为什么一个人需要两个方括号才能在C中使用宏? [英] Why one needs two brackets to use macros in C?

问题描述

    KdPrint(("Enter HelloWDMAddDevice\n"));

这样做的原因是什么?

推荐答案

因此，您可以将整个参数列表传递给宏，然后将其传递给带有可变数量参数的函数.

That is so you can pass an entire argument list to the macro and have it pass it on to a function that takes a variable number of arguments.

我敢打赌该宏的定义是:

I would bet anything that the definition of that macro is:

#if DEBUG /* or something like it */
#define KdPrint(args) (printf args)
#else
#define KdPrint(args) /* empty */
#endif

或与其他功能类似，类似于printf.

Or similar to some other function that works just like printf.

如果将其定义为printf(args)，则只能传递单个字符串参数，因为宏的参数不能包含不在嵌套括号内的逗号.

If it were defined as printf(args), then you could only pass the single string argument, because an argument to a macro can't contain a comma that isn't inside a nested parenthesis.

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