diff options
Diffstat (limited to 'lib/libc/string/memset.3')
| -rw-r--r-- | lib/libc/string/memset.3 | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/lib/libc/string/memset.3 b/lib/libc/string/memset.3 new file mode 100644 index 0000000000000..590bc08531b92 --- /dev/null +++ b/lib/libc/string/memset.3 @@ -0,0 +1,132 @@ +.\" Copyright (c) 1990, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" This code is derived from software contributed to Berkeley by +.\" Chris Torek and the American National Standards Committee X3, +.\" on Information Processing Systems. +.\" +.\" 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. +.\" 3. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" 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. +.\" +.\" @(#)memset.3 8.1 (Berkeley) 6/4/93 +.\" $FreeBSD$ +.\" +.Dd August 19, 2018 +.Dt MEMSET 3 +.Os +.Sh NAME +.Nm memset +.Nd write a byte to byte string +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.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 +The +.Fn memset +function +writes +.Fa len +bytes of value +.Fa c +(converted to an +.Vt "unsigned char" ) +to the string +.Fa dest . +Undefined behaviour from +.Fn memset , +resulting from storage overflow, will occur if +.Fa len +is greater than the the length of buffer +.Fa dest . +The behaviour is also undefined if +.Fa dest +is an invalid pointer. +.Pp +The +.Fn memset_s +function behaves the same as +.Fn memset +except that an error is returned and the currently registered +runtime-constraint handler is called if +.Fa dest +is a null pointer, +.Fa destsz +or +.Fa len +is greater than +.Dv RSIZE_MAX , +or +.Fa len +is greater than +.Fa destsz +(buffer overflow would occur). +The runtime-constraint handler is called first and may not return. +If it does return, an error is returned to the caller. +Like +.Xr explicit_bzero 3 , +.Fn memset_s +is not removed through Dead Store Elimination (DSE), making it useful for +clearing sensitive data. +In contrast +.Fn memset +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 +.Fn memset_s +instead of +.Fn memset . +For instance, a buffer containing a password should be cleared with +.Fn memset_s +before +.Xr free 3 . +.Sh RETURN VALUES +The +.Fn memset +function returns its first argument. +The +.Fn memset_s +function returns zero on success, non-zero on error. +.Sh SEE ALSO +.Xr bzero 3 , +.Xr explicit_bzero 3 , +.Xr set_constraint_handler_s 3 , +.Xr swab 3 , +.Xr wmemset 3 +.Sh STANDARDS +The +.Fn memset +function +conforms to +.St -isoC . +.Fn memset_s +conforms to +.St -isoC-2011 +K.3.7.4.1. |