PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       posix_memalign — aligned memory allocation (ADVANCED REALTIME)

SYNOPSIS

       #include <stdlib.h>

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

DESCRIPTION

       The posix_memalign() function shall allocate size bytes aligned on a boundary specified by
       alignment, and shall return a pointer to the allocated memory in  memptr.   The  value  of
       alignment shall be a power of two multiple of sizeof(void *).

       Upon  successful  completion,  the  value  pointed  to  by  memptr  shall be a multiple of
       alignment.

       If the size of the space requested is 0, the behavior is implementation-defined: either  a
       null  pointer  shall  be  returned in memptr, or the behavior shall be as if the size were
       some non-zero value, except that the behavior is undefined if the the  value  returned  in
       memptr is used to access an object.

       The  free()  function  shall  deallocate  memory  that  has  previously  been allocated by
       posix_memalign().

RETURN VALUE

       Upon successful completion, posix_memalign() shall return zero; otherwise, an error number
       shall  be  returned  to indicate the error and the contents of memptr shall either be left
       unmodified or be set to a null pointer.

       If size is 0, either:

        *  posix_memalign() shall not attempt to allocate any space,  in  which  case  either  an
           implementation-defined  error number shall be returned, or zero shall be returned with
           a null pointer returned in memptr, or

        *  posix_memalign() shall attempt to allocate some space and, if the allocation succeeds,
           zero  shall  be  returned  and  a  pointer to the allocated space shall be returned in
           memptr.  The application shall ensure that the  pointer  is  not  used  to  access  an
           object.

ERRORS

       The posix_memalign() function shall fail if:

       EINVAL The  value of the alignment parameter is not a power of two multiple of sizeof(void
              *).

       ENOMEM There is insufficient memory available with the requested alignment.

       The following sections are informative.

EXAMPLES

       The following example shows how applications can obtain consistent behavior  on  error  by
       setting *memptr to be a null pointer before calling posix_memalign().

           void *ptr = NULL;
           ...
           //do some work, which might goto error
           if (posix_memalign(&ptr, align, size))
               goto error;

           //do some more work, which might goto error
           ...
           error:
               free(ptr);
               //more cleanup;

APPLICATION USAGE

       The  posix_memalign()  function is part of the Advisory Information option and need not be
       provided on all implementations.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       free(), malloc()

       The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1-2017,  Standard  for  Information Technology -- Portable Operating System Interface
       (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C)  2018  by
       the  Institute  of  Electrical  and Electronics Engineers, Inc and The Open Group.  In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .