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      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_
    225