YugabyteDB (2.13.1.0-b60, 21121d69985fbf76aa6958d8f04a9bfa936293b5)

// Copyright 2008 Google Inc. All Rights Reserved.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

// in compliance with the License.  You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software distributed under the License

// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

// or implied.  See the License for the specific language governing permissions and limitations

// under the License.

//

// Various Google-specific macros.

//

// This code is compiled directly on many platforms, including client

// platforms like Windows, Mac, and embedded systems.  Before making

// any changes here, make sure that you're not breaking any platforms.

//

#ifndef YB_GUTIL_MACROS_H

#define YB_GUTIL_MACROS_H

#include <stddef.h>         // For size_t

#include "yb/gutil/port.h"

// The swigged version of an abstract class must be concrete if any methods

// return objects of the abstract type. We keep it abstract in C++ and

// concrete for swig.

#ifndef SWIG

#define ABSTRACT = 0

#endif

// 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(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.

template <bool>

struct CompileAssert {

};

#define COMPILE_ASSERT(expr, msg) \

  typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] ATTRIBUTE_UNUSED

// 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.

// A macro to disallow the copy constructor and operator= functions

// This should be used in the private: declarations for a class

//

// For disallowing only assign or copy, write the code directly, but declare

// the intend in a comment, for example:

// void operator=(const TypeName&);  // DISALLOW_ASSIGN

// Note, that most uses of DISALLOW_ASSIGN and DISALLOW_COPY are broken

// semantically, one should either use disallow both or neither. Try to

// avoid these in new code.

//

// The LANG_CXX11 branch is a workaround for

// http://gcc.gnu.org/PR51213 in gcc-4.7 / Crosstool v16.

// TODO(user): Remove "&& !defined(__clang_)" when =delete is

// gcc-4.7 before =delete is allowed, go back to the C++98 definition.

#if LANG_CXX11 && !defined(__clang__)

#ifndef DISALLOW_COPY_AND_ASSIGN

#define DISALLOW_COPY_AND_ASSIGN(TypeName) \

  TypeName(const TypeName&) = delete;      \

  void operator=(const TypeName&) = delete

#endif

#else

#ifndef DISALLOW_COPY_AND_ASSIGN

#define DISALLOW_COPY_AND_ASSIGN(TypeName) \

  TypeName(const TypeName&);               \

  void operator=(const TypeName&)

#endif

#endif

// An older, politically incorrect name for the above.

// Prefer DISALLOW_COPY_AND_ASSIGN for new code.

#define DISALLOW_EVIL_CONSTRUCTORS(TypeName) DISALLOW_COPY_AND_ASSIGN(TypeName)

// 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)

// 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, for C++03, 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() macro below.  This is

// due to a limitation in C++03's template system.  The limitation has

// been removed in C++11.

// 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)))

// ARRAYSIZE performs essentially the same calculation as arraysize,

// but can be used on anonymous types or types defined inside

// functions.  It's less safe than arraysize as it accepts some

// (although not all) pointers.  Therefore, you should use arraysize

// whenever possible.

//

// The expression ARRAYSIZE(a) is a compile-time constant of type

// size_t.

//

// ARRAYSIZE catches a few type errors.  If you see a compiler error

//

//   "warning: division by zero in ..."

//

// when using ARRAYSIZE, you are (wrongfully) giving it a pointer.

// You should only use ARRAYSIZE on statically allocated arrays.

//

// The following comments are on the implementation details, and can

// be ignored by the users.

//

// ARRAYSIZE(arr) works by inspecting sizeof(arr) (the # of bytes in

// the array) and sizeof(*(arr)) (the # of bytes in one array

// element).  If the former is divisible by the latter, perhaps arr is

// indeed an array, in which case the division result is the # of

// elements in the array.  Otherwise, arr cannot possibly be an array,

// and we generate a compiler error to prevent the code from

// compiling.

//

// Since the size of bool is implementation-defined, we need to cast

// !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final

// result has type size_t.

//

// This macro is not perfect as it wrongfully accepts certain

// pointers, namely where the pointer size is divisible by the pointee

// size.  For code that goes through a 32-bit compiler, where a pointer

// is 4 bytes, this means all pointers to a type whose size is 3 or

// greater than 4 will be (righteously) rejected.

//

// Kudos to Jorg Brown for this simple and elegant implementation.

//

// - wan 2005-11-16

//

// Starting with Visual C++ 2005, WinNT.h includes ARRAYSIZE.

#if !defined(_MSC_VER) || (defined(_MSC_VER) && _MSC_VER < 1400)

#define ARRAYSIZE(a) \

  ((sizeof(a) / sizeof(*(a))) / \

   static_cast<size_t>(!(sizeof(a) % sizeof(*(a)))))

#endif

// A macro to turn a symbol into a string

#define AS_STRING(x)   AS_STRING_INTERNAL(x)

#define AS_STRING_INTERNAL(x)   #x

// Macro that allows definition of a variable appended with the current line

// number in the source file. Typically for use by other macros to allow the

// user to declare multiple variables with the same "base" name inside the same

// lexical block.

#define VARNAME_LINENUM(varname) VARNAME_LINENUM_INTERNAL(varname ## _L, __LINE__)

#define VARNAME_LINENUM_INTERNAL(v, line) VARNAME_LINENUM_INTERNAL2(v, line)

#define VARNAME_LINENUM_INTERNAL2(v, line) v ## line

// The following enum should be used only as a constructor argument to indicate

// that the variable has static storage class, and that the constructor should

// do nothing to its state.  It indicates to the reader that it is legal to

// declare a static instance of the class, provided the constructor is given

// the base::LINKER_INITIALIZED argument.  Normally, it is unsafe to declare a

// static variable that has a constructor or a destructor because invocation

// order is undefined.  However, IF the type can be initialized by filling with

// zeroes (which the loader does for static variables), AND the type's

// destructor does nothing to the storage, then a constructor for static

// initialization can be declared as

//       explicit MyClass(base::LinkerInitialized x) {}

// and invoked as

//       static MyClass my_variable_name(base::LINKER_INITIALIZED);

namespace base {

enum LinkerInitialized { LINKER_INITIALIZED };

}

// The FALLTHROUGH_INTENDED macro can be used to annotate implicit fall-through

// between switch labels:

//  switch (x) {

//    case 40:

//    case 41:

//      if (truth_is_out_there) {

//        ++x;

//        FALLTHROUGH_INTENDED;  // Use instead of/along with annotations in

//                               // comments.

//      } else {

//        return x;

//      }

//    case 42:

//      ...

//

//  As shown in the example above, the FALLTHROUGH_INTENDED macro should be

//  followed by a semicolon. It is designed to mimic control-flow statements

//  like 'break;', so it can be placed in most places where 'break;' can, but

//  only if there are no statements on the execution path between it and the

//  next switch label.

//

//  When compiled with clang in C++11 mode, the FALLTHROUGH_INTENDED macro is

//  expanded to [[clang::fallthrough]] attribute, which is analysed when

//  performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough').

//  See clang documentation on language extensions for details:

//  http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough

//

//  When used with unsupported compilers, the FALLTHROUGH_INTENDED macro has no

//  effect on diagnostics.

//

//  In either case this macro has no effect on runtime behavior and performance

//  of code.

#if __cplusplus >= 201703L

#define FALLTHROUGH_INTENDED [[fallthrough]]

#elif defined(__clang__) && defined(LANG_CXX11) && defined(__has_warning)

#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")

#define FALLTHROUGH_INTENDED [[clang::fallthrough]]  // NOLINT

#endif

#elif defined(__GNUC__) && __GNUC__ >= 7

#define FALLTHROUGH_INTENDED [[gnu::fallthrough]]

#endif

#ifndef FALLTHROUGH_INTENDED

#define FALLTHROUGH_INTENDED do { } while (0)

#endif

// Generally it is better to not initialize variables with default values to let the compiler find

// branches where we don't set it and then use instead of masking issues and silently use dummy

// values incorrectly.

// But for FASTDEBUG build GCC 5.5 can't handle this correctly and issues false alarm, so

// we use default initialization specifically for this case.

#ifdef FASTDEBUG

#define FASTDEBUG_FAKE_INIT(x) {x}

#else

#define FASTDEBUG_FAKE_INIT(x)

#endif

#endif  // YB_GUTIL_MACROS_H