NAME¶

posix_memalign - allocate aligned memory

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <stdlib.h>

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

posix_memalign():

    _POSIX_C_SOURCE >= 200112L

DESCRIPTION¶

posix_memalign() allocates size bytes and places the address of the allocated memory in *memptr. The address of the allocated memory will be a multiple of alignment, which must be a power of two and a multiple of sizeof(void *). This address can later be successfully passed to free(3). If size is 0, then the value placed in *memptr is either NULL or a unique pointer value.

The memory is not zeroed.

aligned_alloc(3) is a standard function that provides the same functionality, and has a more ergonomic prototype. Use that instead.

RETURN VALUE¶

posix_memalign() returns zero on success, or one of the error values listed in the next section on failure. The value of errno is not set.

ERRORS¶

EINVAL

The alignment argument was not a power of two, or was not a multiple of sizeof(void *).

ENOMEM

Out of memory.

ATTRIBUTES¶

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

STANDARDS¶

POSIX.1-2024.

HISTORY¶

glibc 2.1.91. POSIX.1d, POSIX.1-2001.

CAVEATS¶

On Linux (and other systems), posix_memalign() does not modify memptr on failure. A requirement standardizing this behavior was added in POSIX.1-2008 TC2.

SEE ALSO¶

aligned_alloc(3)