base/compiler_specific.h

   1 // Copyright (c) 2012 The Chromium 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 BASE_COMPILER_SPECIFIC_H_
   6 #define BASE_COMPILER_SPECIFIC_H_
   7
   8 #include "build/build_config.h"
   9
  10 #if defined(COMPILER_MSVC)
  11
  12 // Macros for suppressing and disabling warnings on MSVC.
  13 //
  14 // Warning numbers are enumerated at:
  15 // http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
  16 //
  17 // The warning pragma:
  18 // http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
  19 //
  20 // Using __pragma instead of #pragma inside macros:
  21 // http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
  22
  23 // MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and
  24 // for the next line of the source file.
  25 #define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress:n))
  26
  27 // MSVC_PUSH_DISABLE_WARNING pushes |n| onto a stack of warnings to be disabled.
  28 // The warning remains disabled until popped by MSVC_POP_WARNING.
  29 #define MSVC_PUSH_DISABLE_WARNING(n) __pragma(warning(push)) \
  30                                      __pragma(warning(disable:n))
  31
  32 // MSVC_PUSH_WARNING_LEVEL pushes |n| as the global warning level.  The level
  33 // remains in effect until popped by MSVC_POP_WARNING().  Use 0 to disable all
  34 // warnings.
  35 #define MSVC_PUSH_WARNING_LEVEL(n) __pragma(warning(push, n))
  36
  37 // Pop effects of innermost MSVC_PUSH_* macro.
  38 #define MSVC_POP_WARNING() __pragma(warning(pop))
  39
  40 #define MSVC_DISABLE_OPTIMIZE() __pragma(optimize("", off))
  41 #define MSVC_ENABLE_OPTIMIZE() __pragma(optimize("", on))
  42
  43 // Allows |this| to be passed as an argument in constructor initializer lists.
  44 // This uses push/pop instead of the seemingly simpler suppress feature to avoid
  45 // having the warning be disabled for more than just |code|.
  46 //
  47 // Example usage:
  48 // Foo::Foo() : x(NULL), ALLOW_THIS_IN_INITIALIZER_LIST(y(this)), z(3) {}
  49 //
  50 // Compiler warning C4355: 'this': used in base member initializer list:
  51 // http://msdn.microsoft.com/en-us/library/3c594ae3(VS.80).aspx
  52 #define ALLOW_THIS_IN_INITIALIZER_LIST(code) MSVC_PUSH_DISABLE_WARNING(4355) \
  53                                              code \
  54                                              MSVC_POP_WARNING()
  55
  56 // Allows exporting a class that inherits from a non-exported base class.
  57 // This uses suppress instead of push/pop because the delimiter after the
  58 // declaration (either "," or "{") has to be placed before the pop macro.
  59 //
  60 // Example usage:
  61 // class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) {
  62 //
  63 // MSVC Compiler warning C4275:
  64 // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
  65 // Note that this is intended to be used only when no access to the base class'
  66 // static data is done through derived classes or inline methods. For more info,
  67 // see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
  68 #define NON_EXPORTED_BASE(code) MSVC_SUPPRESS_WARNING(4275) \
  69                                 code
  70
  71 #else  // Not MSVC
  72
  73 #define MSVC_SUPPRESS_WARNING(n)
  74 #define MSVC_PUSH_DISABLE_WARNING(n)
  75 #define MSVC_PUSH_WARNING_LEVEL(n)
  76 #define MSVC_POP_WARNING()
  77 #define MSVC_DISABLE_OPTIMIZE()
  78 #define MSVC_ENABLE_OPTIMIZE()
  79 #define ALLOW_THIS_IN_INITIALIZER_LIST(code) code
  80 #define NON_EXPORTED_BASE(code) code
  81
  82 #endif  // COMPILER_MSVC
  83
  84
  85 // Annotate a variable indicating it's ok if the variable is not used.
  86 // (Typically used to silence a compiler warning when the assignment
  87 // is important for some other reason.)
  88 // Use like:
  89 //   int x ALLOW_UNUSED = ...;
  90 #if defined(COMPILER_GCC)
  91 #define ALLOW_UNUSED __attribute__((unused))
  92 #else
  93 #define ALLOW_UNUSED
  94 #endif
  95
  96 // Annotate a function indicating it should not be inlined.
  97 // Use like:
  98 //   NOINLINE void DoStuff() { ... }
  99 #if defined(COMPILER_GCC)
 100 #define NOINLINE __attribute__((noinline))
 101 #elif defined(COMPILER_MSVC)
 102 #define NOINLINE __declspec(noinline)
 103 #else
 104 #define NOINLINE
 105 #endif
 106
 107 // Specify memory alignment for structs, classes, etc.
 108 // Use like:
 109 //   class ALIGNAS(16) MyClass { ... }
 110 //   ALIGNAS(16) int array[4];
 111 #if defined(COMPILER_MSVC)
 112 #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
 113 #elif defined(COMPILER_GCC)
 114 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
 115 #endif
 116
 117 // Return the byte alignment of the given type (available at compile time).  Use
 118 // sizeof(type) prior to checking __alignof to workaround Visual C++ bug:
 119 // http://goo.gl/isH0C
 120 // Use like:
 121 //   ALIGNOF(int32)  // this would be 4
 122 #if defined(COMPILER_MSVC)
 123 #define ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
 124 #elif defined(COMPILER_GCC)
 125 #define ALIGNOF(type) __alignof__(type)
 126 #endif
 127
 128 // Annotate a virtual method indicating it must be overriding a virtual
 129 // method in the parent class.
 130 // Use like:
 131 //   virtual void foo() OVERRIDE;
 132 #if defined(COMPILER_MSVC)
 133 #define OVERRIDE override
 134 #elif defined(__clang__)
 135 #define OVERRIDE override
 136 #else
 137 #define OVERRIDE
 138 #endif
 139
 140 // Annotate a function indicating the caller must examine the return value.
 141 // Use like:
 142 //   int foo() WARN_UNUSED_RESULT;
 143 // To explicitly ignore a result, see |ignore_result()| in <base/basictypes.h>.
 144 #if defined(COMPILER_GCC)
 145 #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 146 #else
 147 #define WARN_UNUSED_RESULT
 148 #endif
 149
 150 // Tell the compiler a function is using a printf-style format string.
 151 // |format_param| is the one-based index of the format string parameter;
 152 // |dots_param| is the one-based index of the "..." parameter.
 153 // For v*printf functions (which take a va_list), pass 0 for dots_param.
 154 // (This is undocumented but matches what the system C headers do.)
 155 #if defined(COMPILER_GCC)
 156 #define PRINTF_FORMAT(format_param, dots_param) \
 157     __attribute__((format(printf, format_param, dots_param)))
 158 #else
 159 #define PRINTF_FORMAT(format_param, dots_param)
 160 #endif
 161
 162 // WPRINTF_FORMAT is the same, but for wide format strings.
 163 // This doesn't appear to yet be implemented in any compiler.
 164 // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
 165 #define WPRINTF_FORMAT(format_param, dots_param)
 166 // If available, it would look like:
 167 //   __attribute__((format(wprintf, format_param, dots_param)))
 168
 169 #endif  // BASE_COMPILER_SPECIFIC_H_