NAME

posix_memalign, aligned_alloc — aligned memory allocation

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <stdlib.h>

int
posix_memalign(void **ptr, size_t alignment, size_t size);

void *
aligned_alloc(size_t alignment, size_t size);

DESCRIPTION

The posix_memalign() function allocates size bytes of memory such that the allocation's base address is an even multiple of alignment, and returns the allocation in the value pointed to by ptr. The requested alignment must be a power of 2 at least as large as sizeof(void *).

The aligned_alloc() function allocates size bytes of memory such that the allocation's base address is an even multiple of alignment. The requested alignment must be a power of 2.

Memory that is allocated via posix_memalign() or aligned_alloc() can be used as an argument in subsequent calls to realloc(3) and free(3).

RETURN VALUES

The posix_memalign() function returns the value 0 if successful; otherwise it returns an error value.

The aligned_alloc() function returns a pointer to the allocated memory if successful; on failure it returns NULL and sets errno to indicate the error.

ERRORS

The posix_memalign() and aligned_alloc() functions will fail if:

[EINVAL]

The alignment parameter is not a power of 2.

[ENOMEM]

Memory allocation error.

The posix_memalign() function will also fail if

[EINVAL]

The alignment parameter is not at least as large as sizeof(void *).

SEE ALSO

free(3), malloc(3), realloc(3), valloc(3)

STANDARDS

The posix_memalign() function conforms to IEEE Std 1003.1-2001 (“POSIX.1”). The aligned_alloc() function conforms to ISO/IEC 9899:2011 (“ISO C11”).

HISTORY

ISO/IEC 9899:2011 (“ISO C11”) required size to be an integer multiple of alignment. This requirement was removed in later standards.