如何创建一个可变宏(可变参数数)

I want to write a macro in C that accepts any number of parameters, not a specific number

我想在C中写一个宏，它接受任意数量的参数，而不是一个特定的数字。

example:

例子:

#define macro( X )  something_complicated( whatever( X ) )

where X is any number of parameters

X是多少个参数

I need this because whatever is overloaded and can be called with 2 or 4 parameters.

我需要这个，因为任何重载的东西都可以用2或4个参数调用。

I tried defining the macro twice, but the second definition overwrote the first one!

我尝试了两次定义宏，但是第二个定义覆盖了第一个定义!

The compiler I'm working with is g++ (more specifically, mingw)

我所使用的编译器是g++(更确切地说，是mingw)

5 个解决方案

#1

249

C99 way, also supported by VC++ compiler.

C99方式，也支持vc++编译器。

#define FOO(fmt, ...) printf(fmt, ##__VA_ARGS__)

#2

__VA_ARGS__ is the standard way to do it. Don't use compiler-specific hacks if you don't have to.

__VA_ARGS__是标准的方法。如果没有必要，不要使用特定于编译器的技巧。

I'm really annoyed that I can't comment on the original post. In any case, C++ is not a superset of C. It is really silly to compile your C code with a C++ compiler. Don't do what Donny Don't does.

我真的很生气，因为我不能对原帖发表评论。无论如何，c++不是C的超集，使用c++编译器编译C代码是非常愚蠢的。不要做唐尼不做的事。

#3

I don't think that's possible, you could fake it with double parens ... just as long you don't need the arguments individually.

我认为这是不可能的，你可以用双引号来伪装……只要您不需要单独的参数。

#define macro(ARGS) some_complicated (whatever ARGS)
// ...
macro((a,b,c))
macro((d,e))

#4

#define DEBUG

#ifdef DEBUG
  #define PRINT print
#else
  #define PRINT(...) ((void)0) //strip out PRINT instructions from code
#endif 

void print(const char *fmt, ...) {

    va_list args;
    va_start(args, fmt);
    vsprintf(str, fmt, args);
        va_end(args);

        printf("%s\n", str);

}

int main() {
   PRINT("[%s %d, %d] Hello World", "March", 26, 2009);
   return 0;
}

If the compiler does not understand variadic macros, you can also strip out PRINT with either of the following:

如果编译器不理解可变宏，您也可以用以下任何一种方法去除打印:

#define PRINT //

或

#define PRINT if(0)print

The first comments out the PRINT instructions, the second prevents PRINT instruction because of a NULL if condition. If optimization is set, the compiler should strip out never executed instructions like: if(0) print("hello world"); or ((void)0);

第一个注释打印指令，第二个禁止打印指令，因为一个空if条件。如果设置了优化，编译器应该去掉从未执行过的指令，如:If(0)打印(“hello world”);或(0)(空白);

#5

explained for g++ here, though it is part of C99 so should work for everyone

这里解释为g++，虽然它是C99的一部分，所以应该对每个人都适用

http://www.delorie.com/gnu/docs/gcc/gcc_44.html

quick example:

简单的例子:

#define debug(format, args...) fprintf (stderr, format, args)

#1

249