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POSIX_MEMALIGN(3)		    Linux Programmer's Manual			POSIX_MEMALIGN(3)

       posix_memalign, memalign, valloc - Allocate aligned memory

       #include <stdlib.h>

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

       The function 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 *).

       The  obsolete  function memalign() allocates size bytes and returns a pointer to the allo-
       cated memory.  The memory address will be a multiple of boundary, which must be a power of

       The obsolete function valloc() allocates size bytes and returns a pointer to the allocated
       memory.	The memory address will be a multiple of the page  size.   It  is  equivalent  to

       For all three routines, the memory is not zeroed.

       memalign() and valloc() return the pointer to the allocated memory, or NULL if the request

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

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

       ENOMEM There was insufficient memory to fulfill the allocation request.

       posix_memalign() verifies that alignment matches the requirements detailed  above.   mema-
       lign() may not check that the boundary parameter is correct.

       POSIX requires that memory obtained from posix_memalign() can be freed using free().  Some
       systems provide no way to reclaim memory allocated with memalign()  or  valloc()  (because
       one  can  only pass to free() a pointer gotten from malloc(), while e.g.  memalign() would
       call malloc() and then align the obtained value).  GNU libc allows  memory  obtained  from
       any of these three routines to be reclaimed with free().

       GNU  libc  malloc()  always returns 8-byte aligned memory addresses, so these routines are
       only needed if you require larger alignment values.

       The functions memalign() and valloc() have been available in  all  Linux  libc  libraries.
       The function posix_memalign() is available since glibc 2.1.91.

       The  function valloc() appeared in 3.0 BSD. It is documented as being obsolete in BSD 4.3,
       and as legacy in SUSv2. It no longer occurs in SUSv3.  The function memalign() appears  in
       SunOS 4.1.3 but not in BSD 4.4.	The function posix_memalign() comes from POSIX 1003.1d.

       malloc(3), free(3), getpagesize(2), brk(2)

GNU					    2001-10-11				POSIX_MEMALIGN(3)
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