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-'\" t
-.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.\" References consulted:
-.\" Linux libc source code
-.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
-.\" 386BSD man pages
-.\" Modified Sat Jul 24 18:55:27 1993 by Rik Faith (faith@cs.unc.edu)
-.TH memcmp 3 (date) "Linux man-pages (unreleased)"
-.SH NAME
-memcmp \- compare memory areas
-.SH LIBRARY
-Standard C library
-.RI ( libc ", " \-lc )
-.SH SYNOPSIS
-.nf
-.B #include <string.h>
-.P
-.BI "int memcmp(const void " s1 [. n "], const void " s2 [. n "], size_t " n );
-.fi
-.SH DESCRIPTION
-The
-.BR memcmp ()
-function compares the first \fIn\fP bytes (each interpreted as
-.IR "unsigned char" )
-of the memory areas \fIs1\fP and \fIs2\fP.
-.SH RETURN VALUE
-The
-.BR memcmp ()
-function returns an integer less than, equal to, or
-greater than zero if the first \fIn\fP bytes of \fIs1\fP is found,
-respectively, to be less than, to match, or be greater than the first
-\fIn\fP bytes of \fIs2\fP.
-.P
-For a nonzero return value, the sign is determined by the sign of
-the difference between the first pair of bytes (interpreted as
-.IR "unsigned char" )
-that differ in
-.I s1
-and
-.IR s2 .
-.P
-If
-.I n
-is zero, the return value is zero.
-.SH ATTRIBUTES
-For an explanation of the terms used in this section, see
-.BR attributes (7).
-.TS
-allbox;
-lbx lb lb
-l l l.
-Interface Attribute Value
-T{
-.na
-.nh
-.BR memcmp ()
-T} Thread safety MT-Safe
-.TE
-.SH STANDARDS
-C11, POSIX.1-2008.
-.SH HISTORY
-POSIX.1-2001, C89, SVr4, 4.3BSD.
-.SH CAVEATS
-Do not use
-.BR memcmp ()
-to compare confidential data,
-such as cryptographic secrets,
-because the CPU time required for the comparison
-depends on the contents of the addresses compared,
-this function is subject to timing-based side-channel attacks.
-In such cases,
-a function that performs comparisons in deterministic time,
-depending only on
-.I n
-(the quantity of bytes compared)
-is required.
-Some operating systems provide such a function (e.g., NetBSD's
-.BR consttime_memequal ()),
-but no such function is specified in POSIX.
-On Linux, you may need to implement such a function yourself.
-.SH SEE ALSO
-.BR bstring (3),
-.BR strcasecmp (3),
-.BR strcmp (3),
-.BR strcoll (3),
-.BR strncasecmp (3),
-.BR strncmp (3),
-.BR wmemcmp (3)