替换宏变量中的字符串? [英] Replace a string in a macro variable?

问题描述

我有一个宏，我可以在该宏中传递参数，并使用该宏根据输入的名称定义一个新变量:

I have a macro where I pass in an argument and use that define a new variable based on the name of the input:

#define DO_X(x) char _do_x_var_ ## x; /* other things */

问题是，如果我传入一个struct变量，它会中断:

The problem is if I pass in a struct variable, it breaks:

DO_X(some_struct->thing)

成为:

char _do_x_var_some_struct->thing; /* other things */

我希望它评估为:

char _do_x_var_some_struct__thing; /* other things */

(或任何与输入内容相似的有效变量名)

(or any valid variable name containing something similar to the input)

我真正想要的是使它们起作用:

What I actually want is for these to work:

#define DO_X(x) for(char _do_x_var_ ## x; /*things*/)
DO_X(x){
    DO_X(y) {
        /*things*/
    }
}

DO_X(object->x){
    DO_X(object->y) {
        /*things*/
    }
}

但是这些失败了:

#define DO_X(x) for(char _do_x_var_ ## x; /*things*/)
DO_X(x){
    DO_X(x) { // <-- multiple definition of _do_x_var_x
        /*things*/
    }
}

DO_X(object->x){
    DO_X(object->x) { // <-- multiple definition of _do_x_var_object__x (or whatever)
        /*things*/
    }
}

有什么办法可以使这项工作成功吗?也许用__替换->或其他?我找到了串联的方法，但没有替换字符串的方法.

Is there some way to make this work? Maybe replacing -> with __ or something? I've found ways to concatenate, but not replace strings..

推荐答案

您尚未找到重写任意字符串的方法，因为宏无法做到这一点.宏名称必须是有效的标识符，而->则不是. C预处理器的功能非常有限.您可以研究m4以获得更强大的预处理器，但您可能走错了路.

You haven't found a way to rewrite arbitrary strings because macros cannot do that. Macros names have to be valid identifiers, which -> is not. The C preprocessor is very limited in what it can do. You could look into m4 for a stronger preprocessor, but you're likely headed down the wrong road.

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