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/*
* 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 ANDROID_BASE_MACROS_H
#define ANDROID_BASE_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.
//
// When building with C++11 toolchains, just use the language support
// for explicitly deleted methods.
#if __cplusplus >= 201103L
#define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
TypeName() = delete; \
DISALLOW_COPY_AND_ASSIGN(TypeName)
#else
#define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
TypeName(); \
DISALLOW_COPY_AND_ASSIGN(TypeName)
#endif
// 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)))))
// Changing this definition will cause you a lot of pain. A majority of
// vendor code defines LIKELY and UNLIKELY this way, and includes
// this header through an indirect path.
#define LIKELY( exp ) (__builtin_expect( (exp) != 0, true ))
#define UNLIKELY( exp ) (__builtin_expect( (exp) != 0, 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 // ANDROID_BASE_MACROS_H
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