From e0d4f419ac41aa91b862f3ceadc32a86abf08572 Mon Sep 17 00:00:00 2001
From: Robert Clausecker <fuz@FreeBSD.org>
Date: Tue, 5 Dec 2023 09:03:28 -0500
Subject: [PATCH] lib/libc/string: document restrict qualification of memccpy()
 arguments

POSIX.1-2004 and the upcoming C23 agree that memccpy()'s arguments
are restrict qualified and must not overlap.  In 2002, restrict
qualifiers were added to <string.h>'s declaration of the function.
Make things official and document that the arguments must not
overlap.

See also:	61b60edfd3fff20f884419f8097870c7045315c9
Approved by:	kib
MFC after:	1 month
MFC to:		stable/14
---
 lib/libc/string/bstring.3 | 10 ++++++++--
 lib/libc/string/memccpy.3 | 33 ++++++++++++++++++++++++++++++---
 lib/libc/string/memccpy.c |  2 +-
 3 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/lib/libc/string/bstring.3 b/lib/libc/string/bstring.3
index fd976c7676b..91603fe6dba 100644
--- a/lib/libc/string/bstring.3
+++ b/lib/libc/string/bstring.3
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd June 4, 1993
+.Dd December 5, 2023
 .Dt BSTRING 3
 .Os
 .Sh NAME
@@ -56,7 +56,12 @@
 .Ft int
 .Fn memcmp "const void *b1" "const void *b2" "size_t len"
 .Ft void *
-.Fn memccpy "void *dst" "const void *src" "int c" "size_t len"
+.Fo memccpy
+.Fa "void * restrict dst"
+.Fa "const void * restrict src"
+.Fa "int c"
+.Fa "size_t len"
+.Fc
 .Ft void *
 .Fn memcpy "void *dst" "const void *src" "size_t len"
 .Ft void *
@@ -78,6 +83,7 @@ See the specific manual pages for more information.
 .Xr memccpy 3 ,
 .Xr memchr 3 ,
 .Xr memcmp 3 ,
+.Xr memccpy 3 ,
 .Xr memcpy 3 ,
 .Xr memmove 3 ,
 .Xr memset 3
diff --git a/lib/libc/string/memccpy.3 b/lib/libc/string/memccpy.3
index ce8d5f65ac9..3bdae24354c 100644
--- a/lib/libc/string/memccpy.3
+++ b/lib/libc/string/memccpy.3
@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd June 9, 1993
+.Dd December 5, 2023
 .Dt MEMCCPY 3
 .Os
 .Sh NAME
@@ -36,7 +36,12 @@
 .Sh SYNOPSIS
 .In string.h
 .Ft void *
-.Fn memccpy "void *dst" "const void *src" "int c" "size_t len"
+.Fo memccpy
+.Fa "void * restrict dst"
+.Fa "const void * restrict src"
+.Fa "int c"
+.Fa "size_t len"
+.Fc
 .Sh DESCRIPTION
 The
 .Fn memccpy
@@ -59,13 +64,35 @@ is returned.
 Otherwise,
 .Fa len
 bytes are copied, and a NULL pointer is returned.
+If
+.Fa src
+and
+.Fa dst
+overlap, behavior is undefined.
 .Sh SEE ALSO
 .Xr bcopy 3 ,
 .Xr memcpy 3 ,
 .Xr memmove 3 ,
 .Xr strcpy 3
+.Sh STANDARDS
+The
+.Fn memccpy
+function conforms to
+.St -p1003.1-2004
+and
+.\" St -isoC-2024 .
+ISO/IEC 9899:2024 (\(lqISO\~C23\(rq).
 .Sh HISTORY
 The
 .Fn memccpy
 function first appeared in
-.Bx 4.4 .
+.Bx 4.4
+and was first specified in the
+.\" St -svid1 .
+System\~V Interface Definition, First Edition (\(lqSVID1\(rq).
+The
+.Ft restrict
+keyword was added to the prototype in
+.Fx 5.0.0
+in accordance with the updated specification of
+.St -p1003.1-2004 .
diff --git a/lib/libc/string/memccpy.c b/lib/libc/string/memccpy.c
index 174824ba239..d6a446503eb 100644
--- a/lib/libc/string/memccpy.c
+++ b/lib/libc/string/memccpy.c
@@ -32,7 +32,7 @@
 #include <string.h>
 
 void *
-memccpy(void *t, const void *f, int c, size_t n)
+memccpy(void * restrict t, const void * restrict f, int c, size_t n)
 {
 
 	if (n) {