git: 6296500a85c8 - main - libc: implement C23 <stdbit.h> functions
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Date: Sun, 30 Nov 2025 19:22:11 UTC
The branch main has been updated by fuz:
URL: https://cgit.FreeBSD.org/src/commit/?id=6296500a85c8474e3ff3fe2f8e4a9d56dd0acd64
commit 6296500a85c8474e3ff3fe2f8e4a9d56dd0acd64
Author: Robert Clausecker <fuz@FreeBSD.org>
AuthorDate: 2025-11-18 17:32:53 +0000
Commit: Robert Clausecker <fuz@FreeBSD.org>
CommitDate: 2025-11-30 19:21:52 +0000
libc: implement C23 <stdbit.h> functions
This new header complies with ISO/IEC 9899:2024 (C23).
Contrary to glibc, we do not provide inline definitions in
<stdbit.h> as we expect our system compiler to soon recognise
these as builtins anyway.
Relnotes: yes
MFC after: 1 month
Reviewed by: adrian
Approved by: markj (mentor)
Differential Revision: https://reviews.freebsd.org/D53657
---
include/Makefile | 4 +-
include/stdbit.h | 124 +++++++++++++++++++++++++++++
lib/libc/Makefile | 1 +
lib/libc/stdbit/Makefile.inc | 19 +++++
lib/libc/stdbit/Symbol.map | 85 ++++++++++++++++++++
lib/libc/stdbit/stdc_bit_ceil.c | 71 +++++++++++++++++
lib/libc/stdbit/stdc_bit_floor.c | 53 ++++++++++++
lib/libc/stdbit/stdc_bit_width.c | 53 ++++++++++++
lib/libc/stdbit/stdc_count_ones.c | 38 +++++++++
lib/libc/stdbit/stdc_count_zeros.c | 38 +++++++++
lib/libc/stdbit/stdc_first_leading_one.c | 57 +++++++++++++
lib/libc/stdbit/stdc_first_leading_zero.c | 57 +++++++++++++
lib/libc/stdbit/stdc_first_trailing_one.c | 52 ++++++++++++
lib/libc/stdbit/stdc_first_trailing_zero.c | 53 ++++++++++++
lib/libc/stdbit/stdc_has_single_bit.c | 38 +++++++++
lib/libc/stdbit/stdc_leading_ones.c | 60 ++++++++++++++
lib/libc/stdbit/stdc_leading_zeros.c | 60 ++++++++++++++
lib/libc/stdbit/stdc_trailing_ones.c | 56 +++++++++++++
lib/libc/stdbit/stdc_trailing_zeros.c | 56 +++++++++++++
19 files changed, 973 insertions(+), 2 deletions(-)
diff --git a/include/Makefile b/include/Makefile
index b8cbf0ecc1c2..028e5055cc91 100644
--- a/include/Makefile
+++ b/include/Makefile
@@ -29,8 +29,8 @@ INCS= a.out.h ar.h assert.h bitstring.h byteswap.h \
pthread_np.h pwd.h ranlib.h readpassphrase.h regex.h \
res_update.h resolv.h runetype.h sched.h \
search.h semaphore.h setjmp.h \
- signal.h spawn.h stab.h stdalign.h stdbool.h stdckdint.h stddef.h \
- stdnoreturn.h stdio.h stdlib.h string.h stringlist.h \
+ signal.h spawn.h stab.h stdalign.h stdbit.h stdbool.h stdckdint.h \
+ stddef.h stdnoreturn.h stdio.h stdlib.h string.h stringlist.h \
strings.h sysexits.h tar.h termios.h tgmath.h \
time.h timeconv.h timers.h ttyent.h \
uchar.h ulimit.h unistd.h utime.h utmpx.h uuid.h varargs.h \
diff --git a/include/stdbit.h b/include/stdbit.h
new file mode 100644
index 000000000000..a529676bed4b
--- /dev/null
+++ b/include/stdbit.h
@@ -0,0 +1,124 @@
+/*-
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#ifndef __STDC_VERSION_STDBIT_H__
+#define __STDC_VERSION_STDBIT_H__ 202311L
+
+#include <sys/cdefs.h>
+
+/* byte order */
+#define __STDC_ENDIAN_LITTLE__ __ORDER_LITTLE_ENDIAN__
+#define __STDC_ENDIAN_BIG__ __ORDER_BIG_ENDIAN__
+#define __STDC_ENDIAN_NATIVE__ __BYTE_ORDER__
+
+#define __generic_bitfunc(func, x) (_Generic(x, \
+ unsigned char: func ## _uc, \
+ unsigned short: func ## _us, \
+ unsigned int: func ## _ui, \
+ unsigned long: func ## _ul, \
+ unsigned long long: func ## _ull)(x))
+
+__BEGIN_DECLS
+unsigned int stdc_leading_zeros_uc(unsigned char) __pure2;
+unsigned int stdc_leading_zeros_us(unsigned short) __pure2;
+unsigned int stdc_leading_zeros_ui(unsigned int) __pure2;
+unsigned int stdc_leading_zeros_ul(unsigned long) __pure2;
+unsigned int stdc_leading_zeros_ull(unsigned long long) __pure2;
+#define stdc_leading_zeros(x) __generic_bitfunc(stdc_leading_zeros, x)
+
+unsigned int stdc_leading_ones_uc(unsigned char) __pure2;
+unsigned int stdc_leading_ones_us(unsigned short) __pure2;
+unsigned int stdc_leading_ones_ui(unsigned int) __pure2;
+unsigned int stdc_leading_ones_ul(unsigned long) __pure2;
+unsigned int stdc_leading_ones_ull(unsigned long long) __pure2;
+#define stdc_leading_ones(x) __generic_bitfunc(stdc_leading_ones, x)
+
+unsigned int stdc_trailing_zeros_uc(unsigned char) __pure2;
+unsigned int stdc_trailing_zeros_us(unsigned short) __pure2;
+unsigned int stdc_trailing_zeros_ui(unsigned int) __pure2;
+unsigned int stdc_trailing_zeros_ul(unsigned long) __pure2;
+unsigned int stdc_trailing_zeros_ull(unsigned long long) __pure2;
+#define stdc_trailing_zeros(x) __generic_bitfunc(stdc_trailing_zeros, x)
+
+unsigned int stdc_trailing_ones_uc(unsigned char) __pure2;
+unsigned int stdc_trailing_ones_us(unsigned short) __pure2;
+unsigned int stdc_trailing_ones_ui(unsigned int) __pure2;
+unsigned int stdc_trailing_ones_ul(unsigned long) __pure2;
+unsigned int stdc_trailing_ones_ull(unsigned long long) __pure2;
+#define stdc_trailing_ones(x) __generic_bitfunc(stdc_trailing_ones, x)
+
+unsigned int stdc_first_leading_zero_uc(unsigned char) __pure2;
+unsigned int stdc_first_leading_zero_us(unsigned short) __pure2;
+unsigned int stdc_first_leading_zero_ui(unsigned int) __pure2;
+unsigned int stdc_first_leading_zero_ul(unsigned long) __pure2;
+unsigned int stdc_first_leading_zero_ull(unsigned long long) __pure2;
+#define stdc_first_leading_zero(x) __generic_bitfunc(stdc_first_leading_zero, x)
+
+unsigned int stdc_first_leading_one_uc(unsigned char) __pure2;
+unsigned int stdc_first_leading_one_us(unsigned short) __pure2;
+unsigned int stdc_first_leading_one_ui(unsigned int) __pure2;
+unsigned int stdc_first_leading_one_ul(unsigned long) __pure2;
+unsigned int stdc_first_leading_one_ull(unsigned long long) __pure2;
+#define stdc_first_leading_one(x) __generic_bitfunc(stdc_first_leading_one, x)
+
+unsigned int stdc_first_trailing_zero_uc(unsigned char) __pure2;
+unsigned int stdc_first_trailing_zero_us(unsigned short) __pure2;
+unsigned int stdc_first_trailing_zero_ui(unsigned int) __pure2;
+unsigned int stdc_first_trailing_zero_ul(unsigned long) __pure2;
+unsigned int stdc_first_trailing_zero_ull(unsigned long long) __pure2;
+#define stdc_first_trailing_zero(x) __generic_bitfunc(stdc_first_trailing_zero, x)
+
+unsigned int stdc_first_trailing_one_uc(unsigned char) __pure2;
+unsigned int stdc_first_trailing_one_us(unsigned short) __pure2;
+unsigned int stdc_first_trailing_one_ui(unsigned int) __pure2;
+unsigned int stdc_first_trailing_one_ul(unsigned long) __pure2;
+unsigned int stdc_first_trailing_one_ull(unsigned long long) __pure2;
+#define stdc_first_trailing_one(x) __generic_bitfunc(stdc_first_trailing_one, x)
+
+unsigned int stdc_count_zeros_uc(unsigned char) __pure2;
+unsigned int stdc_count_zeros_us(unsigned short) __pure2;
+unsigned int stdc_count_zeros_ui(unsigned int) __pure2;
+unsigned int stdc_count_zeros_ul(unsigned long) __pure2;
+unsigned int stdc_count_zeros_ull(unsigned long long) __pure2;
+#define stdc_count_zeros(x) __generic_bitfunc(stdc_count_zeros, x)
+
+unsigned int stdc_count_ones_uc(unsigned char) __pure2;
+unsigned int stdc_count_ones_us(unsigned short) __pure2;
+unsigned int stdc_count_ones_ui(unsigned int) __pure2;
+unsigned int stdc_count_ones_ul(unsigned long) __pure2;
+unsigned int stdc_count_ones_ull(unsigned long long) __pure2;
+#define stdc_count_ones(x) __generic_bitfunc(stdc_count_ones, x)
+
+_Bool stdc_has_single_bit_uc(unsigned char) __pure2;
+_Bool stdc_has_single_bit_us(unsigned short) __pure2;
+_Bool stdc_has_single_bit_ui(unsigned int) __pure2;
+_Bool stdc_has_single_bit_ul(unsigned long) __pure2;
+_Bool stdc_has_single_bit_ull(unsigned long long) __pure2;
+#define stdc_has_single_bit(x) __generic_bitfunc(stdc_has_single_bit, x)
+
+unsigned int stdc_bit_width_uc(unsigned char) __pure2;
+unsigned int stdc_bit_width_us(unsigned short) __pure2;
+unsigned int stdc_bit_width_ui(unsigned int) __pure2;
+unsigned int stdc_bit_width_ul(unsigned long) __pure2;
+unsigned int stdc_bit_width_ull(unsigned long long) __pure2;
+#define stdc_bit_width(x) __generic_bitfunc(stdc_bit_width, x)
+
+unsigned char stdc_bit_floor_uc(unsigned char) __pure2;
+unsigned short stdc_bit_floor_us(unsigned short) __pure2;
+unsigned stdc_bit_floor_ui(unsigned int) __pure2;
+unsigned long stdc_bit_floor_ul(unsigned long) __pure2;
+unsigned long long stdc_bit_floor_ull(unsigned long long) __pure2;
+#define stdc_bit_floor(x) __generic_bitfunc(stdc_bit_floor, x)
+
+unsigned char stdc_bit_ceil_uc(unsigned char) __pure2;
+unsigned short stdc_bit_ceil_us(unsigned short) __pure2;
+unsigned int stdc_bit_ceil_ui(unsigned int) __pure2;
+unsigned long stdc_bit_ceil_ul(unsigned long) __pure2;
+unsigned long long stdc_bit_ceil_ull(unsigned long long) __pure2;
+#define stdc_bit_ceil(x) __generic_bitfunc(stdc_bit_ceil, x)
+__END_DECLS
+
+#endif /* __STDC_VERSION_STDBIT_H__ */
diff --git a/lib/libc/Makefile b/lib/libc/Makefile
index 8705568f6d34..34474cfa9fe4 100644
--- a/lib/libc/Makefile
+++ b/lib/libc/Makefile
@@ -118,6 +118,7 @@ NOASM=
.endif
.include "${LIBC_SRCTOP}/regex/Makefile.inc"
.include "${LIBC_SRCTOP}/resolv/Makefile.inc"
+.include "${LIBC_SRCTOP}/stdbit/Makefile.inc"
.include "${LIBC_SRCTOP}/stdio/Makefile.inc"
.include "${LIBC_SRCTOP}/stdlib/Makefile.inc"
.include "${LIBC_SRCTOP}/stdtime/Makefile.inc"
diff --git a/lib/libc/stdbit/Makefile.inc b/lib/libc/stdbit/Makefile.inc
new file mode 100644
index 000000000000..2ea96d2b6dfe
--- /dev/null
+++ b/lib/libc/stdbit/Makefile.inc
@@ -0,0 +1,19 @@
+# sources for <stdbit.h>
+.PATH: ${LIBC_SRCTOP}/stdbit
+
+SRCS+= stdc_bit_ceil.c \
+ stdc_bit_floor.c \
+ stdc_bit_width.c \
+ stdc_count_ones.c \
+ stdc_count_zeros.c \
+ stdc_first_leading_one.c \
+ stdc_first_leading_zero.c \
+ stdc_first_trailing_one.c \
+ stdc_first_trailing_zero.c \
+ stdc_has_single_bit.c \
+ stdc_leading_ones.c \
+ stdc_leading_zeros.c \
+ stdc_trailing_ones.c \
+ stdc_trailing_zeros.c
+
+SYM_MAPS+=${LIBC_SRCTOP}/stdbit/Symbol.map
diff --git a/lib/libc/stdbit/Symbol.map b/lib/libc/stdbit/Symbol.map
new file mode 100644
index 000000000000..7014d6984c07
--- /dev/null
+++ b/lib/libc/stdbit/Symbol.map
@@ -0,0 +1,85 @@
+FBSD_1.9 {
+ stdc_leading_zeros_uc;
+ stdc_leading_zeros_us;
+ stdc_leading_zeros_ui;
+ stdc_leading_zeros_ul;
+ stdc_leading_zeros_ull;
+
+ stdc_leading_ones_uc;
+ stdc_leading_ones_us;
+ stdc_leading_ones_ui;
+ stdc_leading_ones_ul;
+ stdc_leading_ones_ull;
+
+ stdc_trailing_zeros_uc;
+ stdc_trailing_zeros_us;
+ stdc_trailing_zeros_ui;
+ stdc_trailing_zeros_ul;
+ stdc_trailing_zeros_ull;
+
+ stdc_trailing_ones_uc;
+ stdc_trailing_ones_us;
+ stdc_trailing_ones_ui;
+ stdc_trailing_ones_ul;
+ stdc_trailing_ones_ull;
+
+ stdc_first_leading_zero_uc;
+ stdc_first_leading_zero_us;
+ stdc_first_leading_zero_ui;
+ stdc_first_leading_zero_ul;
+ stdc_first_leading_zero_ull;
+
+ stdc_first_leading_one_uc;
+ stdc_first_leading_one_us;
+ stdc_first_leading_one_ui;
+ stdc_first_leading_one_ul;
+ stdc_first_leading_one_ull;
+
+ stdc_first_trailing_zero_uc;
+ stdc_first_trailing_zero_us;
+ stdc_first_trailing_zero_ui;
+ stdc_first_trailing_zero_ul;
+ stdc_first_trailing_zero_ull;
+
+ stdc_first_trailing_one_uc;
+ stdc_first_trailing_one_us;
+ stdc_first_trailing_one_ui;
+ stdc_first_trailing_one_ul;
+ stdc_first_trailing_one_ull;
+
+ stdc_count_zeros_uc;
+ stdc_count_zeros_us;
+ stdc_count_zeros_ui;
+ stdc_count_zeros_ul;
+ stdc_count_zeros_ull;
+
+ stdc_count_ones_uc;
+ stdc_count_ones_us;
+ stdc_count_ones_ui;
+ stdc_count_ones_ul;
+ stdc_count_ones_ull;
+
+ stdc_has_single_bit_uc;
+ stdc_has_single_bit_us;
+ stdc_has_single_bit_ui;
+ stdc_has_single_bit_ul;
+ stdc_has_single_bit_ull;
+
+ stdc_bit_width_uc;
+ stdc_bit_width_us;
+ stdc_bit_width_ui;
+ stdc_bit_width_ul;
+ stdc_bit_width_ull;
+
+ stdc_bit_floor_uc;
+ stdc_bit_floor_us;
+ stdc_bit_floor_ui;
+ stdc_bit_floor_ul;
+ stdc_bit_floor_ull;
+
+ stdc_bit_ceil_uc;
+ stdc_bit_ceil_us;
+ stdc_bit_ceil_ui;
+ stdc_bit_ceil_ul;
+ stdc_bit_ceil_ull;
+};
diff --git a/lib/libc/stdbit/stdc_bit_ceil.c b/lib/libc/stdbit/stdc_bit_ceil.c
new file mode 100644
index 000000000000..2dfd7bbcbea2
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_ceil.c
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <assert.h>
+#include <limits.h>
+#include <stdbit.h>
+
+/* Ensure we don't shift 1U out of range. */
+static_assert(UCHAR_WIDTH < UINT_WIDTH,
+ "stdc_bit_ceil_uc needs UCHAR_WIDTH < UINT_WIDTH");
+
+unsigned char
+stdc_bit_ceil_uc(unsigned char x)
+{
+ if (x <= 1)
+ return (1);
+
+ return (1U << (UINT_WIDTH - __builtin_clz(x - 1)));
+}
+
+/* Ensure we don't shift 1U out of range. */
+static_assert(USHRT_WIDTH < UINT_WIDTH,
+ "stdc_bit_ceil_us needs USHRT_WIDTH < UINT_WIDTH");
+
+unsigned short
+stdc_bit_ceil_us(unsigned short x)
+{
+ if (x <= 1)
+ return (1);
+
+ return (1U << (UINT_WIDTH - __builtin_clz(x - 1)));
+}
+
+unsigned int
+stdc_bit_ceil_ui(unsigned int x)
+{
+ if (x <= 1)
+ return (1);
+
+ if (x > UINT_MAX/2 + 1)
+ return (0);
+
+ return (1U << (UINT_WIDTH - __builtin_clz(x - 1)));
+}
+
+unsigned long
+stdc_bit_ceil_ul(unsigned long x)
+{
+ if (x <= 1)
+ return (1);
+
+ if (x > ULONG_MAX/2 + 1)
+ return (0);
+
+ return (1UL << (ULONG_WIDTH - __builtin_clzl(x - 1)));
+}
+
+unsigned long long
+stdc_bit_ceil_ull(unsigned long long x)
+{
+ if (x <= 1)
+ return (1);
+
+ if (x > ULLONG_MAX/2 + 1)
+ return (0);
+
+ return (1ULL << (ULLONG_WIDTH - __builtin_clzll(x - 1)));
+}
diff --git a/lib/libc/stdbit/stdc_bit_floor.c b/lib/libc/stdbit/stdc_bit_floor.c
new file mode 100644
index 000000000000..0a491d6ec7b3
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_floor.c
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned char
+stdc_bit_floor_uc(unsigned char x)
+{
+ if (x == 0)
+ return (0);
+
+ return (1U << (UINT_WIDTH - __builtin_clz(x) - 1));
+}
+
+unsigned short
+stdc_bit_floor_us(unsigned short x)
+{
+ if (x == 0)
+ return (0);
+
+ return (1U << (UINT_WIDTH - __builtin_clz(x) - 1));
+}
+
+unsigned int
+stdc_bit_floor_ui(unsigned int x)
+{
+ if (x == 0)
+ return (0);
+
+ return (1U << (UINT_WIDTH - __builtin_clz(x) - 1));
+}
+
+unsigned long
+stdc_bit_floor_ul(unsigned long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (1UL << (ULONG_WIDTH - __builtin_clzl(x) - 1));
+}
+
+unsigned long long
+stdc_bit_floor_ull(unsigned long long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (1ULL << (ULLONG_WIDTH - __builtin_clzll(x) - 1));
+}
diff --git a/lib/libc/stdbit/stdc_bit_width.c b/lib/libc/stdbit/stdc_bit_width.c
new file mode 100644
index 000000000000..e248fae48e9f
--- /dev/null
+++ b/lib/libc/stdbit/stdc_bit_width.c
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned int
+stdc_bit_width_uc(unsigned char x)
+{
+ if (x == 0)
+ return (0);
+
+ return (UINT_WIDTH - __builtin_clz(x));
+}
+
+unsigned int
+stdc_bit_width_us(unsigned short x)
+{
+ if (x == 0)
+ return (0);
+
+ return (UINT_WIDTH - __builtin_clz(x));
+}
+
+unsigned int
+stdc_bit_width_ui(unsigned int x)
+{
+ if (x == 0)
+ return (0);
+
+ return (UINT_WIDTH - __builtin_clz(x));
+}
+
+unsigned int
+stdc_bit_width_ul(unsigned long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (ULONG_WIDTH - __builtin_clzl(x));
+}
+
+unsigned int
+stdc_bit_width_ull(unsigned long long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (ULLONG_WIDTH - __builtin_clzll(x));
+}
diff --git a/lib/libc/stdbit/stdc_count_ones.c b/lib/libc/stdbit/stdc_count_ones.c
new file mode 100644
index 000000000000..c5198dca84df
--- /dev/null
+++ b/lib/libc/stdbit/stdc_count_ones.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned int
+stdc_count_ones_uc(unsigned char x)
+{
+ return (__builtin_popcount(x));
+}
+
+unsigned int
+stdc_count_ones_us(unsigned short x)
+{
+ return (__builtin_popcount(x));
+}
+
+unsigned int
+stdc_count_ones_ui(unsigned int x)
+{
+ return (__builtin_popcount(x));
+}
+
+unsigned int
+stdc_count_ones_ul(unsigned long x)
+{
+ return (__builtin_popcountl(x));
+}
+
+unsigned int
+stdc_count_ones_ull(unsigned long long x)
+{
+ return (__builtin_popcountll(x));
+}
diff --git a/lib/libc/stdbit/stdc_count_zeros.c b/lib/libc/stdbit/stdc_count_zeros.c
new file mode 100644
index 000000000000..35db965afcb5
--- /dev/null
+++ b/lib/libc/stdbit/stdc_count_zeros.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned int
+stdc_count_zeros_uc(unsigned char x)
+{
+ return (__builtin_popcount(x ^ UCHAR_MAX));
+}
+
+unsigned int
+stdc_count_zeros_us(unsigned short x)
+{
+ return (__builtin_popcount(x ^ USHRT_MAX));
+}
+
+unsigned int
+stdc_count_zeros_ui(unsigned int x)
+{
+ return (__builtin_popcount(~x));
+}
+
+unsigned int
+stdc_count_zeros_ul(unsigned long x)
+{
+ return (__builtin_popcountl(~x));
+}
+
+unsigned int
+stdc_count_zeros_ull(unsigned long long x)
+{
+ return (__builtin_popcountll(~x));
+}
diff --git a/lib/libc/stdbit/stdc_first_leading_one.c b/lib/libc/stdbit/stdc_first_leading_one.c
new file mode 100644
index 000000000000..de436856569f
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_leading_one.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned int
+stdc_first_leading_one_uc(unsigned char x)
+{
+ const int offset = UINT_WIDTH - UCHAR_WIDTH;
+
+ if (x == 0)
+ return (0);
+
+ return (__builtin_clz(x << offset) + 1);
+}
+
+unsigned int
+stdc_first_leading_one_us(unsigned short x)
+{
+ const int offset = UINT_WIDTH - USHRT_WIDTH;
+
+ if (x == 0)
+ return (0);
+
+ return (__builtin_clz(x << offset) + 1);
+}
+
+unsigned int
+stdc_first_leading_one_ui(unsigned int x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_clz(x) + 1);
+}
+
+unsigned int
+stdc_first_leading_one_ul(unsigned long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_clzl(x) + 1);
+}
+
+unsigned int
+stdc_first_leading_one_ull(unsigned long long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_clzll(x) + 1);
+}
diff --git a/lib/libc/stdbit/stdc_first_leading_zero.c b/lib/libc/stdbit/stdc_first_leading_zero.c
new file mode 100644
index 000000000000..e6609b51b648
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_leading_zero.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned int
+stdc_first_leading_zero_uc(unsigned char x)
+{
+ const int offset = UINT_WIDTH - UCHAR_WIDTH;
+
+ if (x == UCHAR_MAX)
+ return (0);
+
+ return (__builtin_clz(~(unsigned int)x << offset) + 1);
+}
+
+unsigned int
+stdc_first_leading_zero_us(unsigned short x)
+{
+ const int offset = UINT_WIDTH - USHRT_WIDTH;
+
+ if (x == USHRT_MAX)
+ return (0);
+
+ return (__builtin_clz(~(unsigned int)x << offset) + 1);
+}
+
+unsigned int
+stdc_first_leading_zero_ui(unsigned int x)
+{
+ if (x == ~0U)
+ return (0);
+
+ return (__builtin_clz(~x) + 1);
+}
+
+unsigned int
+stdc_first_leading_zero_ul(unsigned long x)
+{
+ if (x == ~0UL)
+ return (0);
+
+ return (__builtin_clzl(~x) + 1);
+}
+
+unsigned int
+stdc_first_leading_zero_ull(unsigned long long x)
+{
+ if (x == ~0ULL)
+ return (0);
+
+ return (__builtin_clzll(~x) + 1);
+}
diff --git a/lib/libc/stdbit/stdc_first_trailing_one.c b/lib/libc/stdbit/stdc_first_trailing_one.c
new file mode 100644
index 000000000000..22972758d25d
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_trailing_one.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <stdbit.h>
+
+unsigned int
+stdc_first_trailing_one_uc(unsigned char x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_ctz(x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_one_us(unsigned short x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_ctz(x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_one_ui(unsigned int x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_ctz(x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_one_ul(unsigned long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_ctzl(x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_one_ull(unsigned long long x)
+{
+ if (x == 0)
+ return (0);
+
+ return (__builtin_ctzll(x) + 1);
+}
diff --git a/lib/libc/stdbit/stdc_first_trailing_zero.c b/lib/libc/stdbit/stdc_first_trailing_zero.c
new file mode 100644
index 000000000000..27395c6977c3
--- /dev/null
+++ b/lib/libc/stdbit/stdc_first_trailing_zero.c
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <limits.h>
+#include <stdbit.h>
+
+unsigned int
+stdc_first_trailing_zero_uc(unsigned char x)
+{
+ if (x == UCHAR_MAX)
+ return (0);
+
+ return (__builtin_ctz(~x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_zero_us(unsigned short x)
+{
+ if (x == USHRT_MAX)
+ return (0);
+
+ return (__builtin_ctz(~x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_zero_ui(unsigned int x)
+{
+ if (x == ~0U)
+ return (0);
+
+ return (__builtin_ctz(~x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_zero_ul(unsigned long x)
+{
+ if (x == ~0UL)
+ return (0);
+
+ return (__builtin_ctzl(~x) + 1);
+}
+
+unsigned int
+stdc_first_trailing_zero_ull(unsigned long long x)
+{
+ if (x == ~0ULL)
+ return (0);
+
+ return (__builtin_ctzll(~x) + 1);
+}
diff --git a/lib/libc/stdbit/stdc_has_single_bit.c b/lib/libc/stdbit/stdc_has_single_bit.c
new file mode 100644
index 000000000000..e5f676265551
--- /dev/null
+++ b/lib/libc/stdbit/stdc_has_single_bit.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <stdbit.h>
+#include <stdbool.h>
+
+bool
+stdc_has_single_bit_uc(unsigned char x)
+{
+ return (x != 0 && (x & x - 1) == 0);
+}
+
+bool
+stdc_has_single_bit_us(unsigned short x)
+{
+ return (x != 0 && (x & x - 1) == 0);
+}
+
+bool
+stdc_has_single_bit_ui(unsigned int x)
+{
+ return (x != 0 && (x & x - 1) == 0);
+}
+
+bool
+stdc_has_single_bit_ul(unsigned long x)
+{
+ return (x != 0 && (x & x - 1) == 0);
+}
+
+bool
+stdc_has_single_bit_ull(unsigned long long x)
+{
+ return (x != 0 && (x & x - 1) == 0);
+}
diff --git a/lib/libc/stdbit/stdc_leading_ones.c b/lib/libc/stdbit/stdc_leading_ones.c
new file mode 100644
index 000000000000..79d3ec7f2065
--- /dev/null
+++ b/lib/libc/stdbit/stdc_leading_ones.c
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <assert.h>
+#include <limits.h>
+#include <stdbit.h>
+
+/* Avoid triggering undefined behavior if x == 0. */
+static_assert(UCHAR_WIDTH < UINT_WIDTH,
+ "stdc_leading_ones_uc needs UCHAR_WIDTH < UINT_WIDTH");
+
+unsigned int
+stdc_leading_ones_uc(unsigned char x)
+{
+ const int offset = UINT_WIDTH - UCHAR_WIDTH;
+
+ return (__builtin_clz(~(x << offset)));
+}
+
+/* Avoid triggering undefined behavior if x == 0. */
+static_assert(USHRT_WIDTH < UINT_WIDTH,
+ "stdc_leading_ones_us needs USHRT_WIDTH < UINT_WIDTH");
+
+unsigned int
+stdc_leading_ones_us(unsigned short x)
+{
+ const int offset = UINT_WIDTH - USHRT_WIDTH;
+
+ return (__builtin_clz(~(x << offset)));
+}
+
+unsigned int
+stdc_leading_ones_ui(unsigned int x)
+{
+ if (x == ~0U)
+ return (UINT_WIDTH);
+
+ return (__builtin_clz(~x));
+}
+
+unsigned int
+stdc_leading_ones_ul(unsigned long x)
+{
+ if (x == ~0UL)
+ return (ULONG_WIDTH);
+
+ return (__builtin_clzl(~x));
+}
+
+unsigned int
+stdc_leading_ones_ull(unsigned long long x)
+{
+ if (x == ~0ULL)
+ return (ULLONG_WIDTH);
+
+ return (__builtin_clzll(~x));
+}
diff --git a/lib/libc/stdbit/stdc_leading_zeros.c b/lib/libc/stdbit/stdc_leading_zeros.c
new file mode 100644
index 000000000000..2fdf64ec93d4
--- /dev/null
+++ b/lib/libc/stdbit/stdc_leading_zeros.c
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <assert.h>
+#include <limits.h>
+#include <stdbit.h>
+
+/* Offset must be greater than zero. */
+static_assert(UCHAR_WIDTH < UINT_WIDTH,
+ "stdc_leading_zeros_uc needs UCHAR_WIDTH < UINT_WIDTH");
+
+unsigned int
+stdc_leading_zeros_uc(unsigned char x)
+{
+ const int offset = UINT_WIDTH - UCHAR_WIDTH;
+
+ return (__builtin_clz((x << offset) + (1U << (offset - 1))));
+}
+
+/* Offset must be greater than zero. */
+static_assert(USHRT_WIDTH < UINT_WIDTH,
+ "stdc_leading_zeros_us needs USHRT_WIDTH < UINT_WIDTH");
+
+unsigned int
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