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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 // 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 ALLOW_UNUSED = ...;
     76 #if defined(COMPILER_GCC)
     77 #define ALLOW_UNUSED __attribute__((unused))
     78 #else
     79 #define ALLOW_UNUSED
     80 #endif
     81 
     82 // Annotate a function indicating it should not be inlined.
     83 // Use like:
     84 //   NOINLINE void DoStuff() { ... }
     85 #if defined(COMPILER_GCC)
     86 #define NOINLINE __attribute__((noinline))
     87 #elif defined(COMPILER_MSVC)
     88 #define NOINLINE __declspec(noinline)
     89 #else
     90 #define NOINLINE
     91 #endif
     92 
     93 // Specify memory alignment for structs, classes, etc.
     94 // Use like:
     95 //   class ALIGNAS(16) MyClass { ... }
     96 //   ALIGNAS(16) int array[4];
     97 #if defined(COMPILER_MSVC)
     98 #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
     99 #elif defined(COMPILER_GCC)
    100 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
    101 #endif
    102 
    103 // Return the byte alignment of the given type (available at compile time).  Use
    104 // sizeof(type) prior to checking __alignof to workaround Visual C++ bug:
    105 // http://goo.gl/isH0C
    106 // Use like:
    107 //   ALIGNOF(int32)  // this would be 4
    108 #if defined(COMPILER_MSVC)
    109 #define ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
    110 #elif defined(COMPILER_GCC)
    111 #define ALIGNOF(type) __alignof__(type)
    112 #endif
    113 
    114 // Annotate a virtual method indicating it must be overriding a virtual
    115 // method in the parent class.
    116 // Use like:
    117 //   virtual void foo() OVERRIDE;
    118 #if defined(COMPILER_MSVC)
    119 #define OVERRIDE override
    120 #elif defined(__clang__)
    121 #define OVERRIDE override
    122 #else
    123 #define OVERRIDE
    124 #endif
    125 
    126 // Annotate a virtual method indicating that subclasses must not override it,
    127 // or annotate a class to indicate that it cannot be subclassed.
    128 // Use like:
    129 //   virtual void foo() FINAL;
    130 //   class B FINAL : public A {};
    131 #if defined(COMPILER_MSVC)
    132 // TODO(jered): Change this to "final" when chromium no longer uses MSVC 2010.
    133 #define FINAL sealed
    134 #elif defined(__clang__)
    135 #define FINAL final
    136 #else
    137 #define FINAL
    138 #endif
    139 
    140 // Annotate a function indicating the caller must examine the return value.
    141 // Use like:
    142 //   int foo() WARN_UNUSED_RESULT;
    143 // To explicitly ignore a result, see |ignore_result()| in <base/basictypes.h>.
    144 #if defined(COMPILER_GCC)
    145 #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
    146 #else
    147 #define WARN_UNUSED_RESULT
    148 #endif
    149 
    150 // Tell the compiler a function is using a printf-style format string.
    151 // |format_param| is the one-based index of the format string parameter;
    152 // |dots_param| is the one-based index of the "..." parameter.
    153 // For v*printf functions (which take a va_list), pass 0 for dots_param.
    154 // (This is undocumented but matches what the system C headers do.)
    155 #if defined(COMPILER_GCC)
    156 #define PRINTF_FORMAT(format_param, dots_param) \
    157     __attribute__((format(printf, format_param, dots_param)))
    158 #else
    159 #define PRINTF_FORMAT(format_param, dots_param)
    160 #endif
    161 
    162 // WPRINTF_FORMAT is the same, but for wide format strings.
    163 // This doesn't appear to yet be implemented in any compiler.
    164 // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
    165 #define WPRINTF_FORMAT(format_param, dots_param)
    166 // If available, it would look like:
    167 //   __attribute__((format(wprintf, format_param, dots_param)))
    168 
    169 
    170 // MemorySanitizer annotations.
    171 #ifdef MEMORY_SANITIZER
    172 extern "C" {
    173 void __msan_unpoison(const void *p, unsigned long s);
    174 }  // extern "C"
    175 
    176 // Mark a memory region fully initialized.
    177 // Use this to annotate code that deliberately reads uninitialized data, for
    178 // example a GC scavenging root set pointers from the stack.
    179 #define MSAN_UNPOISON(p, s)  __msan_unpoison(p, s)
    180 #else  // MEMORY_SANITIZER
    181 #define MSAN_UNPOISON(p, s)
    182 #endif  // MEMORY_SANITIZER
    183 
    184 #endif  // BASE_COMPILER_SPECIFIC_H_
    185