.\" .\" Copyright (c) 2012 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Alan Barrett .\" .\" 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. .\" .\" $NetBSD$ .\" .Dd February 21, 2012 .Dt MEMSET_S 3 .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 .Fn memset_s "void *s" "rsize_t smax" "int c" "rsize_t n" .Sh DESCRIPTION The .Fn memset_s function copies the value .Fa c (converted to an unsigned char) into each of the first .Fa n bytes of the memory buffer whose starting address is given by .Fa s . .Pp It is a runtime-consrtaints violation if .Fa s is a null pointer, or if either of .Fa smax or .Fa n is larger than .Dv RSIZE_MAX , or if .Fa smax is smaller than .Fa n . If there is a runtime-constraints violation, and if .Fa s is not a null pointer, and if .Fa smax is not larger than .Dv RSIZE_MAX , then, before reporting the runtime-constraints violation, .Fn memset_s copies .Fa smax bytes to the destination. .Pp In contrast to the .Xr memset 3 function, calls to .Fn memset_s will never be .Dq optimised away by a compiler. This property is required by the following sentences in section K.3.7.4.1 of .St -isoC-2011 : .Bd -filled -offset indent Unlike .Fn memset , any call to the .Fn memset_s function shall be evaluated strictly according to the rules of the abstract machine as described in (5.1.2.3). That is, any call to the .Fn memset_s function shall assume that the memory indicated by .Fa s and .Fa n may be accessible in the future and thus must contain the values indicated by .Fa c . .Ed .Sh RETURN VALUES The .Fn memset_s function returns zero for success, or a non-zero error code if there was a runtime-constraints violation. .Sh ERRORS .Fn memset_s returns the following error codes. It does not store the error code in the global .Va errno variable: .Bl -tag -width Er .It Bq Er EINVAL The .Fa s argument was a null pointer. .It Bq Er E2BIG One or both of .Fa smax or .Fa n was larger than .Dv RSIZE_MAX . .It Bq Er EOVERFLOW .Fa n was larger than .Fa smax . .El . .Sh SEE ALSO .Xr memset 3 . .Sh STANDARDS The .Fn memset_s function conforms to .St -isoC-2011 , except that the .Fn set_constraint_handler_s interface is not supported.