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 exporting a class that inherits from a non-exported base class.
  44 // This uses suppress instead of push/pop because the delimiter after the
  45 // declaration (either "," or "{") has to be placed before the pop macro.
  46 //
  47 // Example usage:
  48 // class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) {
  49 //
  50 // MSVC Compiler warning C4275:
  51 // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
  52 // Note that this is intended to be used only when no access to the base class'
  53 // static data is done through derived classes or inline methods. For more info,
  54 // see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
  55 #define NON_EXPORTED_BASE(code) MSVC_SUPPRESS_WARNING(4275) \
  56                                 code
  57
  58 #else  // Not MSVC
  59
  60 #define MSVC_SUPPRESS_WARNING(n)
  61 #define MSVC_PUSH_DISABLE_WARNING(n)
  62 #define MSVC_PUSH_WARNING_LEVEL(n)
  63 #define MSVC_POP_WARNING()
  64 #define MSVC_DISABLE_OPTIMIZE()
  65 #define MSVC_ENABLE_OPTIMIZE()
  66 #define NON_EXPORTED_BASE(code) code
  67
  68 #endif  // COMPILER_MSVC
  69
  70
  71 // The C++ standard requires that static const members have an out-of-class
  72 // definition (in a single compilation unit), but MSVC chokes on this (when
  73 // language extensions, which are required, are enabled). (You're only likely to
  74 // notice the need for a definition if you take the address of the member or,
  75 // more commonly, pass it to a function that takes it as a reference argument --
  76 // probably an STL function.) This macro makes MSVC do the right thing. See
  77 // http://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx for more
  78 // information. Use like:
  79 //
  80 // In .h file:
  81 //   struct Foo {
  82 //     static const int kBar = 5;
  83 //   };
  84 //
  85 // In .cc file:
  86 //   STATIC_CONST_MEMBER_DEFINITION const int Foo::kBar;
  87 #if defined(COMPILER_MSVC)
  88 #define STATIC_CONST_MEMBER_DEFINITION __declspec(selectany)
  89 #else
  90 #define STATIC_CONST_MEMBER_DEFINITION
  91 #endif
  92
  93 // Annotate a variable indicating it's ok if the variable is not used.
  94 // (Typically used to silence a compiler warning when the assignment
  95 // is important for some other reason.)
  96 // Use like:
  97 //   int x ALLOW_UNUSED = ...;
  98 #if defined(COMPILER_GCC)
  99 #define ALLOW_UNUSED __attribute__((unused))
 100 #else
 101 #define ALLOW_UNUSED
 102 #endif
 103
 104 // Annotate a function indicating it should not be inlined.
 105 // Use like:
 106 //   NOINLINE void DoStuff() { ... }
 107 #if defined(COMPILER_GCC)
 108 #define NOINLINE __attribute__((noinline))
 109 #elif defined(COMPILER_MSVC)
 110 #define NOINLINE __declspec(noinline)
 111 #else
 112 #define NOINLINE
 113 #endif
 114
 115 // Specify memory alignment for structs, classes, etc.
 116 // Use like:
 117 //   class ALIGNAS(16) MyClass { ... }
 118 //   ALIGNAS(16) int array[4];
 119 #if defined(COMPILER_MSVC)
 120 #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
 121 #elif defined(COMPILER_GCC)
 122 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
 123 #endif
 124
 125 // Return the byte alignment of the given type (available at compile time).  Use
 126 // sizeof(type) prior to checking __alignof to workaround Visual C++ bug:
 127 // http://goo.gl/isH0C
 128 // Use like:
 129 //   ALIGNOF(int32)  // this would be 4
 130 #if defined(COMPILER_MSVC)
 131 #define ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
 132 #elif defined(COMPILER_GCC)
 133 #define ALIGNOF(type) __alignof__(type)
 134 #endif
 135
 136 // Annotate a virtual method indicating it must be overriding a virtual
 137 // method in the parent class.
 138 // Use like:
 139 //   virtual void foo() OVERRIDE;
 140 #if defined(__clang__) || defined(COMPILER_MSVC)
 141 #define OVERRIDE override
 142 #elif defined(COMPILER_GCC) && __cplusplus >= 201103 && \
 143       (__GNUC__ * 10000 + __GNUC_MINOR__ * 100) >= 40700
 144 // GCC 4.7 supports explicit virtual overrides when C++11 support is enabled.
 145 #define OVERRIDE override
 146 #else
 147 #define OVERRIDE
 148 #endif
 149
 150 // Annotate a virtual method indicating that subclasses must not override it,
 151 // or annotate a class to indicate that it cannot be subclassed.
 152 // Use like:
 153 //   virtual void foo() FINAL;
 154 //   class B FINAL : public A {};
 155 #if defined(__clang__) || defined(COMPILER_MSVC)
 156 #define FINAL final
 157 #elif defined(COMPILER_GCC) && __cplusplus >= 201103 && \
 158       (__GNUC__ * 10000 + __GNUC_MINOR__ * 100) >= 40700
 159 // GCC 4.7 supports explicit virtual overrides when C++11 support is enabled.
 160 #define FINAL final
 161 #else
 162 #define FINAL
 163 #endif
 164
 165 // Annotate a function indicating the caller must examine the return value.
 166 // Use like:
 167 //   int foo() WARN_UNUSED_RESULT;
 168 // To explicitly ignore a result, see |ignore_result()| in <base/basictypes.h>.
 169 #if defined(COMPILER_GCC)
 170 #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 171 #else
 172 #define WARN_UNUSED_RESULT
 173 #endif
 174
 175 // Tell the compiler a function is using a printf-style format string.
 176 // |format_param| is the one-based index of the format string parameter;
 177 // |dots_param| is the one-based index of the "..." parameter.
 178 // For v*printf functions (which take a va_list), pass 0 for dots_param.
 179 // (This is undocumented but matches what the system C headers do.)
 180 #if defined(COMPILER_GCC)
 181 #define PRINTF_FORMAT(format_param, dots_param) \
 182     __attribute__((format(printf, format_param, dots_param)))
 183 #else
 184 #define PRINTF_FORMAT(format_param, dots_param)
 185 #endif
 186
 187 // WPRINTF_FORMAT is the same, but for wide format strings.
 188 // This doesn't appear to yet be implemented in any compiler.
 189 // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
 190 #define WPRINTF_FORMAT(format_param, dots_param)
 191 // If available, it would look like:
 192 //   __attribute__((format(wprintf, format_param, dots_param)))
 193
 194 // MemorySanitizer annotations.
 195 #if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
 196 #include <sanitizer/msan_interface.h>
 197
 198 // Mark a memory region fully initialized.
 199 // Use this to annotate code that deliberately reads uninitialized data, for
 200 // example a GC scavenging root set pointers from the stack.
 201 #define MSAN_UNPOISON(p, s)  __msan_unpoison(p, s)
 202 #else  // MEMORY_SANITIZER
 203 #define MSAN_UNPOISON(p, s)
 204 #endif  // MEMORY_SANITIZER
 205
 206 // Macro useful for writing cross-platform function pointers.
 207 #if !defined(CDECL)
 208 #if defined(OS_WIN)
 209 #define CDECL __cdecl
 210 #else  // defined(OS_WIN)
 211 #define CDECL
 212 #endif  // defined(OS_WIN)
 213 #endif  // !defined(CDECL)
 214
 215 // Macro for hinting that an expression is likely to be false.
 216 #if !defined(UNLIKELY)
 217 #if defined(COMPILER_GCC)
 218 #define UNLIKELY(x) __builtin_expect(!!(x), 0)
 219 #else
 220 #define UNLIKELY(x) (x)
 221 #endif  // defined(COMPILER_GCC)
 222 #endif  // !defined(UNLIKELY)
 223
 224 #endif  // BASE_COMPILER_SPECIFIC_H_