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@

include/strings.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: strings.h,v 1.6 2017/09/10 21:50:36 schwarze Exp $	*/
+/*	$OpenBSD: strings.h,v 1.7 2025/10/24 11:30:06 claudio Exp $	*/
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
@@ -78,6 +78,10 @@ int	 strncasecmp(const char *, const char *, size_t);
 int	 strcasecmp_l(const char *, const char *, locale_t);
 int	 strncasecmp_l(const char *, const char *, size_t, locale_t);
 #endif
+#if __POSIX_VISIBLE >= 202405
+int	 ffsl(long);
+int	 ffsll(long long);
+#endif
 __END_DECLS
 
 #endif /* _STRINGS_H_ */

lib/libc/Symbols.list

@@ -1608,6 +1608,8 @@ bcopy
 bzero
 explicit_bzero
 ffs
+ffsl
+ffsll
 index
 memccpy
 memchr

lib/libc/shlib_version

@@ -1,4 +1,4 @@
 major=102
-minor=0
+minor=1
 # note: If changes were made to include/thread_private.h or if system calls
 # were added/changed then librthread/shlib_version must also be updated.

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 \

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 .

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);
+}

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);
+}