am 601ea30c: am acf0a8b3: Merge "Revert "Add commonly used C++ macros to libbase.""

#include <string>

#include "base/macros.h"  // For TEMP_FAILURE_RETRY on Darwin.

#define LOG_TAG "base.file"

#include "cutils/log.h"

#include "utils/Compat.h"  // For TEMP_FAILURE_RETRY on Darwin.

namespace android {

namespace base {

/*

 * Copyright (C) 2015 The Android Open Source Project

 *

 * 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.

 */

#ifndef UTILS_MACROS_H

#define UTILS_MACROS_H

#include <stddef.h>  // for size_t

#include <unistd.h>  // for TEMP_FAILURE_RETRY

// bionic and glibc both have TEMP_FAILURE_RETRY, but eg Mac OS' libc doesn't.

#ifndef TEMP_FAILURE_RETRY

#define TEMP_FAILURE_RETRY(exp)            \

  ({                                       \

    decltype(exp) _rc;                     \

    do {                                   \

      _rc = (exp);                         \

    } while (_rc == -1 && errno == EINTR); \

    _rc;                                   \

  })

#endif

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

// This must be placed in the private: declarations for a class.

//

// For disallowing only assign or copy, delete the relevant operator or

// constructor, for example:

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

// 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.

//

// When building with C++11 toolchains, just use the language support

// for explicitly deleted methods.

#if __cplusplus >= 201103L

#define DISALLOW_COPY_AND_ASSIGN(TypeName) \

  TypeName(const TypeName&) = delete;      \

  void operator=(const TypeName&) = delete

#else

#define DISALLOW_COPY_AND_ASSIGN(TypeName) \

  TypeName(const TypeName&);               \

  void operator=(const TypeName&)

#endif

// 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 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];  // NOLINT(readability/casting)

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

// ARRAYSIZE_UNSAFE 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_UNSAFE(a) is a compile-time constant of type

// size_t.

//

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

//

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

//

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

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

//

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

// be ignored by the users.

//

// ARRAYSIZE_UNSAFE(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.  Since all our code has to go 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.

#define ARRAYSIZE_UNSAFE(a)     \

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

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

#define LIKELY(x) __builtin_expect((x), true)

#define UNLIKELY(x) __builtin_expect((x), false)

#define WARN_UNUSED __attribute__((warn_unused_result))

// A deprecated function to call to create a false use of the parameter, for

// example:

//   int foo(int x) { UNUSED(x); return 10; }

// to avoid compiler warnings. Going forward we prefer ATTRIBUTE_UNUSED.

template <typename... T>

void UNUSED(const T&...) {

}

// An attribute to place on a parameter to a function, for example:

//   int foo(int x ATTRIBUTE_UNUSED) { return 10; }

// to avoid compiler warnings.

#define ATTRIBUTE_UNUSED __attribute__((__unused__))

// 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 defined(__clang__) && __cplusplus >= 201103L && defined(__has_warning)

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

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

#endif

#endif

#ifndef FALLTHROUGH_INTENDED

#define FALLTHROUGH_INTENDED \

  do {                       \

  } while (0)

#endif

#endif  // UTILS_MACROS_H