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



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

NNAAMMEE
       posix_memalign -- aligned memory allocation (AADDVVAANNCCEEDD RREEAALLTTIIMMEE)

SSYYNNOOPPSSIISS
       #include <stdlib.h>

       int posix_memalign(void **_m_e_m_p_t_r, size_t _a_l_i_g_n_m_e_n_t, size_t _s_i_z_e);

DDEESSCCRRIIPPTTIIOONN
       The _p_o_s_i_x___m_e_m_a_l_i_g_n() function shall allocate _s_i_z_e bytes aligned on a
       boundary specified by _a_l_i_g_n_m_e_n_t, and shall return a pointer to the
       allocated memory in _m_e_m_p_t_r.  The value of _a_l_i_g_n_m_e_n_t shall be a power of
       two multiple of _s_i_z_e_o_f(vvooiidd **).

       Upon successful completion, the value pointed to by _m_e_m_p_t_r shall be a
       multiple of _a_l_i_g_n_m_e_n_t.

       If the size of the space requested is 0, the behavior is
       implementation-defined: either a null pointer shall be returned in
       _m_e_m_p_t_r, 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 _m_e_m_p_t_r is used to access an object.

       The _f_r_e_e() function shall deallocate memory that has previously been
       allocated by _p_o_s_i_x___m_e_m_a_l_i_g_n().

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

       If _s_i_z_e is 0, either:

        *  _p_o_s_i_x___m_e_m_a_l_i_g_n() 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
           _m_e_m_p_t_r, or

        *  _p_o_s_i_x___m_e_m_a_l_i_g_n() 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 _m_e_m_p_t_r.  The application shall
           ensure that the pointer is not used to access an object.

EERRRROORRSS
       The _p_o_s_i_x___m_e_m_a_l_i_g_n() function shall fail if:

       EEIINNVVAALL The value of the alignment parameter is not a power of two
              multiple of _s_i_z_e_o_f(vvooiidd **).

       EENNOOMMEEMM There is insufficient memory available with the requested
              alignment.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

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


           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;

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

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _f_r_e_e(), _m_a_l_l_o_c()

       The Base Definitions volume of POSIX.1-2017, <<ssttddlliibb..hh>>

CCOOPPYYRRIIGGHHTT
       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 .



IEEE/The Open Group                  2017                    POSIX_MEMALIGN(3)
