1 // Copyright 2014 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef V8_BASE_COMPILER_SPECIFIC_H_ 6 #define V8_BASE_COMPILER_SPECIFIC_H_ 7 8 #include "include/v8config.h" 9 10 // Annotate a using ALLOW_UNUSED_TYPE = or function indicating it's ok if it's 11 // not used. Use like: 12 // using Bar = Foo; 13 #if V8_HAS_ATTRIBUTE_UNUSED 14 #define ALLOW_UNUSED_TYPE __attribute__((unused)) 15 #else 16 #define ALLOW_UNUSED_TYPE 17 #endif 18 19 // Tell the compiler a function is using a printf-style format string. 20 // |format_param| is the one-based index of the format string parameter; 21 // |dots_param| is the one-based index of the "..." parameter. 22 // For v*printf functions (which take a va_list), pass 0 for dots_param. 23 // (This is undocumented but matches what the system C headers do.) 24 #if defined(__GNUC__) 25 #define PRINTF_FORMAT(format_param, dots_param) \ 26 __attribute__((format(printf, format_param, dots_param))) 27 #else 28 #define PRINTF_FORMAT(format_param, dots_param) 29 #endif 30 31 // The C++ standard requires that static const members have an out-of-class 32 // definition (in a single compilation unit), but MSVC chokes on this (when 33 // language extensions, which are required, are enabled). (You're only likely to 34 // notice the need for a definition if you take the address of the member or, 35 // more commonly, pass it to a function that takes it as a reference argument -- 36 // probably an STL function.) This macro makes MSVC do the right thing. See 37 // http://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx for more 38 // information. Use like: 39 // 40 // In .h file: 41 // struct Foo { 42 // static const int kBar = 5; 43 // }; 44 // 45 // In .cc file: 46 // STATIC_CONST_MEMBER_DEFINITION const int Foo::kBar; 47 #if V8_HAS_DECLSPEC_SELECTANY 48 #define STATIC_CONST_MEMBER_DEFINITION __declspec(selectany) 49 #else 50 #define STATIC_CONST_MEMBER_DEFINITION 51 #endif 52 53 #if V8_CC_MSVC 54 55 #include <sal.h> 56 57 // Macros for suppressing and disabling warnings on MSVC. 58 // 59 // Warning numbers are enumerated at: 60 // http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx 61 // 62 // The warning pragma: 63 // http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx 64 // 65 // Using __pragma instead of #pragma inside macros: 66 // http://msdn.microsoft.com/en-us/library/d9x1s805.aspx 67 68 // MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and 69 // for the next line of the source file. 70 #define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress : n)) 71 72 // Allows exporting a class that inherits from a non-exported base class. 73 // This uses suppress instead of push/pop because the delimiter after the 74 // declaration (either "," or "{") has to be placed before the pop macro. 75 // 76 // Example usage: 77 // class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) { 78 // 79 // MSVC Compiler warning C4275: 80 // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'. 81 // Note that this is intended to be used only when no access to the base class' 82 // static data is done through derived classes or inline methods. For more info, 83 // see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx 84 #define NON_EXPORTED_BASE(code) \ 85 MSVC_SUPPRESS_WARNING(4275) \ 86 code 87 88 #else // Not MSVC 89 90 #define MSVC_SUPPRESS_WARNING(n) 91 #define NON_EXPORTED_BASE(code) code 92 93 #endif // V8_CC_MSVC 94 95 // Allowing the use of noexcept by removing the keyword on older compilers that 96 // do not support adding noexcept to default members. 97 // Disabled on MSVC because constructors of standard containers are not noexcept 98 // there. 99 #if ((!defined(V8_CC_GNU) && !defined(V8_CC_MSVC) && \ 100 !defined(V8_TARGET_ARCH_MIPS) && !defined(V8_TARGET_ARCH_MIPS64) && \ 101 !defined(V8_TARGET_ARCH_PPC) && !defined(V8_TARGET_ARCH_PPC64)) || \ 102 (defined(__clang__) && __cplusplus > 201300L)) 103 #define V8_NOEXCEPT noexcept 104 #else 105 #define V8_NOEXCEPT 106 #endif 107 108 // Specify memory alignment for structs, classes, etc. 109 // Use like: 110 // class ALIGNAS(16) MyClass { ... } 111 // ALIGNAS(16) int array[4]; 112 // 113 // In most places you can use the C++11 keyword "alignas", which is preferred. 114 // 115 // But compilers have trouble mixing __attribute__((...)) syntax with 116 // alignas(...) syntax. 117 // 118 // Doesn't work in clang or gcc: 119 // struct alignas(16) __attribute__((packed)) S { char c; }; 120 // Works in clang but not gcc: 121 // struct __attribute__((packed)) alignas(16) S2 { char c; }; 122 // Works in clang and gcc: 123 // struct alignas(16) S3 { char c; } __attribute__((packed)); 124 // 125 // There are also some attributes that must be specified *before* a class 126 // definition: visibility (used for exporting functions/classes) is one of 127 // these attributes. This means that it is not possible to use alignas() with a 128 // class that is marked as exported. 129 #if defined(V8_CC_MSVC) 130 #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment)) 131 #else 132 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment))) 133 #endif 134 135 #endif // V8_BASE_COMPILER_SPECIFIC_H_ 136