MEMCPY

Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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名前

memcpy - メモリー領域をコピーする。

書式

#include <string.h>

void *memcpy(void *dest, const void *src, size_t n);

説明

memcpy() はメモリー領域 src の先頭 n バイトをメモリー領域 dest にコピーする。コピー元の領域とコピー先の領域が重なってはならない。重なっている場合は memmove(3) を使うこと。

返り値

memcpy() は dest へのポインターを返す。

属性

この節で使用されている用語の説明については、 attributes(7) を参照。

インターフェース	属性	値
memcpy()	Thread safety	MT-Safe

準拠

POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

注意

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 memcpy() with overlapping areas produces undefined behavior.) Most notably, in glibc 2.13 a performance optimization of memcpy() on some platforms (including x86-64) included changing the order in which bytes were copied from src to dest.

This change revealed breakages in a number of applications that performed copying with overlapping areas. 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, a versioned symbol was added so that old binaries (i.e., those linked against glibc versions earlier than 2.14) employed a memcpy() implementation that safely handles the overlapping buffers case (by providing an "older" memcpy() implementation that was aliased to memmove(3)).

この文書について

この man ページは Linux man-pages プロジェクトのリリース 5.10 の一部である。プロジェクトの説明とバグ報告に関する情報は https://www.kernel.org/doc/man-pages/ に書かれている。

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Time: 12:08:36 GMT, June 11, 2022

MEMCPY

名前

書式

説明

返り値

属性

準拠

注意

関連項目

この文書について

関連キーワード

Linux マニュアル 一覧

Index

Linux マニュアル一覧