Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

POSIX_MEMALIGN(3)          Library Functions Manual          POSIX_MEMALIGN(3)

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 9899:2018
     ("ISO C18").

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

NetBSD 10.99                     July 27, 2018                    NetBSD 10.99