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RedHat 9 (Linux i386) - man page for memalign (redhat section 3)

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

NAME
       posix_memalign, memalign, valloc - Allocate aligned memory

SYNOPSIS
       #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);

DESCRIPTION
       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
       two.

       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
       memalign(sysconf(_SC_PAGESIZE),size).

       For all three routines, the memory is not zeroed.

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

       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.

ERRORS
       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.

NOTES
       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.

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

CONFORMING TO
       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.

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

GNU					    2001-10-11				POSIX_MEMALIGN(3)


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