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 // Annotate a variable indicating it's ok if the variable is not used.
  72 // (Typically used to silence a compiler warning when the assignment
  73 // is important for some other reason.)
  74 // Use like:
  75 //   int x = ...;
  76 //   ALLOW_UNUSED_LOCAL(x);
  77 #define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0
  78
  79 // Annotate a typedef or function indicating it's ok if it's not used.
  80 // Use like:
  81 //   typedef Foo Bar ALLOW_UNUSED_TYPE;
  82 #if defined(COMPILER_GCC) || defined(__clang__)
  83 #define ALLOW_UNUSED_TYPE __attribute__((unused))
  84 #else
  85 #define ALLOW_UNUSED_TYPE
  86 #endif
  87
  88 // Annotate a function indicating it should not be inlined.
  89 // Use like:
  90 //   NOINLINE void DoStuff() { ... }
  91 #if defined(COMPILER_GCC)
  92 #define NOINLINE __attribute__((noinline))
  93 #elif defined(COMPILER_MSVC)
  94 #define NOINLINE __declspec(noinline)
  95 #else
  96 #define NOINLINE
  97 #endif
  98
  99 // Specify memory alignment for structs, classes, etc.
 100 // Use like:
 101 //   class ALIGNAS(16) MyClass { ... }
 102 //   ALIGNAS(16) int array[4];
 103 #if defined(COMPILER_MSVC)
 104 #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
 105 #elif defined(COMPILER_GCC)
 106 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
 107 #endif
 108
 109 // Return the byte alignment of the given type (available at compile time).
 110 // Use like:
 111 //   ALIGNOF(int32)  // this would be 4
 112 #if defined(COMPILER_MSVC)
 113 #define ALIGNOF(type) __alignof(type)
 114 #elif defined(COMPILER_GCC)
 115 #define ALIGNOF(type) __alignof__(type)
 116 #endif
 117
 118 // Annotate a function indicating the caller must examine the return value.
 119 // Use like:
 120 //   int foo() WARN_UNUSED_RESULT;
 121 // To explicitly ignore a result, see |ignore_result()| in base/macros.h.
 122 #if defined(COMPILER_GCC)
 123 #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 124 #else
 125 #define WARN_UNUSED_RESULT
 126 #endif
 127
 128 // Tell the compiler a function is using a printf-style format string.
 129 // |format_param| is the one-based index of the format string parameter;
 130 // |dots_param| is the one-based index of the "..." parameter.
 131 // For v*printf functions (which take a va_list), pass 0 for dots_param.
 132 // (This is undocumented but matches what the system C headers do.)
 133 #if defined(COMPILER_GCC)
 134 #define PRINTF_FORMAT(format_param, dots_param) \
 135     __attribute__((format(printf, format_param, dots_param)))
 136 #else
 137 #define PRINTF_FORMAT(format_param, dots_param)
 138 #endif
 139
 140 // WPRINTF_FORMAT is the same, but for wide format strings.
 141 // This doesn't appear to yet be implemented in any compiler.
 142 // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
 143 #define WPRINTF_FORMAT(format_param, dots_param)
 144 // If available, it would look like:
 145 //   __attribute__((format(wprintf, format_param, dots_param)))
 146
 147 // MemorySanitizer annotations.
 148 #if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
 149 #include <sanitizer/msan_interface.h>
 150
 151 // Mark a memory region fully initialized.
 152 // Use this to annotate code that deliberately reads uninitialized data, for
 153 // example a GC scavenging root set pointers from the stack.
 154 #define MSAN_UNPOISON(p, size)  __msan_unpoison(p, size)
 155
 156 // Check a memory region for initializedness, as if it was being used here.
 157 // If any bits are uninitialized, crash with an MSan report.
 158 // Use this to sanitize data which MSan won't be able to track, e.g. before
 159 // passing data to another process via shared memory.
 160 #define MSAN_CHECK_MEM_IS_INITIALIZED(p, size) \
 161     __msan_check_mem_is_initialized(p, size)
 162 #else  // MEMORY_SANITIZER
 163 #define MSAN_UNPOISON(p, size)
 164 #define MSAN_CHECK_MEM_IS_INITIALIZED(p, size)
 165 #endif  // MEMORY_SANITIZER
 166
 167 // Macro useful for writing cross-platform function pointers.
 168 #if !defined(CDECL)
 169 #if defined(OS_WIN)
 170 #define CDECL __cdecl
 171 #else  // defined(OS_WIN)
 172 #define CDECL
 173 #endif  // defined(OS_WIN)
 174 #endif  // !defined(CDECL)
 175
 176 // Macro for hinting that an expression is likely to be false.
 177 #if !defined(UNLIKELY)
 178 #if defined(COMPILER_GCC)
 179 #define UNLIKELY(x) __builtin_expect(!!(x), 0)
 180 #else
 181 #define UNLIKELY(x) (x)
 182 #endif  // defined(COMPILER_GCC)
 183 #endif  // !defined(UNLIKELY)
 184
 185 #endif  // BASE_COMPILER_SPECIFIC_H_