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| author | Alejandro Colomar <alx@kernel.org> | 2024-04-26 15:06:49 +0200 |
|---|---|---|
| committer | Alejandro Colomar <alx@kernel.org> | 2024-05-02 01:24:19 +0200 |
| commit | dcde2f70372b49ec43efc5db864c9ff585d0a2dd (patch) | |
| tree | 78b9b7425130e4a5858e4c01a524d802423879ed /man/man3/memcpy.3 | |
| parent | 12aca537ce78a41bbcdaf485209691e10f8002d7 (diff) | |
| download | man-pages-dcde2f70372b49ec43efc5db864c9ff585d0a2dd.tar.gz | |
man/, share/mk/: Move man*/ to man/
This is a scripted change:
$ mkdir man/;
$ mv man* man/;
$ ln -st . man/man*;
$ find share/mk/ -type f \
| xargs grep -l '^MANDIR *:=' \
| xargs sed -i '/^MANDIR *:=/s,$,/man,';
$ find share/mk/dist/ -type f \
| xargs grep -l man \
| xargs sed -i 's,man%,man/%,g';
Link: <https://lore.kernel.org/linux-man/YxcV4h+Xn7cd6+q2@pevik/T/>
Cc: Petr Vorel <pvorel@suse.cz>
Cc: Jakub Wilk <jwilk@jwilk.net>
Cc: Stefan Puiu <stefan.puiu@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Diffstat (limited to 'man/man3/memcpy.3')
| -rw-r--r-- | man/man3/memcpy.3 | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/man/man3/memcpy.3 b/man/man3/memcpy.3 new file mode 100644 index 0000000000..c97f6701a7 --- /dev/null +++ b/man/man3/memcpy.3 @@ -0,0 +1,106 @@ +'\" t +.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) +.\" and Copyright 2015 Michael Kerrisk <mtk.manpages@gmail.com> +.\" +.\" 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 Sun Jul 25 10:41:09 1993 by Rik Faith (faith@cs.unc.edu) +.TH memcpy 3 (date) "Linux man-pages (unreleased)" +.SH NAME +memcpy \- copy memory area +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <string.h> +.P +.BI "void *memcpy(void " dest "[restrict ." n "], const void " src "[restrict ." n ], +.BI " size_t " n ); +.fi +.SH DESCRIPTION +The +.BR memcpy () +function copies \fIn\fP bytes from memory area +\fIsrc\fP to memory area \fIdest\fP. +The memory areas must not overlap. +Use +.BR memmove (3) +if the memory areas do overlap. +.SH RETURN VALUE +The +.BR memcpy () +function returns a pointer to \fIdest\fP. +.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 memcpy () +T} Thread safety MT-Safe +.TE +.SH STANDARDS +C11, POSIX.1-2008. +.SH HISTORY +POSIX.1-2001, C89, SVr4, 4.3BSD. +.SH CAVEATS +Failure to observe the requirement that the memory areas +do not overlap has been the source of significant bugs. +(POSIX and the C standards are explicit that employing +.BR memcpy () +with overlapping areas produces undefined behavior.) +Most notably, in glibc 2.13 +.\" glibc commit 6fb8cbcb58a29fff73eb2101b34caa19a7f88eba +a performance optimization of +.BR memcpy () +on some platforms (including x86-64) included changing the order +.\" From forward copying to backward copying +in which bytes were copied from +.I src +to +.IR dest . +.P +This change revealed breakages in a number of applications that performed +copying with overlapping areas. +.\" Adobe Flash player was the highest profile example: +.\" https://bugzilla.redhat.com/show_bug.cgi?id=638477 +.\" Reported: 2010-09-29 02:35 EDT by JCHuynh +.\" Bug 638477 - Strange sound on mp3 flash website +.\" +.\" https://sourceware.org/bugzilla/show_bug.cgi?id=12518 +.\" Bug 12518 - memcpy acts randomly (and differently) with overlapping areas +.\" Reported: 2011-02-25 02:26 UTC by Linus Torvalds +.\" +Under the previous implementation, +the order in which the bytes were copied had fortuitously hidden the bug, +which was revealed when the copying order was reversed. +In glibc 2.14, +.\" glibc commit 0354e355014b7bfda32622e0255399d859862fcd +a versioned symbol was added so that old binaries +(i.e., those linked against glibc versions earlier than 2.14) +employed a +.BR memcpy () +implementation that safely handles the overlapping buffers case +(by providing an "older" +.BR memcpy () +implementation that was aliased to +.BR memmove (3)). +.SH SEE ALSO +.BR bcopy (3), +.BR bstring (3), +.BR memccpy (3), +.BR memmove (3), +.BR mempcpy (3), +.BR strcpy (3), +.BR strncpy (3), +.BR wmemcpy (3) |