verdnatura-chat/ios/Pods/Folly/folly/Preprocessor.h

161 lines
5.1 KiB
C++

/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* 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.
*/
// @author: Andrei Alexandrescu
#pragma once
#include <folly/CPortability.h>
/**
* Necessarily evil preprocessor-related amenities.
*/
// MSVC's preprocessor is a pain, so we have to
// forcefully expand the VA args in some places.
#define FB_VA_GLUE(a, b) a b
/**
* FB_ONE_OR_NONE(hello, world) expands to hello and
* FB_ONE_OR_NONE(hello) expands to nothing. This macro is used to
* insert or eliminate text based on the presence of another argument.
*/
#define FB_ONE_OR_NONE(a, ...) FB_VA_GLUE(FB_THIRD, (a, ##__VA_ARGS__, a))
#define FB_THIRD(a, b, ...) __VA_ARGS__
/**
* Helper macro that extracts the first argument out of a list of any
* number of arguments.
*/
#define FB_ARG_1(a, ...) a
/**
* Helper macro that extracts the second argument out of a list of any
* number of arguments. If only one argument is given, it returns
* that.
*/
#ifdef _MSC_VER
// GCC refuses to expand this correctly if this macro itself was
// called with FB_VA_GLUE :(
#define FB_ARG_2_OR_1(...) \
FB_VA_GLUE(FB_ARG_2_OR_1_IMPL, (__VA_ARGS__, __VA_ARGS__))
#else
#define FB_ARG_2_OR_1(...) FB_ARG_2_OR_1_IMPL(__VA_ARGS__, __VA_ARGS__)
#endif
// Support macro for the above
#define FB_ARG_2_OR_1_IMPL(a, b, ...) b
/**
* Helper macro that provides a way to pass argument with commas in it to
* some other macro whose syntax doesn't allow using extra parentheses.
* Example:
*
* #define MACRO(type, name) type name
* MACRO(FB_SINGLE_ARG(std::pair<size_t, size_t>), x);
*
*/
#define FB_SINGLE_ARG(...) __VA_ARGS__
#define FOLLY_PP_DETAIL_APPEND_VA_ARG(...) , ##__VA_ARGS__
/**
* Helper macro that just ignores its parameters.
*/
#define FOLLY_IGNORE(...)
/**
* Helper macro that just ignores its parameters and inserts a semicolon.
*/
#define FOLLY_SEMICOLON(...) ;
/**
* FB_ANONYMOUS_VARIABLE(str) introduces an identifier starting with
* str and ending with a number that varies with the line.
*/
#ifndef FB_ANONYMOUS_VARIABLE
#define FB_CONCATENATE_IMPL(s1, s2) s1##s2
#define FB_CONCATENATE(s1, s2) FB_CONCATENATE_IMPL(s1, s2)
#ifdef __COUNTER__
// Modular builds build each module with its own preprocessor state, meaning
// `__COUNTER__` no longer provides a unique number across a TU. Instead of
// calling back to just `__LINE__`, use a mix of `__COUNTER__` and `__LINE__`
// to try provide as much uniqueness as possible.
#if FOLLY_HAS_FEATURE(modules)
#define FB_ANONYMOUS_VARIABLE(str) \
FB_CONCATENATE(FB_CONCATENATE(FB_CONCATENATE(str, __COUNTER__), _), __LINE__)
#else
#define FB_ANONYMOUS_VARIABLE(str) FB_CONCATENATE(str, __COUNTER__)
#endif
#else
#define FB_ANONYMOUS_VARIABLE(str) FB_CONCATENATE(str, __LINE__)
#endif
#endif
/**
* Use FOLLY_PP_STRINGIZE(x) when you'd want to do what #x does inside
* another macro expansion.
*/
#define FOLLY_PP_STRINGIZE(x) #x
#define FOLLY_PP_DETAIL_NARGS_1(dummy, _7, _6, _5, _4, _3, _2, _1, _0, ...) _0
#define FOLLY_PP_DETAIL_NARGS(...) \
FOLLY_PP_DETAIL_NARGS_1(dummy, ##__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1, 0)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_0(fn, ...)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_1(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_0(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_2(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_1(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_3(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_2(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_4(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_3(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_5(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_4(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_6(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_5(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_REC_7(fn, a, ...) \
fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_6(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_2(fn, n, ...) \
FOLLY_PP_DETAIL_FOR_EACH_REC_##n(fn, __VA_ARGS__)
#define FOLLY_PP_DETAIL_FOR_EACH_1(fn, n, ...) \
FOLLY_PP_DETAIL_FOR_EACH_2(fn, n, __VA_ARGS__)
/**
* FOLLY_PP_FOR_EACH
*
* Used to invoke a preprocessor macro, the name of which is passed as the
* first argument, once for each subsequent variadic argument.
*
* At present, supports [0, 8) arguments.
*
* This input:
*
* #define DOIT(a) go_do_it(a);
* FOLLY_PP_FOR_EACH(DOIT, 3, 5, 7)
* #undef DOIT
*
* Expands to this output (with whitespace adjusted for clarity):
*
* go_do_it(3);
* go_do_it(5);
* go_do_it(7);
*/
#define FOLLY_PP_FOR_EACH(fn, ...) \
FOLLY_PP_DETAIL_FOR_EACH_1( \
fn, FOLLY_PP_DETAIL_NARGS(__VA_ARGS__), __VA_ARGS__)