1 // Protocol Buffers - Google's data interchange format 2 // Copyright 2008 Google Inc. All rights reserved. 3 // https://developers.google.com/protocol-buffers/ 4 // 5 // Redistribution and use in source and binary forms, with or without 6 // modification, are permitted provided that the following conditions are 7 // met: 8 // 9 // * Redistributions of source code must retain the above copyright 10 // notice, this list of conditions and the following disclaimer. 11 // * Redistributions in binary form must reproduce the above 12 // copyright notice, this list of conditions and the following disclaimer 13 // in the documentation and/or other materials provided with the 14 // distribution. 15 // * Neither the name of Google Inc. nor the names of its 16 // contributors may be used to endorse or promote products derived from 17 // this software without specific prior written permission. 18 // 19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31 #ifndef GOOGLE_PROTOBUF_MACROS_H__ 32 #define GOOGLE_PROTOBUF_MACROS_H__ 33 34 #include <google/protobuf/stubs/port.h> 35 36 namespace google { 37 namespace protobuf { 38 39 #undef GOOGLE_DISALLOW_EVIL_CONSTRUCTORS 40 #define GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeName) \ 41 TypeName(const TypeName&); \ 42 void operator=(const TypeName&) 43 44 #undef GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS 45 #define GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ 46 TypeName(); \ 47 TypeName(const TypeName&); \ 48 void operator=(const TypeName&) 49 50 // =================================================================== 51 // from google3/base/basictypes.h 52 53 // The GOOGLE_ARRAYSIZE(arr) macro returns the # of elements in an array arr. 54 // The expression is a compile-time constant, and therefore can be 55 // used in defining new arrays, for example. 56 // 57 // GOOGLE_ARRAYSIZE catches a few type errors. If you see a compiler error 58 // 59 // "warning: division by zero in ..." 60 // 61 // when using GOOGLE_ARRAYSIZE, you are (wrongfully) giving it a pointer. 62 // You should only use GOOGLE_ARRAYSIZE on statically allocated arrays. 63 // 64 // The following comments are on the implementation details, and can 65 // be ignored by the users. 66 // 67 // ARRAYSIZE(arr) works by inspecting sizeof(arr) (the # of bytes in 68 // the array) and sizeof(*(arr)) (the # of bytes in one array 69 // element). If the former is divisible by the latter, perhaps arr is 70 // indeed an array, in which case the division result is the # of 71 // elements in the array. Otherwise, arr cannot possibly be an array, 72 // and we generate a compiler error to prevent the code from 73 // compiling. 74 // 75 // Since the size of bool is implementation-defined, we need to cast 76 // !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final 77 // result has type size_t. 78 // 79 // This macro is not perfect as it wrongfully accepts certain 80 // pointers, namely where the pointer size is divisible by the pointee 81 // size. Since all our code has to go through a 32-bit compiler, 82 // where a pointer is 4 bytes, this means all pointers to a type whose 83 // size is 3 or greater than 4 will be (righteously) rejected. 84 // 85 // Kudos to Jorg Brown for this simple and elegant implementation. 86 87 #undef GOOGLE_ARRAYSIZE 88 #define GOOGLE_ARRAYSIZE(a) \ 89 ((sizeof(a) / sizeof(*(a))) / \ 90 static_cast<size_t>(!(sizeof(a) % sizeof(*(a))))) 91 92 // The COMPILE_ASSERT macro can be used to verify that a compile time 93 // expression is true. For example, you could use it to verify the 94 // size of a static array: 95 // 96 // COMPILE_ASSERT(ARRAYSIZE(content_type_names) == CONTENT_NUM_TYPES, 97 // content_type_names_incorrect_size); 98 // 99 // or to make sure a struct is smaller than a certain size: 100 // 101 // COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); 102 // 103 // The second argument to the macro is the name of the variable. If 104 // the expression is false, most compilers will issue a warning/error 105 // containing the name of the variable. 106 107 namespace internal { 108 109 template <bool> 110 struct CompileAssert { 111 }; 112 113 } // namespace internal 114 115 #undef GOOGLE_COMPILE_ASSERT 116 #if __cplusplus >= 201103L 117 #define GOOGLE_COMPILE_ASSERT(expr, msg) static_assert(expr, #msg) 118 #else 119 #define GOOGLE_COMPILE_ASSERT(expr, msg) \ 120 ::google::protobuf::internal::CompileAssert<(bool(expr))> \ 121 msg[bool(expr) ? 1 : -1]; \ 122 (void)msg 123 // Implementation details of COMPILE_ASSERT: 124 // 125 // - COMPILE_ASSERT works by defining an array type that has -1 126 // elements (and thus is invalid) when the expression is false. 127 // 128 // - The simpler definition 129 // 130 // #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1] 131 // 132 // does not work, as gcc supports variable-length arrays whose sizes 133 // are determined at run-time (this is gcc's extension and not part 134 // of the C++ standard). As a result, gcc fails to reject the 135 // following code with the simple definition: 136 // 137 // int foo; 138 // COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is 139 // // not a compile-time constant. 140 // 141 // - By using the type CompileAssert<(bool(expr))>, we ensures that 142 // expr is a compile-time constant. (Template arguments must be 143 // determined at compile-time.) 144 // 145 // - The outter parentheses in CompileAssert<(bool(expr))> are necessary 146 // to work around a bug in gcc 3.4.4 and 4.0.1. If we had written 147 // 148 // CompileAssert<bool(expr)> 149 // 150 // instead, these compilers will refuse to compile 151 // 152 // COMPILE_ASSERT(5 > 0, some_message); 153 // 154 // (They seem to think the ">" in "5 > 0" marks the end of the 155 // template argument list.) 156 // 157 // - The array size is (bool(expr) ? 1 : -1), instead of simply 158 // 159 // ((expr) ? 1 : -1). 160 // 161 // This is to avoid running into a bug in MS VC 7.1, which 162 // causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1. 163 #endif // __cplusplus >= 201103L 164 165 } // namespace protobuf 166 } // namespace google 167 168 #endif // GOOGLE_PROTOBUF_MACROS_H__ 169