有没有办法强制C预处理器在宏之前评估宏参数(Is there a way to force C preprocessor to evaluate macro arguments before the

有没有办法强制C预处理器在宏之前评估宏参数(Is there a way to force C preprocessor to evaluate macro arguments before the macro)

我在表单中有许多宏

#define F(A,B) Some function of A and B

为了便于阅读，我想为这些宏定义参数，例如

#define C A,B

所以我可以说

F(C)

但预处理器试图在C之前扩展F并抱怨F需要2个参数。 有没有办法让它在扩展F之前扩展C，以便不会发生错误？

I have a number of macros in the form

#define F(A,B) Some function of A and B

and for readability I would like to define arguments for these macros e.g.

#define C A,B

so that I can say

F(C)

but the preprocessor tries to expand F before C and complains that F needs 2 arguments. Is there a way to make it expand C before it expands F so that the error does not occur?

最满意答案

您可以使用带有可变数量参数的中间宏：

#define F1(A,B) #define F(...) F1(__VA_ARGS__) #define C A,B int main(void) { F(C) F(1,2) return 0; }

这应该编译。 如果传递多于或少于两个参数，或者没有扩展到两个参数的参数，您仍会遇到编译失败。

You can use an intermediate macro that takes a variable number of arguments:

#define F1(A,B) #define F(...) F1(__VA_ARGS__) #define C A,B int main(void) { F(C) F(1,2) return 0; }

This should compile. You will still get a compilation failure if you pass more or less than two arguments, or arguments that don't expand to exactly two arguments.