Index: lib/libc/stdlib/Makefile.inc
===================================================================
--- lib/libc/stdlib/Makefile.inc
+++ lib/libc/stdlib/Makefile.inc
@@ -16,7 +16,7 @@
 	random.c reallocarray.c reallocf.c realpath.c remque.c \
 	set_constraint_handler_s.c strfmon.c strtoimax.c \
 	strtol.c strtold.c strtoll.c strtoq.c strtoul.c strtonum.c strtoull.c \
-        strtoumax.c strtouq.c system.c tdelete.c tfind.c tsearch.c twalk.c
+	strtoumax.c strtouq.c system.c tdelete.c tfind.c tsearch.c twalk.c
 
 # Work around an issue on case-insensitive file systems.
 # libc has both _Exit.c and _exit.s and they both yield
@@ -36,8 +36,9 @@
 	hcreate.3 imaxabs.3 imaxdiv.3 insque.3 labs.3 ldiv.3 llabs.3 lldiv.3 \
 	lsearch.3 memory.3 ptsname.3 qsort.3 \
 	quick_exit.3 \
-	radixsort.3 rand.3 random.3 reallocarray.3 reallocf.3 \
-	realpath.3 strfmon.3 strtod.3 strtol.3 strtonum.3 strtoul.3 system.3 \
+	radixsort.3 rand.3 random.3 reallocarray.3 reallocf.3 realpath.3 \
+	set_constraint_handler_s.3 \
+	strfmon.3 strtod.3 strtol.3 strtonum.3 strtoul.3 system.3 \
 	tsearch.3
 
 MLINKS+=a64l.3 l64a.3 a64l.3 l64a_r.3
@@ -55,6 +56,8 @@
 MLINKS+=random.3 initstate.3 random.3 setstate.3 random.3 srandom.3 \
 	random.3 srandomdev.3
 MLINKS+=radixsort.3 sradixsort.3
+MLINKS+=set_constraint_handler_s.3 abort_handler_s.3
+MLINKS+=set_constraint_handler_s.3 ignore_handler_s.3
 MLINKS+=strfmon.3 strfmon_l.3
 MLINKS+=strtod.3 strtof.3 strtod.3 strtold.3
 MLINKS+=strtol.3 strtoll.3 strtol.3 strtoq.3 strtol.3 strtoimax.3
Index: lib/libc/stdlib/set_constraint_handler_s.3
===================================================================
--- /dev/null
+++ lib/libc/stdlib/set_constraint_handler_s.3
@@ -0,0 +1,140 @@
+.\" Copyright 2018 Nexenta Systems, Inc.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd August 18, 2018
+.Dt SET_CONSTRAINT_HANDLER_S 3
+.Os
+.Sh NAME
+.Nm set_constraint_handler_s ,
+.Nm abort_handler_s ,
+.Nm ignore_handler_s
+.Nd runtime-constraint handling
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.Fd #define __STDC_WANT_LIB_EXT1__ 1
+.In stdlib.h
+.Ft constraint_handler_t
+.Fo set_constraint_handler_s
+.Fa "constraint_handler_t handler"
+.Fc
+.Ft void
+.Fo abort_handler_s
+.Fa "const char *restrict msg"
+.Fa "void *restrict ptr"
+.Fa "errno_t error"
+.Fc
+.Ft void
+.Fo ignore_handler_s
+.Fa "const char *restrict msg"
+.Fa "void *restrict ptr"
+.Fa "errno_t error"
+.Fc
+.Sh DESCRIPTION
+The
+.Fn set_constraint_handler_s
+function sets the runtime-constraint handler to be
+.Fa handler .
+.Pp
+The runtime-constraint handler is the callback function invoked when a library
+function detects a runtime-constraint violation, having the following prototype:
+.Bd -literal
+void (*constraint_handler_t)(const char *restrict msg,
+    void *restrict ptr, errno_t error);
+.Ed
+.Pp
+The arguments are as follows:
+.Bl -tag -width "error"
+.It Fa msg
+A pointer to a character string describing the runtime-constraint violation.
+.It Fa ptr
+A
+.Dv NULL
+pointer.
+.It Fa error
+If the function calling the handler has a return type declared as
+.Vt errno_t ,
+the return value of the function is passed.
+Otherwise, a positive value of type
+.Vt errno_t
+is passed.
+.El
+.Pp
+Only the most recent handler registered with
+.Fn set_constraint_handler_s
+is called when a runtime-constraint violation occurs.
+.Pp
+The implementation has a default constraint handler that is used if no calls to
+the
+.Fn set_constraint_handler_s
+function have been made.
+If the
+.Fa handler
+argument to
+.Fn set_constraint_handler_s
+is a
+.Dv NULL
+pointer, the default handler becomes the current constraint handler.
+.Pp
+The
+.Fn abort_handler_s
+and
+.Fn ignore_handler_s
+are the standard-defined runtime-constraint handlers provided by the C library.
+.Pp
+The
+.Fn abort_handler_s
+function writes the error message including the
+.Fa msg
+to
+.Dv stderr
+and calls the
+.Xr abort 3
+function.
+The
+.Fn abort_handler_s
+is currently the default runtime-constraint handler.
+.Pp
+The
+.Fn ignore_handler_s
+simply returns to its caller.
+.Sh RETURN VALUES
+The
+.Fn set_constraint_handler_s
+function returns a pointer to the previously registered handler, or
+.Dv NULL
+if none was previously registered.
+.Pp
+The
+.Fn abort_handler_s
+function does not return to its caller.
+.Pp
+The
+.Fn ignore_handler_s
+function returns no value.
+.Sh STANDARDS
+The
+.Fn set_constraint_handler_s
+function conforms to
+.St -isoC-2011
+K.3.6.1.1.
Index: lib/libc/string/memset.3
===================================================================
--- lib/libc/string/memset.3
+++ lib/libc/string/memset.3
@@ -32,7 +32,7 @@
 .\"     @(#)memset.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd February 15, 2018
+.Dd August 19, 2018
 .Dt MEMSET 3
 .Os
 .Sh NAME
@@ -44,6 +44,7 @@
 .In string.h
 .Ft void *
 .Fn memset "void *dest" "int c" "size_t len"
+.Fd #define __STDC_WANT_LIB_EXT1__ 1
 .Ft errno_t
 .Fn memset_s "void *dest" "rsize_t destsz" "int c" "rsize_t len"
 .Sh DESCRIPTION
@@ -82,7 +83,6 @@
 is greater than
 .Dv RSIZE_MAX ,
 or
-.Sp
 .Fa len
 is greater than
 .Fa destsz
@@ -93,10 +93,10 @@
 .Xr explicit_bzero 3 ,
 .Fn memset_s
 is not removed through Dead Store Elimination (DSE), making it useful for
-clearing sensitve data.
+clearing sensitive data.
 In contrast
 .Fn memset
-function 
+function
 may be optimized away if the object modified by the function is not accessed
 again.
 To clear memory that will not subsequently be accessed it is advised to use
@@ -117,6 +117,7 @@
 .Sh SEE ALSO
 .Xr bzero 3 ,
 .Xr explicit_bzero 3 ,
+.Xr set_constraint_handler_s 3 ,
 .Xr swab 3 ,
 .Xr wmemset 3
 .Sh STANDARDS
@@ -126,6 +127,6 @@
 conforms to
 .St -isoC .
 .Fn memset_s
-conforms to:
+conforms to
 .St -isoC-2011
 K.3.7.4.1.