
+.Fa value
+down to the previous power of\~2, where
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_bit_floor "value"
+type-generic macro picks the appropriate
+.Nm stdc_bit_floor_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns
+.Fa value
+round down to the previous power of\~2.
+If
+.Fa value
+is equal to zero,
+zero is returned.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_bit_ceil 3
+.Sh STANDARDS
+The
+.Nm stdc_bit_floor_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_bit_floor
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_bit_floor_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_bit_floor
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_bit_width.3 b/lib/libc/stdbit/stdc_bit_width.3
new file mode 100644
index 000000000000..8d59886818d3
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_width.3
@@ -0,0 +1,104 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_BIT_WIDTH 3
+.Os
+.Sh NAME
+.Nm stdc_bit_width
+.Nd find the first trailing one in an intege
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_bit_width_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_bit_width_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_bit_width_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_bit_width_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_bit_width_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_bit_width "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_bit_width_ Ns Em type Ns ()
+family of functions returns the number of bits needed to represent
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_bit_width "value"
+type-generic macro picks the appropriate
+.Nm stdc_bit_width_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Pp
+Functions
+.Fn stdc_bit_width_ui ,
+.Fn stdc_bit_width_ul ,
+and
+.Fn stdc_bit_width_ull
+are identical to
+.Bx 4.3
+functions
+.Xr fls 3 ,
+.Xr flsl 3 ,
+and
+.Xr flsll 3
+respectively, except for operating on unsigned instead of signed values.
+.Sh RETURN VALUES
+Returns the least number of bits needed to represent
+.Fa value .
+If
+.Fa value
+is zero, the return value is zero.
+Otherwise it is
+.EQ
+1 + \(lf log sub 2 italic value \(rf .
+.EN
+.Sh SEE ALSO
+.Xr bit_fls 3 ,
+.Xr fls 3 ,
+.Xr flsl 3 ,
+.Xr flsll 3 ,
+.Xr stdbit 3 ,
+.Xr stdc_count_leading_zeros 3 ,
+.Xr stdc_first_leading_one 3
+.Sh STANDARDS
+The
+.Nm stdc_bit_width_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_bit_width
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_bit_width_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_bit_width
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_count_ones.3 b/lib/libc/stdbit/stdc_count_ones.3
new file mode 100644
index 000000000000..6de92216c24b
--- /dev/null
+++ b/lib/libc/stdbit/stdc_count_ones.3
@@ -0,0 +1,85 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_COUNT_ONES 3
+.Os
+.Sh NAME
+.Nm stdc_count_ones
+.Nd count the ones in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_count_ones_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_count_ones_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_count_ones_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_count_ones_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_count_ones_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_count_ones "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_count_ones_ Ns Em type Ns ()
+family of functions returns the number of bits set to\~1 in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+This is also known as the
+.Dq population count
+(popcount) or
+.Dq Hamming weight
+operation.
+The
+.Fn stdc_count_ones "value"
+type-generic macro picks the appropriate
+.Nm stdc_count_ones_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the number of bits set to\~1 in
+.Fa value .
+.Sh SEE ALSO
+.Xr bit_count 3 ,
+.Xr stdbit 3 ,
+.Xr stdc_count_zeros 3 ,
+.Xr stdc_has_single_bit 3
+.Sh STANDARDS
+The
+.Nm stdc_count_ones_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_count_ones
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_count_ones_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_count_ones
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_count_zeros.3 b/lib/libc/stdbit/stdc_count_zeros.3
new file mode 100644
index 000000000000..762ba62d3793
--- /dev/null
+++ b/lib/libc/stdbit/stdc_count_zeros.3
@@ -0,0 +1,84 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_COUNT_ZEROS 3
+.Os
+.Sh NAME
+.Nm stdc_count_zeros
+.Nd count the zeros in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_count_zeros_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_count_zeros_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_count_zeros_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_count_zeros_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_count_zeros_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_count_zeros "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_count_zeros_ Ns Em type Ns ()
+family of functions returns the number of bits set to\~0 in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+This is also known as the
+.Dq population count
+(popcount) or
+.Dq Hamming weight
+of the complement of
+.Fa value .
+The
+.Fn stdc_count_zeros "value"
+type-generic macro picks the appropriate
+.Nm stdc_count_zeros_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the number of bits set to\~0 in
+.Fa value .
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_count_ones 3
+.Sh STANDARDS
+The
+.Nm stdc_count_zeros_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_count_zeros
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_count_zeros_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_count_zeros
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_first_leading_one.3 b/lib/libc/stdbit/stdc_first_leading_one.3
new file mode 100644
index 000000000000..48f62d997043
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_leading_one.3
@@ -0,0 +1,93 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_FIRST_LEADING_ONE 3
+.Os
+.Sh NAME
+.Nm stdc_first_leading_one
+.Nd find the first leading one in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_first_leading_one_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_first_leading_one_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_first_leading_one_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_first_leading_one_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_first_leading_one_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_first_leading_one "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_first_leading_one_ Ns Em type Ns ()
+family of functions returns the index of the most significant set bit in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_first_leading_one "value"
+type-generic macro picks the appropriate
+.Nm stdc_first_leading_one_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the index of the most significant set bit in
+.Fa value .
+The bits are numbered such that the most significant bit has number\~1,
+and the least significant bit has number
+.Ms w
+where
+.Ms w
+is the number of bits in the type of
+.Fa value .
+If no bits are set in
+.Fa value
+(i.\^e.\&
+.Fa value
+is zero), zero is returned.
+.Sh SEE ALSO
+.Xr fls 3 ,
+.Xr stdbit 3 ,
+.Xr stdc_leading_zeros 3 ,
+.Xr stdc_first_leading_zero 3 ,
+.Xr stdc_first_trailing_one 3
+.Sh STANDARDS
+The
+.Nm stdc_first_leading_one_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_leading_one
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_first_leading_one_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_leading_one
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_first_leading_zero.3 b/lib/libc/stdbit/stdc_first_leading_zero.3
new file mode 100644
index 000000000000..317b6263acb0
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_leading_zero.3
@@ -0,0 +1,92 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_FIRST_LEADING_ZERO 3
+.Os
+.Sh NAME
+.Nm stdc_first_leading_zero
+.Nd find the first leading zero in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_first_leading_zero_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_first_leading_zero_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_first_leading_zero_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_first_leading_zero_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_first_leading_zero_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_first_leading_zero "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_first_leading_zero_ Ns Em type Ns ()
+family of functions returns the index of the most significant clear bit in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_first_leading_zero "value"
+type-generic macro picks the appropriate
+.Nm stdc_first_leading_zero_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the index of the most significant clear bit in
+.Fa value .
+The bits are numbered such that the most significant bit has number\~1,
+and the least significant bit has number
+.Ms w
+where
+.Ms w
+is the number of bits in the type of
+.Fa value .
+If no bits are clear in
+.Fa value
+(i.\^e.\&
+.Fa value
+is the bitwise complement of zero), zero is returned.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_leading_ones 3 ,
+.Xr stdc_first_leading_ones 3 ,
+.Xr stdc_first_trailing_zero 3
+.Sh STANDARDS
+The
+.Nm stdc_first_leading_zero_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_leading_zero
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_first_leading_zero_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_leading_zero
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_first_trailing_one.3 b/lib/libc/stdbit/stdc_first_trailing_one.3
new file mode 100644
index 000000000000..0b590ac39732
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_trailing_one.3
@@ -0,0 +1,110 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_FIRST_TRAILING_ONE 3
+.Os
+.Sh NAME
+.Nm stdc_first_trailing_one
+.Nd find the first trailing one in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_first_trailing_one_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_first_trailing_one_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_first_trailing_one_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_first_trailing_one_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_first_trailing_one_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_first_trailing_one "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_first_trailing_one_ Ns Em type Ns ()
+family of functions returns the index of the least significant set bit in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_first_trailing_one "value"
+type-generic macro picks the appropriate
+.Nm stdc_first_trailing_one_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Pp
+Functions
+.Fn stdc_first_trailing_one_ui ,
+.Fn stdc_first_trailing_one_ul ,
+and
+.Fn stdc_first_trailing_one_ull
+are identical to
+.Bx 4.3
+functions
+.Xr ffs 3 ,
+.Xr ffsl 3 ,
+and
+.Xr ffsll 3
+respectively, except for operating on unsigned instead of signed values.
+.Sh RETURN VALUES
+Returns the index of the least significant set bit in
+.Fa value .
+The bits are numbered such that the least significant bit has number\~1,
+and the most significant bit has number
+.Ms w
+where
+.Ms w
+is the number of bits in the type of
+.Fa value .
+If no bits are set in
+.Fa value
+(i.\^e.\&
+.Fa value
+is zero), one is returned.
+.Sh SEE ALSO
+.Xr bit_ffs 3 ,
+.Xr ffs 3 ,
+.Xr ffsl 3 ,
+.Xr ffsll 3 ,
+.Xr stdbit 3 ,
+.Xr stdc_trailing_zeros 3 ,
+.Xr stdc_first_trailing_zero 3 ,
+.Xr stdc_first_leading_one 3
+.Sh STANDARDS
+The
+.Nm stdc_first_trailing_one_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_trailing_one
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_first_trailing_one_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_trailing_one
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_first_trailing_zero.3 b/lib/libc/stdbit/stdc_first_trailing_zero.3
new file mode 100644
index 000000000000..bc4f7982d765
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_trailing_zero.3
@@ -0,0 +1,93 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_FIRST_TRAILING_ZERO 3
+.Os
+.Sh NAME
+.Nm stdc_first_trailing_zero
+.Nd find the first trailing zero in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_first_trailing_zero_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_first_trailing_zero_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_first_trailing_zero_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_first_trailing_zero_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_first_trailing_zero_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_first_trailing_zero "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
+family of functions returns the index of the least significant clear bit in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_first_trailing_zero "value"
+type-generic macro picks the appropriate
+.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the index of the least significant clear bit in
+.Fa value .
+The bits are numbered such that the least significant bit has number\~1,
+and the most significant bit has number
+.Ms w
+where
+.Ms w
+is the number of bits in the type of
+.Fa value .
+If no bits are clear in
+.Fa value
+(i.\^e.\&
+.Fa value
+is the bitwise complement of zero), zero is returned.
+.Sh SEE ALSO
+.Xr bit_ffc 3 ,
+.Xr stdbit 3 ,
+.Xr stdc_trailing_ones 3 ,
+.Xr stdc_first_trailing_ones 3 ,
+.Xr stdc_first_leading_zero 3
+.Sh STANDARDS
+The
+.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_trailing_zero
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_first_trailing_zero
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_has_single_bit.3 b/lib/libc/stdbit/stdc_has_single_bit.3
new file mode 100644
index 000000000000..8f82c552216a
--- /dev/null
+++ b/lib/libc/stdbit/stdc_has_single_bit.3
@@ -0,0 +1,98 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_HAS_SINGLE_BIT 3
+.Os
+.Sh NAME
+.Nm stdc_has_single_bit
+.Nd check for single bit set
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft bool
+.Fn stdc_has_single_bit_uc "unsigned char value"
+.Ft bool
+.Fn stdc_has_single_bit_us "unsigned short value"
+.Ft bool
+.Fn stdc_has_single_bit_ui "unsigned int value"
+.Ft bool
+.Fn stdc_has_single_bit_ul "unsigned long value"
+.Ft bool
+.Fn stdc_has_single_bit_ull "unsigned long long value"
+.Ft bool
+.Fn stdc_has_single_bit "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_has_single_bit_ Ns Em type Ns ()
+family of functions checks if there is exactly one bit
+set in
+.Fa value ,
+where
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_has_single_bit "value"
+type-generic macro picks the appropriate
+.Nm stdc_has_single_bit_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Pp
+The functions in this family behave similarly to the
+.Fn powerof2 "value"
+macro of
+.In sys/param.h ,
+but differ when
+.Fa value
+is zero: while
+.Fn powerof2
+considers zero to be a power of two,
+.Fn stdc_has_single_bit
+does not.
+.Sh RETURN VALUES
+Returns
+.Sy true
+if exactly one bit is set in
+.Fa value ,
+otherwise returns
+.Sy false .
+I.\^e. the function determines if
+.Fa value
+is a power of two.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_count_ones 3
+.Sh STANDARDS
+The
+.Nm stdc_has_single_bit_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_has_single_bit
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_has_single_bit_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_has_single_bit
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_leading_ones.3 b/lib/libc/stdbit/stdc_leading_ones.3
new file mode 100644
index 000000000000..6cf7989b73ea
--- /dev/null
+++ b/lib/libc/stdbit/stdc_leading_ones.3
@@ -0,0 +1,86 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_LEADING_ONES 3
+.Os
+.Sh NAME
+.Nm stdc_leading_ones
+.Nd find the number of leading ones in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_leading_ones_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_leading_ones_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_leading_ones_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_leading_ones_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_leading_ones_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_leading_ones "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_leading_ones_ Ns Em type Ns ()
+family of functions returns the number of leading ones in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_leading_ones "value"
+type-generic macro picks the appropriate
+.Nm stdc_leading_ones_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the number of leading ones in
+.Fa value .
+If
+.Fa value
+is all ones,
+the total number of bits in the type of
+.Fa value
+is returned.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_leading_zeros 3 ,
+.Xr stdc_trailing_ones 3 ,
+.Xr stdc_first_leading_zero 3
+.Sh STANDARDS
+The
+.Nm stdc_leading_ones_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_leading_ones
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_leading_ones_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_leading_ones
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_leading_zeros.3 b/lib/libc/stdbit/stdc_leading_zeros.3
new file mode 100644
index 000000000000..7a7a203ac78c
--- /dev/null
+++ b/lib/libc/stdbit/stdc_leading_zeros.3
@@ -0,0 +1,86 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_LEADING_ZEROS 3
+.Os
+.Sh NAME
+.Nm stdc_leading_zeros
+.Nd find the number of leading zeros in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_leading_zeros_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_leading_zeros_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_leading_zeros_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_leading_zeros_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_leading_zeros_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_leading_zeros "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_leading_zeros_ Ns Em type Ns ()
+family of functions returns the number of leading zeros in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_leading_zeros "value"
+type-generic macro picks the appropriate
+.Nm stdc_leading_zeros_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the number of leading zeros in
+.Fa value .
+If
+.Fa value
+is all zeros,
+the total number of bits in the type of
+.Fa value
+is returned.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_leading_ones 3 ,
+.Xr stdc_trailing_zeros 3 ,
+.Xr stdc_first_leading_one 3
+.Sh STANDARDS
+The
+.Nm stdc_leading_zeros_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_leading_zeros
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_leading_zeros_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_leading_zeros
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_trailing_ones.3 b/lib/libc/stdbit/stdc_trailing_ones.3
new file mode 100644
index 000000000000..96277506fc17
--- /dev/null
+++ b/lib/libc/stdbit/stdc_trailing_ones.3
@@ -0,0 +1,86 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_TRAILING_ONES 3
+.Os
+.Sh NAME
+.Nm stdc_trailing_ones
+.Nd find the number of trailing ones in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_trailing_ones_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_trailing_ones_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_trailing_ones_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_trailing_ones_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_trailing_ones_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_trailing_ones "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_trailing_ones_ Ns Em type Ns ()
+family of functions returns the number of trailing ones in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_trailing_ones "value"
+type-generic macro picks the appropriate
+.Nm stdc_trailing_ones_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the number of trailing ones in
+.Fa value .
+If
+.Fa value
+is all ones,
+the total number of bits in the type of
+.Fa value
+is returned.
+.Sh SEE ALSO
+.Xr stdbit 3 ,
+.Xr stdc_leading_ones 3 ,
+.Xr stdc_trailing_zeros 3 ,
+.Xr stdc_first_trailing_zero 3
+.Sh STANDARDS
+The
+.Nm stdc_trailing_ones_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_trailing_ones
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_trailing_ones_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_trailing_ones
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org
diff --git a/lib/libc/stdbit/stdc_trailing_zeros.3 b/lib/libc/stdbit/stdc_trailing_zeros.3
new file mode 100644
index 000000000000..4bc675590ee7
--- /dev/null
+++ b/lib/libc/stdbit/stdc_trailing_zeros.3
@@ -0,0 +1,87 @@
+.\"
+.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd November 9, 2025
+.Dt STDC_TRAILING_ZEROS 3
+.Os
+.Sh NAME
+.Nm stdc_trailing_zeros
+.Nd find the number of trailing zeros in an integer
+.Sh SYNOPSIS
+.Lb libc
+.In stdbit.h
+.Ft unsigned int
+.Fn stdc_trailing_zeros_uc "unsigned char value"
+.Ft unsigned int
+.Fn stdc_trailing_zeros_us "unsigned short value"
+.Ft unsigned int
+.Fn stdc_trailing_zeros_ui "unsigned int value"
+.Ft unsigned int
+.Fn stdc_trailing_zeros_ul "unsigned long value"
+.Ft unsigned int
+.Fn stdc_trailing_zeros_ull "unsigned long long value"
+.Ft unsigned int
+.Fn stdc_trailing_zeros "value"
+.Sh DESCRIPTION
+The
+.Nm stdc_trailing_zeros_ Ns Em type Ns ()
+family of functions returns the number of trailing zeros in
+.Fa value ,
+where 
+.Fa value
+is of type
+.Va unsigned char ,
+.Va unsigned short ,
+.Va unsigned int ,
+.Va unsigned long ,
+or
+.Va unsigned long long
+for
+.Em type
+being
+.Sy uc ,
+.Sy us ,
+.Sy ui ,
+.Sy ul ,
+or
+.Sy ull
+respectively.
+The
+.Fn stdc_trailing_zeros "value"
+type-generic macro picks the appropriate
+.Nm stdc_trailing_zeros_ Ns Em type Ns ()
+function based on the type of
+.Fa value .
+.Sh RETURN VALUES
+Returns the number of trailing zeros in
+.Fa value .
+If
+.Fa value
+is all zeros,
+the total number of bits in the type of
+.Fa value
+is returned.
+.Sh SEE ALSO
+.Xr ffs 3 ,
+.Xr stdbit 3 ,
+.Xr stdc_leading_zeros 3 ,
+.Xr stdc_trailing_ones 3 ,
+.Xr stdc_first_trailing_one 3
+.Sh STANDARDS
+The
+.Nm stdc_trailing_zeros_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_trailing_zeros
+type-generic macro conform to
+.St -isoC-2023 .
+.Sh HISTORY
+The
+.Nm stdc_trailing_zeros_ Ns Em type Ns ()
+family of functions and the
+.Fn stdc_trailing_zeros
+type-generic macro were added in
+.Fx 15.1.
+.Sh AUTHOR
+.An Robert Clausecker Aq Mt fuz@FreeBSD.org