C中的大小写可变参数宏 [英] Case variadic macro in C

问题描述

我有2个包装器宏，用于声明函数输入参数:

I have 2 wrapper macros for asserting function input parameters:

/**
 * @brief   An assert wrapper with no value return in case assert fails.
 * @param   x_: value to test for being non zero.
 */
#define UTIL_ASSERT_VOID(x_)                                                \
    assert_param(x_);                                                       \
    if (!x_)                                                                \
        return;                                                             \

/**
 * @brief   An assert wrapper with a value return in case assert fails.
 * @param   x_: value to test for being non zero.
 */
#define UTIL_ASSERT_VAL(x_, ret_)                                           \
    assert_param(x_);                                                       \
    if (!x_)                                                                \
        return ret_;                                                        \

前者用于返回void的函数，而后者则用于返回non-void的函数.我想知道在C11(或更早版本)中是否存在一种机制，该机制仅允许使用带有可变参数数量的单个宏.根据提供给宏的参数数量(1或2)，将编译return或return ret_.

The former is used in functions returning void, while the latter in functions returning non-void. I was wondering either in C11 (or earlier) there is a mechanism allowing one to use only a single macro with variadic parameters amount. Depending on how many parameters are provided to the macro (1 or 2), a return or return ret_ would be compiled.

推荐答案

您可以这样做:

#define UTIL_ASSERT(x_, ...)                                                \
    assert_param(x_);                                                       \
    if (!x_)                                                                \
        return __VA_ARGS__;

但是请记住，您不能保证在此可变参数宏中仅包含1个参数，因此您需要正确使用它.

But remember, you cannot guarantee just 1 parameter in this variadic macro, so you need to use it correctly.

更新: 多亏了此线程，我才有了更好的方法:

Update: Thanks to this thread, I came to better approach:

void assert_param(int x);

#define UTIL_ASSERT_1(x_)   do { assert_param(x_); if (!x_) return; } while(0)

#define UTIL_ASSERT_2(x_, ret_)   do { assert_param(x_); if (!x_) return ret_; } while(0)     

#define GET_MACRO(_1,_2,NAME,...) NAME
#define UTIL_ASSERT(...) GET_MACRO(__VA_ARGS__, UTIL_ASSERT_2, UTIL_ASSERT_1)(__VA_ARGS__)


int foo() {
     UTIL_ASSERT(0,1);
}

void doo() {
     UTIL_ASSERT(0);
}

这比以前的要好得多，因为它以某种方式验证了参数的数量.

This one is much better than previous one, because it somehow validates number of parameters.

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