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