#include <string.h>
void *memcpy(void dest[restrict .n], const void src[restrict .n],
size_t n); memcpy() 함수는 메모리 영역 src에서 메모리 영역 dest로 n 바이트를 복사한다. 메모리 영역은 겹쳐지지 않는다. 만일 메모리 영역을 겹쳐 쓰길 원한다면 memmove(3)EN를 사용해라.
memcpy() 함수는 포인터 dest를 반환한다.
이 섹션에서 사용되는 용어에 대한 설명은 attributes(7)EN을 참조하십시오.
| 상호 작용 | 속성 | 번호 |
| memcpy() | Thread safety | MT-Safe |
POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.
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)EN).