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      1 /*
      2 
      3 Copyright (C) 2010 Apple Inc. All rights reserved.
      4 
      5 Redistribution and use in source and binary forms, with or without
      6 modification, are permitted provided that the following conditions
      7 are met:
      8 1.  Redistributions of source code must retain the above copyright
      9     notice, this list of conditions and the following disclaimer.
     10 2.  Redistributions in binary form must reproduce the above copyright
     11     notice, this list of conditions and the following disclaimer in the
     12     documentation and/or other materials provided with the distribution.
     13 
     14 THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
     15 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     16 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     17 DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     18 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     19 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     20 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
     21 ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     23 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24 
     25 */
     26 
     27 #ifndef NullPtr_h
     28 #define NullPtr_h
     29 
     30 // For compilers and standard libraries that do not yet include it, this adds the
     31 // nullptr_t type and nullptr object. They are defined in the same namespaces they
     32 // would be in compiler and library that had the support.
     33 
     34 #if COMPILER_SUPPORTS(CXX_NULLPTR) || defined(_LIBCPP_VERSION)
     35 
     36 // libstdc++ supports nullptr_t starting with gcc 4.6. STLport doesn't define it.
     37 #if (defined(__GLIBCXX__) && __GLIBCXX__ < 20110325) || defined(_STLPORT_VERSION)
     38 namespace std {
     39 typedef decltype(nullptr) nullptr_t;
     40 }
     41 #endif
     42 
     43 #else
     44 
     45 #include "wtf/WTFExport.h"
     46 
     47 namespace std {
     48 class nullptr_t {
     49 public:
     50     // Required in order to create const nullptr_t objects without an
     51     // explicit initializer in GCC 4.5, a la:
     52     //
     53     // const std::nullptr_t nullptr;
     54     nullptr_t() { }
     55 
     56     // Make nullptr convertible to any pointer type.
     57     template<typename T> operator T*() const { return 0; }
     58     // Make nullptr convertible to any member pointer type.
     59     template<typename C, typename T> operator T C::*() { return 0; }
     60 private:
     61     // Do not allow taking the address of nullptr.
     62     void operator&();
     63 };
     64 }
     65 WTF_EXPORT extern const std::nullptr_t nullptr;
     66 
     67 #endif
     68 
     69 #if COMPILER_SUPPORTS(CXX_DELETED_FUNCTIONS)
     70 #define WTF_DISALLOW_CONSTRUCTION_FROM_ZERO(ClassName) \
     71     private: \
     72         ClassName(int) = delete
     73 #define WTF_DISALLOW_ZERO_ASSIGNMENT(ClassName) \
     74     private: \
     75         ClassName& operator=(int) = delete
     76 #else
     77 #define WTF_DISALLOW_CONSTRUCTION_FROM_ZERO(ClassName) \
     78     private: \
     79         ClassName(int)
     80 #define WTF_DISALLOW_ZERO_ASSIGNMENT(ClassName) \
     81     private: \
     82         ClassName& operator=(int)
     83 #endif
     84 
     85 #endif
     86