Implement ffsl() and ffsll() using the compiler builtin __builtin_ctzl

now that all archs use at least gcc4.
ffsl() and ffsll() are now part of POSIX.
OK deraadt@, input from miod@ and jsg@

4 files changed, 66 insertions, 11 deletions

diff --git a/src/lib/libc/string/Makefile.inc b/src/lib/libc/string/Makefile.inc
index 204ca1b266..f8b6330453 100644
--- a/src/lib/libc/string/Makefile.inc
+++ b/src/lib/libc/string/Makefile.inc
@@ -1,13 +1,13 @@
-#       $OpenBSD: Makefile.inc,v 1.40 2024/07/14 09:51:18 jca Exp $
+#       $OpenBSD: Makefile.inc,v 1.41 2025/10/24 11:30:06 claudio Exp $
 
 # string sources
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/string ${LIBCSRCDIR}/string
 
-SRCS+=  explicit_bzero.c memccpy.c memmem.c memrchr.c stpcpy.c stpncpy.c \
-        strcasecmp.c strcasecmp_l.c strcasestr.c strcoll.c strcoll_l.c \
-        strdup.c strerror.c strerror_l.c strerror_r.c strmode.c \
-        strndup.c strnlen.c strsignal.c strtok.c strxfrm.c strxfrm_l.c \
-        timingsafe_bcmp.c timingsafe_memcmp.c \
+SRCS+=  explicit_bzero.c ffsl.c ffsll.c memccpy.c memmem.c memrchr.c \
+        stpcpy.c stpncpy.c strcasecmp.c strcasecmp_l.c strcasestr.c \
+        strcoll.c strcoll_l.c strdup.c strerror.c strerror_l.c strerror_r.c \
+        strmode.c strndup.c strnlen.c strsignal.c strtok.c strxfrm.c \
+        strxfrm_l.c timingsafe_bcmp.c timingsafe_memcmp.c \
         wcscat.c wcschr.c wcscmp.c wcscpy.c wcscspn.c wcslcat.c wcslcpy.c \
         wcslen.c wcsncat.c wcsncmp.c wcsncpy.c wcsnlen.c wcspbrk.c wcsrchr.c \
         wcsspn.c wcsstr.c wcstok.c wcswcs.c wcswidth.c wmemchr.c wmemcmp.c \
diff --git a/src/lib/libc/string/ffs.3 b/src/lib/libc/string/ffs.3
index e78ab99e8f..630db1c584 100644
--- a/src/lib/libc/string/ffs.3
+++ b/src/lib/libc/string/ffs.3
@@ -27,22 +27,31 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"     $OpenBSD: ffs.3,v 1.11 2019/08/30 18:35:03 deraadt Exp $
+.\"     $OpenBSD: ffs.3,v 1.12 2025/10/24 11:30:06 claudio Exp $
 .\"
-.Dd $Mdocdate: August 30 2019 $
+.Dd $Mdocdate: October 24 2025 $
 .Dt FFS 3
 .Os
 .Sh NAME
-.Nm ffs
+.Nm ffs ,
+.Nm ffsl ,
+.Nm ffsll
 .Nd find first bit set in a bit string
 .Sh SYNOPSIS
 .In strings.h
 .Ft int
 .Fn ffs "int value"
+.Ft int
+.Fn ffsl "long value"
+.Ft int
+.Fn ffsll "long long value"
 .Sh DESCRIPTION
 The
-.Fn ffs
-function finds the first bit set in
+.Fn ffs ,
+.Fn ffsl
+and
+.Fn ffsll
+functions find the first bit set in
 .Fa value
 and returns the index of that bit.
 Bits are numbered starting from 1, starting at the rightmost bit.
@@ -54,8 +63,20 @@ The
 .Fn ffs
 function conforms to
 .St -p1003.1-2008 .
+The
+.Fn ffsl
+and
+.Fn ffsll
+functions conform to
+.St -p1003.1-2024 .
 .Sh HISTORY
 The
 .Fn ffs
 function first appeared in
 .Bx 4.2 .
+The
+.Fn ffsl
+and
+.Fn ffsll
+functions first appeared in
+.Ox 7.9 .
diff --git a/src/lib/libc/string/ffsl.c b/src/lib/libc/string/ffsl.c
new file mode 100644
index 0000000000..182318c3d6
--- /dev/null
+++ b/src/lib/libc/string/ffsl.c
@@ -0,0 +1,17 @@
+/*      $OpenBSD: ffsl.c,v 1.1 2025/10/24 11:30:06 claudio Exp $        */
+
+/*
+ * Public domain.
+ * Written by Claudio Jeker.
+ */
+
+#include <strings.h>
+
+/*
+ * ffs -- find the first (least significant) bit set
+ */
+int
+ffsl(long mask)
+{
+        return (mask ? __builtin_ctzl(mask) + 1 : 0);
+}
diff --git a/src/lib/libc/string/ffsll.c b/src/lib/libc/string/ffsll.c
new file mode 100644
index 0000000000..9370c5ae41
--- /dev/null
+++ b/src/lib/libc/string/ffsll.c
@@ -0,0 +1,17 @@
+/*      $OpenBSD: ffsll.c,v 1.1 2025/10/24 11:30:06 claudio Exp $       */
+
+/*
+ * Public domain.
+ * Written by Claudio Jeker.
+ */
+
+#include <strings.h>
+
+/*
+ * ffs -- find the first (least significant) bit set
+ */
+int
+ffsll(long long mask)
+{
+        return (mask ? __builtin_ctzll(mask) + 1 : 0);
+}