mfbt/NullPtr.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 /*
   7  * Implements a workaround for compilers which do not support the C++11 nullptr
   8  * constant.
   9  */
  10
  11 #ifndef mozilla_NullPtr_h_
  12 #define mozilla_NullPtr_h_
  13
  14 #include "mozilla/Compiler.h"
  15
  16 #if defined(__clang__)
  17 #  ifndef __has_extension
  18 #    define __has_extension __has_feature
  19 #  endif
  20 #  if __has_extension(cxx_nullptr)
  21 #    define MOZ_HAVE_CXX11_NULLPTR
  22 #  endif
  23 #elif defined(__GNUC__)
  24 #  if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
  25 #    if MOZ_GCC_VERSION_AT_LEAST(4, 6, 0)
  26 #      define MOZ_HAVE_CXX11_NULLPTR
  27 #    endif
  28 #  endif
  29 #elif _MSC_VER >= 1600
  30 # define MOZ_HAVE_CXX11_NULLPTR
  31 #endif
  32
  33 /**
  34  * Use C++11 nullptr if available; otherwise use __null for gcc, or a 0 literal
  35  * with the correct size to match the size of a pointer on a given platform.
  36  */
  37
  38 #ifndef MOZ_HAVE_CXX11_NULLPTR
  39 #  if defined(__GNUC__)
  40 #    define nullptr __null
  41 #  elif defined(_WIN64)
  42 #    define nullptr 0LL
  43 #  else
  44 #    define nullptr 0L
  45 #  endif
  46 #endif
  47
  48 #endif  /* mozilla_NullPtr_h_ */