cef/include/base/cef_macros.h

// Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2012
// Google Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef CEF_INCLUDE_BASE_CEF_MACROS_H_
#define CEF_INCLUDE_BASE_CEF_MACROS_H_
#pragma once

#if defined(USING_CHROMIUM_INCLUDES)
// When building CEF include the Chromium header directly.
#include "base/macros.h"

#else  // !USING_CHROMIUM_INCLUDES
// The following is substantially similar to the Chromium implementation.
// If the Chromium implementation diverges the below implementation should be
// updated to match.

#include <stddef.h>  // For size_t.
#include "include/base/cef_build.h"  // For COMPILER_MSVC

#if !defined(arraysize)

// The arraysize(arr) macro returns the # of elements in an array arr.
// The expression is a compile-time constant, and therefore can be
// used in defining new arrays, for example.  If you use arraysize on
// a pointer by mistake, you will get a compile-time error.
//
// One caveat is that arraysize() doesn't accept any array of an
// anonymous type or a type defined inside a function.  In these rare
// cases, you have to use the unsafe ARRAYSIZE_UNSAFE() macro below.  This is
// due to a limitation in C++'s template system.  The limitation might
// eventually be removed, but it hasn't happened yet.

// This template function declaration is used in defining arraysize.
// Note that the function doesn't need an implementation, as we only
// use its type.
template <typename T, size_t N>
char (&ArraySizeHelper(T (&array)[N]))[N];

// That gcc wants both of these prototypes seems mysterious. VC, for
// its part, can't decide which to use (another mystery). Matching of
// template overloads: the final frontier.
#ifndef _MSC_VER
template <typename T, size_t N>
char (&ArraySizeHelper(const T (&array)[N]))[N];
#endif

#define arraysize(array) (sizeof(ArraySizeHelper(array)))

#endif  // !arraysize

#if !defined(DISALLOW_COPY_AND_ASSIGN)

// A macro to disallow the copy constructor and operator= functions
// This should be used in the private: declarations for a class
#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
  TypeName(const TypeName&);               \
  void operator=(const TypeName&)

#endif  // !DISALLOW_COPY_AND_ASSIGN

#if !defined(DISALLOW_IMPLICIT_CONSTRUCTORS)

// A macro to disallow all the implicit constructors, namely the
// default constructor, copy constructor and operator= functions.
//
// This should be used in the private: declarations for a class
// that wants to prevent anyone from instantiating it. This is
// especially useful for classes containing only static methods.
#define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
  TypeName();                                    \
  DISALLOW_COPY_AND_ASSIGN(TypeName)

#endif  // !DISALLOW_IMPLICIT_CONSTRUCTORS

#if !defined(COMPILE_ASSERT)

// The COMPILE_ASSERT macro can be used to verify that a compile time
// expression is true. For example, you could use it to verify the
// size of a static array:
//
//   COMPILE_ASSERT(ARRAYSIZE_UNSAFE(content_type_names) == CONTENT_NUM_TYPES,
//                  content_type_names_incorrect_size);
//
// or to make sure a struct is smaller than a certain size:
//
//   COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large);
//
// The second argument to the macro is the name of the variable. If
// the expression is false, most compilers will issue a warning/error
// containing the name of the variable.

#if __cplusplus >= 201103L

// Under C++11, just use static_assert.
#define COMPILE_ASSERT(expr, msg) static_assert(expr, #msg)

#else

namespace cef {

template <bool>
struct CompileAssert {
};

}  // namespace cef

#define COMPILE_ASSERT(expr, msg) \
  typedef cef::CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] \
      ALLOW_UNUSED_TYPE

// Implementation details of COMPILE_ASSERT:
//
// - COMPILE_ASSERT works by defining an array type that has -1
//   elements (and thus is invalid) when the expression is false.
//
// - The simpler definition
//
//     #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1]
//
//   does not work, as gcc supports variable-length arrays whose sizes
//   are determined at run-time (this is gcc's extension and not part
//   of the C++ standard).  As a result, gcc fails to reject the
//   following code with the simple definition:
//
//     int foo;
//     COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is
//                               // not a compile-time constant.
//
// - By using the type CompileAssert<(bool(expr))>, we ensures that
//   expr is a compile-time constant.  (Template arguments must be
//   determined at compile-time.)
//
// - The outer parentheses in CompileAssert<(bool(expr))> are necessary
//   to work around a bug in gcc 3.4.4 and 4.0.1.  If we had written
//
//     CompileAssert<bool(expr)>
//
//   instead, these compilers will refuse to compile
//
//     COMPILE_ASSERT(5 > 0, some_message);
//
//   (They seem to think the ">" in "5 > 0" marks the end of the
//   template argument list.)
//
// - The array size is (bool(expr) ? 1 : -1), instead of simply
//
//     ((expr) ? 1 : -1).
//
//   This is to avoid running into a bug in MS VC 7.1, which
//   causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1.

#endif  // !(__cplusplus >= 201103L)

#endif  // !defined(COMPILE_ASSERT)

#endif  // !USING_CHROMIUM_INCLUDES

#if !defined(ALLOW_THIS_IN_INITIALIZER_LIST)
#if defined(COMPILER_MSVC)

// 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))

// Allows |this| to be passed as an argument in constructor initializer lists.
// This uses push/pop instead of the seemingly simpler suppress feature to avoid
// having the warning be disabled for more than just |code|.
//
// Example usage:
// Foo::Foo() : x(NULL), ALLOW_THIS_IN_INITIALIZER_LIST(y(this)), z(3) {}
//
// Compiler warning C4355: 'this': used in base member initializer list:
// http://msdn.microsoft.com/en-us/library/3c594ae3(VS.80).aspx
#define ALLOW_THIS_IN_INITIALIZER_LIST(code) MSVC_PUSH_DISABLE_WARNING(4355) \
                                             code \
                                             MSVC_POP_WARNING()
#else  // !COMPILER_MSVC

#define ALLOW_THIS_IN_INITIALIZER_LIST(code) code

#endif  // !COMPILER_MSVC
#endif  // !ALLOW_THIS_IN_INITIALIZER_LIST

#endif  // CEF_INCLUDE_BASE_CEF_MACROS_H_