extl/utility/offset_of.h

   1 /* ///////////////////////////////////////////////////////////////////////
   2  * File:                offsetof.h
   3  *
   4  * Created:             08.02.22
   5  * Updated:             08.05.05
   6  *
   7  * Brief: The offset of a given member within a class, struct or union type
   8  *
   9  * [<Home>]
  10  * Copyright (c) 2008-2020, Waruqi All rights reserved.
  11  * //////////////////////////////////////////////////////////////////// */
  12
  13 #ifndef EXTL_UTILITY_OFFSET_OF_H
  14 #define EXTL_UTILITY_OFFSET_OF_H
  15
  16 /*!\file offsetof.h
  17  * \brief The offset of a given member within a class, struct or union type
  18  */
  19
  20 /* ///////////////////////////////////////////////////////////////////////
  21  * Includes
  22  */
  23 #include "../config/config.h"
  24
  25 /* ///////////////////////////////////////////////////////////////////////
  26  * Macros
  27  */
  28 #ifdef EXTL_OFFSET_OF
  29 #       undef EXTL_OFFSET_OF
  30 #endif
  31
  32 #ifdef __cplusplus
  33 /* GCC warning: invalid access to non-static data member of NULL object */
  34 #       if defined(EXTL_COMPILER_IS_GCC)
  35 #               define EXTL_OFFSET_OF(S, M)     \
  36                         (reinterpret_cast< EXTL_NS(e_size_t) >(&reinterpret_cast<S*>(1)->M) - 1)
  37 #       else
  38 #               define EXTL_OFFSET_OF(S, M)     \
  39                         (reinterpret_cast< EXTL_NS(e_size_t) >(&reinterpret_cast<S*>(0)->M))
  40 #       endif
  41 #else
  42 #       define EXTL_OFFSET_OF(S, M)     ((e_size_t)&((S*)(0))->M)
  43 #endif
  44
  45 /* ///////////////////////////////////////////////////////////////////////
  46  * Unit-testing
  47  */
  48 #ifdef EXTL_UTILITY_OFFSET_OF_TEST_ENABLE
  49 #       include "unit_test/offset_of_test.h"
  50 #endif
  51
  52 /* //////////////////////////////////////////////////////////////////// */
  53 #endif /* EXTL_UTILITY_OFFSET_OF_H */
  54 /* //////////////////////////////////////////////////////////////////// */