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   memcpy    ( 3 )

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Имя (Name)

memcpy - copy memory area

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Синопсис (Synopsis)

#include <string.h>

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

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Описание (Description)

The memcpy() function copies n bytes from memory area src to
       memory area dest.  The memory areas must not overlap.  Use
       memmove(3) if the memory areas do overlap.

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Возвращаемое значение (Return value)

The memcpy() function returns a pointer to dest.

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Атрибуты (Attributes)

For an explanation of the terms used in this section, see
       attributes(7).

       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │Interface                             │ Attribute     │ Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │memcpy()                              │ Thread safety │ MT-Safe │
       └──────────────────────────────────────┴───────────────┴─────────┘

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Стандарты (Conforming to)

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

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Примечание (Note)

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)).

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Смотри также (See also)

bcopy(3), bstring(3), memccpy(3), memmove(3), mempcpy(3),
       strcpy(3), strncpy(3), wmemcpy(3)

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