base/include/android-base/macros.h - android-core - Git at Google


            
            /*

            
             * 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.

            
            #define DISALLOW_COPY_AND_ASSIGN(TypeName) \

            
              TypeName(const TypeName&) = delete;      \

            
              void operator=(const TypeName&) = delete


            // 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() = delete;                           \

            
              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)))))


            // 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, 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__) && 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
	/*
	* 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.
	#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
	TypeName(const TypeName&) = delete; \
	void operator=(const TypeName&) = delete

	// 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() = delete; \
	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)))))

	// 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, 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__) && 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