diff options
Diffstat (limited to 'upstream/opensuse-tumbleweed/man3/memcpy.3')
| -rw-r--r-- | upstream/opensuse-tumbleweed/man3/memcpy.3 | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/upstream/opensuse-tumbleweed/man3/memcpy.3 b/upstream/opensuse-tumbleweed/man3/memcpy.3 new file mode 100644 index 00000000..ec8e3b42 --- /dev/null +++ b/upstream/opensuse-tumbleweed/man3/memcpy.3 @@ -0,0 +1,107 @@ +'\" 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 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +memcpy \- copy memory area +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <string.h> +.PP +.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 +.sp 1 +.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 . +.PP +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) |