text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef BASE_COMPILER_SPECIFIC_H_
  #define BASE_COMPILER_SPECIFIC_H_
  
  #include "build/build_config.h"
  
  #if defined(COMPILER_MSVC)
  
  // Macros for suppressing and disabling warnings on MSVC.
  //
  // Warning numbers are enumerated at:
  // http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
  //
  // The warning pragma:
  // http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
  //
  // Using __pragma instead of #pragma inside macros:
  // http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
  
  // MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and
  // for the next line of the source file.
  #define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress:n))
  
  // MSVC_PUSH_DISABLE_WARNING pushes |n| onto a stack of warnings to be disabled.
  // The warning remains disabled until popped by MSVC_POP_WARNING.
  #define MSVC_PUSH_DISABLE_WARNING(n) __pragma(warning(push)) \
                                       __pragma(warning(disable:n))
  
  // MSVC_PUSH_WARNING_LEVEL pushes |n| as the global warning level.  The level
  // remains in effect until popped by MSVC_POP_WARNING().  Use 0 to disable all
  // warnings.
  #define MSVC_PUSH_WARNING_LEVEL(n) __pragma(warning(push, n))
  
  // Pop effects of innermost MSVC_PUSH_* macro.
  #define MSVC_POP_WARNING() __pragma(warning(pop))
  
  #define MSVC_DISABLE_OPTIMIZE() __pragma(optimize("", off))
  #define MSVC_ENABLE_OPTIMIZE() __pragma(optimize("", on))
  
  // Allows exporting a class that inherits from a non-exported base class.
  // This uses suppress instead of push/pop because the delimiter after the
  // declaration (either "," or "{") has to be placed before the pop macro.
  //
  // Example usage:
  // class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) {
  //
  // MSVC Compiler warning C4275:
  // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
  // Note that this is intended to be used only when no access to the base class'
  // static data is done through derived classes or inline methods. For more info,
  // see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
  #define NON_EXPORTED_BASE(code) MSVC_SUPPRESS_WARNING(4275) \
                                  code
  
  #else  // Not MSVC
  
  #define MSVC_SUPPRESS_WARNING(n)
  #define MSVC_PUSH_DISABLE_WARNING(n)
  #define MSVC_PUSH_WARNING_LEVEL(n)
  #define MSVC_POP_WARNING()
  #define MSVC_DISABLE_OPTIMIZE()
  #define MSVC_ENABLE_OPTIMIZE()
  #define NON_EXPORTED_BASE(code) code
  
  #endif  // COMPILER_MSVC
  
  
  // The C++ standard requires that static const members have an out-of-class
  // definition (in a single compilation unit), but MSVC chokes on this (when
  // language extensions, which are required, are enabled). (You're only likely to
  // notice the need for a definition if you take the address of the member or,
  // more commonly, pass it to a function that takes it as a reference argument --
  // probably an STL function.) This macro makes MSVC do the right thing. See
  // http://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx for more
  // information. Use like:
  //
  // In .h file:
  //   struct Foo {
  //     static const int kBar = 5;
  //   };
  //
  // In .cc file:
  //   STATIC_CONST_MEMBER_DEFINITION const int Foo::kBar;
  #if defined(COMPILER_MSVC)
  #define STATIC_CONST_MEMBER_DEFINITION __declspec(selectany)
  #else
  #define STATIC_CONST_MEMBER_DEFINITION
  #endif
  
  // Annotate a variable indicating it's ok if the variable is not used.
  // (Typically used to silence a compiler warning when the assignment
  // is important for some other reason.)
  // Use like:
  //   int x = ...;
  //   ALLOW_UNUSED_LOCAL(x);
  #define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0
  
  // Annotate a typedef or function indicating it's ok if it's not used.
  // Use like:
  //   typedef Foo Bar ALLOW_UNUSED_TYPE;
  #if defined(COMPILER_GCC)
  #define ALLOW_UNUSED_TYPE __attribute__((unused))
  #else
  #define ALLOW_UNUSED_TYPE
  #endif
  
  // Annotate a function indicating it should not be inlined.
  // Use like:
  //   NOINLINE void DoStuff() { ... }
  #if defined(COMPILER_GCC)
  #define NOINLINE __attribute__((noinline))
  #elif defined(COMPILER_MSVC)
  #define NOINLINE __declspec(noinline)
  #else
  #define NOINLINE
  #endif
  
  // Specify memory alignment for structs, classes, etc.
  // Use like:
  //   class ALIGNAS(16) MyClass { ... }
  //   ALIGNAS(16) int array[4];
  #if defined(COMPILER_MSVC)
  #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
  #elif defined(COMPILER_GCC)
  #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
  #endif
  
  // Return the byte alignment of the given type (available at compile time).
  // Use like:
  //   ALIGNOF(int32)  // this would be 4
  #if defined(COMPILER_MSVC)
  #define ALIGNOF(type) __alignof(type)
  #elif defined(COMPILER_GCC)
  #define ALIGNOF(type) __alignof__(type)
  #endif
  
  // Annotate a function indicating the caller must examine the return value.
  // Use like:
  //   int foo() WARN_UNUSED_RESULT;
  // To explicitly ignore a result, see |ignore_result()| in base/macros.h.
  #if defined(COMPILER_GCC)
  #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
  #else
  #define WARN_UNUSED_RESULT
  #endif
  
  // Tell the compiler a function is using a printf-style format string.
  // |format_param| is the one-based index of the format string parameter;
  // |dots_param| is the one-based index of the "..." parameter.
  // For v*printf functions (which take a va_list), pass 0 for dots_param.
  // (This is undocumented but matches what the system C headers do.)
  #if defined(COMPILER_GCC)
  #define PRINTF_FORMAT(format_param, dots_param) \
      __attribute__((format(printf, format_param, dots_param)))
  #else
  #define PRINTF_FORMAT(format_param, dots_param)
  #endif
  
  // WPRINTF_FORMAT is the same, but for wide format strings.
  // This doesn't appear to yet be implemented in any compiler.
  // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
  #define WPRINTF_FORMAT(format_param, dots_param)
  // If available, it would look like:
  //   __attribute__((format(wprintf, format_param, dots_param)))
  
  // MemorySanitizer annotations.
  #if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
  #include <sanitizer/msan_interface.h>
  
  // Mark a memory region fully initialized.
  // Use this to annotate code that deliberately reads uninitialized data, for
  // example a GC scavenging root set pointers from the stack.
  #define MSAN_UNPOISON(p, size)  __msan_unpoison(p, size)
  
  // Check a memory region for initializedness, as if it was being used here.
  // If any bits are uninitialized, crash with an MSan report.
  // Use this to sanitize data which MSan won't be able to track, e.g. before
  // passing data to another process via shared memory.
  #define MSAN_CHECK_MEM_IS_INITIALIZED(p, size) \
      __msan_check_mem_is_initialized(p, size)
  #else  // MEMORY_SANITIZER
  #define MSAN_UNPOISON(p, size)
  #define MSAN_CHECK_MEM_IS_INITIALIZED(p, size)
  #endif  // MEMORY_SANITIZER
  
  // Macro useful for writing cross-platform function pointers.
  #if !defined(CDECL)
  #if defined(OS_WIN)
  #define CDECL __cdecl
  #else  // defined(OS_WIN)
  #define CDECL
  #endif  // defined(OS_WIN)
  #endif  // !defined(CDECL)
  
  // Macro for hinting that an expression is likely to be false.
  #if !defined(UNLIKELY)
  #if defined(COMPILER_GCC)
  #define UNLIKELY(x) __builtin_expect(!!(x), 0)
  #else
  #define UNLIKELY(x) (x)
  #endif  // defined(COMPILER_GCC)
  #endif  // !defined(UNLIKELY)
  
  #endif  // BASE_COMPILER_SPECIFIC_H_
  