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Document memset_s(3). memset_s(3) is defined in

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C11 standard (ISO/IEC 9899:2011) K.3.7.4.1 The memset_s function
(p: 621-622)

Fix memset(3) portion of the man page by replacing the first argument
(destination) "b" with "dest", which is more descriptive than "b".
This also makes it consistent with the term used in the memset_s()
portion of the man page.

See also http://en.cppreference.com/w/c/string/byte/memset.

Reviewed by:	kib
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D13682
This commit is contained in:
Cy Schubert 2018-02-16 05:48:45 +00:00
parent 0b37d3d90e
commit a4d179eeb6
2 changed files with 63 additions and 3 deletions
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1
lib/libc/string/Makefile.inc
View File

@ -50,6 +50,7 @@ MLINKS+=ffs.3 ffsl.3 \
ffs.3 flsll.3
MLINKS+=index.3 rindex.3
MLINKS+=memchr.3 memrchr.3
MLINKS+=memset.3 memset_s.3
MLINKS+=strcasecmp.3 strncasecmp.3 \
strcasecmp.3 strcasecmp_l.3 \
strcasecmp.3 strncasecmp_l.3

65
lib/libc/string/memset.3
View File

@ -32,7 +32,7 @@
.\" @(#)memset.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dd February 15, 2018
.Dt MEMSET 3
.Os
.Sh NAME
@ -43,7 +43,9 @@
.Sh SYNOPSIS
.In string.h
.Ft void *
.Fn memset "void *b" "int c" "size_t len"
.Fn memset "void *dest" "int c" "size_t len"
.Ft errno_t
.Fn memset_s "void *dest" "rsize_t destsz" "int c" "rsize_t len"
.Sh DESCRIPTION
The
.Fn memset
@ -55,13 +57,66 @@ bytes of value
(converted to an
.Vt "unsigned char" )
to the string
.Fa b .
.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
.Sp
.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 sensitve 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 swab 3 ,
.Xr wmemset 3
.Sh STANDARDS
@ -70,3 +125,7 @@ The
function
conforms to
.St -isoC .
.Fn memset_s
conforms to:
.St -isoC-2011
K.3.7.4.1.