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 = ...;
  98 //   ALLOW_UNUSED_LOCAL(x);
  99 #define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0
 100
 101 // Annotate a typedef or function indicating it's ok if it's not used.
 102 // Use like:
 103 //   typedef Foo Bar ALLOW_UNUSED_TYPE;
 104 #if defined(COMPILER_GCC)
 105 #define ALLOW_UNUSED_TYPE __attribute__((unused))
 106 #else
 107 #define ALLOW_UNUSED_TYPE
 108 #endif
 109
 110 // Annotate a function indicating it should not be inlined.
 111 // Use like:
 112 //   NOINLINE void DoStuff() { ... }
 113 #if defined(COMPILER_GCC)
 114 #define NOINLINE __attribute__((noinline))
 115 #elif defined(COMPILER_MSVC)
 116 #define NOINLINE __declspec(noinline)
 117 #else
 118 #define NOINLINE
 119 #endif
 120
 121 // Specify memory alignment for structs, classes, etc.
 122 // Use like:
 123 //   class ALIGNAS(16) MyClass { ... }
 124 //   ALIGNAS(16) int array[4];
 125 #if defined(COMPILER_MSVC)
 126 #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
 127 #elif defined(COMPILER_GCC)
 128 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
 129 #endif
 130
 131 // Return the byte alignment of the given type (available at compile time).  Use
 132 // sizeof(type) prior to checking __alignof to workaround Visual C++ bug:
 133 // http://goo.gl/isH0C
 134 // Use like:
 135 //   ALIGNOF(int32)  // this would be 4
 136 #if defined(COMPILER_MSVC)
 137 #define ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
 138 #elif defined(COMPILER_GCC)
 139 #define ALIGNOF(type) __alignof__(type)
 140 #endif
 141
 142 // Annotate a function indicating the caller must examine the return value.
 143 // Use like:
 144 //   int foo() WARN_UNUSED_RESULT;
 145 // To explicitly ignore a result, see |ignore_result()| in <base/basictypes.h>.
 146 #if defined(COMPILER_GCC)
 147 #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 148 #else
 149 #define WARN_UNUSED_RESULT
 150 #endif
 151
 152 // Tell the compiler a function is using a printf-style format string.
 153 // |format_param| is the one-based index of the format string parameter;
 154 // |dots_param| is the one-based index of the "..." parameter.
 155 // For v*printf functions (which take a va_list), pass 0 for dots_param.
 156 // (This is undocumented but matches what the system C headers do.)
 157 #if defined(COMPILER_GCC)
 158 #define PRINTF_FORMAT(format_param, dots_param) \
 159     __attribute__((format(printf, format_param, dots_param)))
 160 #else
 161 #define PRINTF_FORMAT(format_param, dots_param)
 162 #endif
 163
 164 // WPRINTF_FORMAT is the same, but for wide format strings.
 165 // This doesn't appear to yet be implemented in any compiler.
 166 // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
 167 #define WPRINTF_FORMAT(format_param, dots_param)
 168 // If available, it would look like:
 169 //   __attribute__((format(wprintf, format_param, dots_param)))
 170
 171 // MemorySanitizer annotations.
 172 #if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
 173 #include <sanitizer/msan_interface.h>
 174
 175 // Mark a memory region fully initialized.
 176 // Use this to annotate code that deliberately reads uninitialized data, for
 177 // example a GC scavenging root set pointers from the stack.
 178 #define MSAN_UNPOISON(p, s)  __msan_unpoison(p, s)
 179 #else  // MEMORY_SANITIZER
 180 #define MSAN_UNPOISON(p, s)
 181 #endif  // MEMORY_SANITIZER
 182
 183 // Macro useful for writing cross-platform function pointers.
 184 #if !defined(CDECL)
 185 #if defined(OS_WIN)
 186 #define CDECL __cdecl
 187 #else  // defined(OS_WIN)
 188 #define CDECL
 189 #endif  // defined(OS_WIN)
 190 #endif  // !defined(CDECL)
 191
 192 // Macro for hinting that an expression is likely to be false.
 193 #if !defined(UNLIKELY)
 194 #if defined(COMPILER_GCC)
 195 #define UNLIKELY(x) __builtin_expect(!!(x), 0)
 196 #else
 197 #define UNLIKELY(x) (x)
 198 #endif  // defined(COMPILER_GCC)
 199 #endif  // !defined(UNLIKELY)
 200
 201 #endif  // BASE_COMPILER_SPECIFIC_H_