.\"
.\" This file and its contents are supplied under the terms of the
.\" Common Development and Distribution License ("CDDL"), version 1.0.
.\" You may only use this file in accordance with the terms of version
.\" 1.0 of the CDDL.
.\"
.\" A full copy of the text of the CDDL should have accompanied this
.\" source.  A copy of the CDDL is also available via the Internet at
.\" http://www.illumos.org/license/CDDL.
.\"
.\"
.\" Copyright 2018 Nexenta Systems, Inc.
.\"
.Dd August 12, 2017
.Dt MEMSET_S 3C
.Os
.Sh NAME
.Nm memset_s
.Nd copy a value to all bytes of a memory buffer
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #define __STDC_WANT_LIB_EXT1__ 1
.In string.h
.Ft errno_t
.Fo memset_s
.Fa "void *s"
.Fa "rsize_t smax"
.Fa "int c"
.Fa "rsize_t n"
.Fc
.Sh DESCRIPTION
The
.Fn memset_s
function copies the value of
.Fa c
.Po converted to an
.Vt unsigned char
.Pc
into each of the first
.Fa n
bytes of the memory buffer pointed to by
.Fa s .
.Pp
Unlike the
.Xr memset 3C ,
.Fn memset_s
is guaranteed to never be optimized away by the compiler.
.Pp
The
.Fn memset_s
function detects the following runtime-constraint violations:
.Bl -enum
.It
.Fa s
is a
.Dv NULL
pointer.
.It
.Fa smax
or
.Fa n
is greater than
.Dv RSIZE_MAX .
.It
.Fa n
is greater than
.Fa smax
.Pq buffer overflow .
.El
.Pp
If runtime-constraint violation is detected, and if
.Fa s
and
.Fa smax
are valid, the
.Fn memset_s
function copies the value of
.Fa c
.Po converted to an
.Vt unsigned char
.Pc
into each of the first
.Fa smax
bytes of the memory buffer pointed to by
.Fa s
before calling the runtime-constraint handler.
.Sh RETURN VALUES
The
.Fn memset_s
function returns 0 if there was no runtime-constraint violation.
Otherwise, a non-zero value is returned.
.Sh INTERFACE STABILITY
.Sy Standard
.Sh MT-LEVEL
.Sy Safe
.Sh SEE ALSO
.Xr memset 3C ,
.Xr set_constraint_handler 3C
.Sh STANDARDS
The
.Fn memset_s
function conforms to
.St -isoC-2011 .