stddef.h(3)                POSIX Programmer's Manual               stddef.h(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
       stddef.h -- standard type definitions

SSYYNNOOPPSSIISS
       #include <stddef.h>

DDEESSCCRRIIPPTTIIOONN
       The functionality described on this reference page is aligned with the
       ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2017
       defers to the ISO C standard.

       The _<_s_t_d_d_e_f_._h_> header shall define the following macros:

       NULL      Null pointer constant.  The macro shall expand to an integer
                 constant expression with the value 0 cast to type vvooiidd **.

       offsetof(_t_y_p_e, _m_e_m_b_e_r_-_d_e_s_i_g_n_a_t_o_r)
                 Integer constant expression of type ssiizzee__tt, the value of
                 which is the offset in bytes to the structure member (_m_e_m_b_e_r_-
                 _d_e_s_i_g_n_a_t_o_r), from the beginning of its structure (_t_y_p_e).

       The _<_s_t_d_d_e_f_._h_> header shall define the following types:

       ppttrrddiiffff__tt Signed integer type of the result of subtracting two
                 pointers.

       wwcchhaarr__tt   Integer type whose range of values can represent distinct
                 codes for all members of the largest extended character set
                 specified among the supported locales; the null character
                 shall have the code value zero. Each member of the basic
                 character set shall have a code value equal to its value when
                 used as the lone character in an integer character constant
                 if an implementation does not define
                 __STDC_MB_MIGHT_NEQ_WC__.

       ssiizzee__tt    Unsigned integer type of the result of the _s_i_z_e_o_f operator.

       The implementation shall support one or more programming environments
       in which the widths of ppttrrddiiffff__tt, ssiizzee__tt, and wwcchhaarr__tt are no greater
       than the width of type lloonngg.  The names of these programming
       environments can be obtained using the _c_o_n_f_s_t_r() function or the
       _g_e_t_c_o_n_f utility.

       _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_.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       The ISO C standard does not require the NULL macro to include the cast
       to type vvooiidd ** and specifies that the NULL macro be implementation-
       defined. POSIX.1-2008 requires the cast and therefore need not be
       implementation-defined.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       <<ssyyss__ttyyppeess..hh>>, <<wwcchhaarr..hh>>

       The System Interfaces volume of POSIX.1-2017, _c_o_n_f_s_t_r()

       The Shell and Utilities volume of POSIX.1-2017, _g_e_t_c_o_n_f

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                          stddef.h(3)
