kopia lustrzana https://github.com/espressif/esp-idf
47 wiersze
2.0 KiB
C
47 wiersze
2.0 KiB
C
/*
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* SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#pragma once
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/*
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This header contains various general purpose helper macros used across ESP-IDF
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*/
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Macro to select different versions of other macros based on whether VA_ARGS has an argument or no argument
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*
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* Some macros (such as in FreeRTOS) have two versions (one that accepts arguments and another that does not). The
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* following "CHOOSE_MACRO_VA_ARG" selector allows automatic selection between two different versions of a macro.
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*
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* "CHOOSE_MACRO_VA_ARG" make use of the fact that "##__VA_ARGS__," will eliminate the trailing comma if there are no
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* arguments, thus allows subsequent arguments in "CHOOSE_MACRO_VA_ARG" to be left shifted in the parameter list.
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* Therefore, if we call "CHOOSE_MACRO_VA_ARG(_0, ##__VA_ARGS__, MACRO1, MACRO2)(__VA_ARGS__)", the result will be:
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*
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* - MACRO1(__VA_ARGS__) if __VA_ARGS__ was not empty
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* - MACRO2() if __VA_ARGS__ was empty
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*
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* @note In the future, we want to switch to C++20. We also want to become compatible with clang. Hence, we provide two
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* versions of the following macros which are using variadic arguments. The first one is using the GNU extension
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* ##__VA_ARGS__. The second one is using the C++20 feature __VA_OPT__(,). This allows users to compile their code with
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* standard C++20 enabled instead of the GNU extension. Below C++20, we haven't found any good alternative to using
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* ##__VA_ARGS__.
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*/
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#if defined(__cplusplus) && (__cplusplus > 201703L)
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#define CHOOSE_MACRO_VA_ARG(_0 __VA_OPT__(,) __VA_ARGS__, MACRO, ...) MACRO
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#else
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#define CHOOSE_MACRO_VA_ARG(_0, _1, MACRO, ...) MACRO
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#endif
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_Static_assert(CHOOSE_MACRO_VA_ARG(_0, x, 0, 1) == 0, "CHOOSE_MACRO_VA_ARG() result does not match for 0 arguments");
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_Static_assert(CHOOSE_MACRO_VA_ARG(_0, 0, 1) == 1, "CHOOSE_MACRO_VA_ARG() result does not match for 1 argument");
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#ifdef __cplusplus
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}
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#endif
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