According to POSIX, if the src and dst strings overlap, the behavior

is undefined.  Add a warning to that effect.  OK deraadt@ jmc@

src/lib/libc/string/memccpy.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: memccpy.3,v 1.11 2013/06/05 03:39:23 tedu Exp $
+.\"	$OpenBSD: memccpy.3,v 1.12 2013/09/25 21:49:30 millert Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)memccpy.3	8.1 (Berkeley) 6/9/93
 .\"
-.Dd $Mdocdate: June 5 2013 $
+.Dd $Mdocdate: September 25 2013 $
 .Dt MEMCCPY 3
 .Os
 .Sh NAME
@@ -60,6 +60,12 @@ is returned.
 Otherwise,
 .Fa len
 bytes are copied, and a null pointer is returned.
+.Pp
+If the
+.Fa src
+and
+.Fa dst
+strings overlap, the behavior is undefined.
 .Sh SEE ALSO
 .Xr bcopy 3 ,
 .Xr memcpy 3 ,

src/lib/libc/string/stpcpy.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: stpcpy.3,v 1.3 2013/06/05 03:39:23 tedu Exp $
+.\"	$OpenBSD: stpcpy.3,v 1.4 2013/09/25 21:49:31 millert Exp $
 .\"
 .\" Copyright (c) 1990, 1991 The Regents of the University of California.
 .\" All rights reserved.
@@ -31,7 +31,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: June 5 2013 $
+.Dd $Mdocdate: September 25 2013 $
 .Dt STPCPY 3
 .Os
 .Sh NAME
@@ -77,6 +77,12 @@ if the length of
 .Fa src
 is greater than or equal to
 .Fa len .
+.Pp
+If the
+.Fa src
+and
+.Fa dst
+strings overlap, the behavior is undefined.
 .Sh RETURN VALUES
 The
 .Fn stpcpy

src/lib/libc/string/strcpy.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: strcpy.3,v 1.18 2013/07/17 05:42:11 schwarze Exp $
+.\"	$OpenBSD: strcpy.3,v 1.19 2013/09/25 21:49:31 millert Exp $
 .\"
 .\" Copyright (c) 1990, 1991 The Regents of the University of California.
 .\" All rights reserved.
@@ -31,7 +31,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: July 17 2013 $
+.Dd $Mdocdate: September 25 2013 $
 .Dt STRCPY 3
 .Os
 .Sh NAME
@@ -77,6 +77,12 @@ if the length of
 .Fa src
 is greater than or equal to
 .Fa len .
+.Pp
+If the
+.Fa src
+and
+.Fa dst
+strings overlap, the behavior is undefined.
 .Sh RETURN VALUES
 The
 .Fn strcpy

src/lib/libc/string/strlcpy.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: strlcpy.3,v 1.24 2013/07/16 15:21:11 schwarze Exp $
+.\"	$OpenBSD: strlcpy.3,v 1.25 2013/09/25 21:49:31 millert Exp $
 .\"
 .\" Copyright (c) 1998, 2000 Todd C. Miller <Todd.Miller@courtesan.com>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: July 16 2013 $
+.Dd $Mdocdate: September 25 2013 $
 .Dt STRLCPY 3
 .Os
 .Sh NAME
@@ -80,6 +80,12 @@ as it means that either
 is incorrect or that
 .Fa dst
 is not a proper string).
+.Pp
+If the
+.Fa src
+and
+.Fa dst
+strings overlap, the behavior is undefined.
 .Sh RETURN VALUES
 Besides quibbles over the return type
 .Pf ( Va size_t

src/lib/libc/string/wcscpy.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: wcscpy.3,v 1.3 2013/06/05 03:39:23 tedu Exp $
+.\"	$OpenBSD: wcscpy.3,v 1.4 2013/09/25 21:49:31 millert Exp $
 .\"
 .\" Copyright (c) 1990, 1991 The Regents of the University of California.
 .\" All rights reserved.
@@ -31,7 +31,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: June 5 2013 $
+.Dd $Mdocdate: September 25 2013 $
 .Dt WCSCPY 3
 .Os
 .Sh NAME
@@ -77,6 +77,12 @@ if the length of
 .Fa src
 is greater than or equal to
 .Fa len .
+.Pp
+If the
+.Fa src
+and
+.Fa dst
+strings overlap, the behavior is undefined.
 .Sh RETURN VALUES
 The
 .Fn wcscpy

src/lib/libc/string/wcslcpy.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: wcslcpy.3,v 1.5 2013/07/16 15:21:11 schwarze Exp $
+.\"	$OpenBSD: wcslcpy.3,v 1.6 2013/09/25 21:49:31 millert Exp $
 .\"
 .\" Copyright (c) 1998, 2000 Todd C. Miller <Todd.Miller@courtesan.com>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: July 16 2013 $
+.Dd $Mdocdate: September 25 2013 $
 .Dt WCSLCPY 3
 .Os
 .Sh NAME
@@ -88,6 +88,12 @@ It will append at most
 .Fa size
 \(mi wcslen(dst) \(mi 1 wide characters, terminating the result with a null
 wide character.
+.Pp
+If the
+.Fa src
+and
+.Fa dst
+strings overlap, the behavior is undefined.
 .Sh RETURN VALUES
 The
 .Fn wcslcpy