为什么函数printk()不使用逗号分隔参数? [英] Why doesn't the function printk() use a comma to separate parameters?

问题描述

一个示例 printk 调用:

printk(KERN_INFO "Log message.\n");

也许这个问题通常与C有关，因为在用逗号分隔参数之前，我从未见过C中的函数.

Perhaps this question is more about C in general, because I've never seen a function in C before that separated parameters without a comma.

这是如何工作的?编译器如何处理此信息?由于日志级别是整数，并且消息是指向char数组的指针，因此必须分别传递它们.

How does this work? What does the compiler do with this information? Since the log level is an integer and the message is a pointer to a char array, it must pass them separately.

推荐答案

printk()函数仅采用一个 const char * 参数. KERN_INFO 宏扩展为"\ 001""6" ，产生:

The printk() function only takes one const char* argument. The KERN_INFO macro expands to "\001" "6", yielding:

printk("\001" "6" "Log message.\n");

C词法分析器连接相邻的字符串文字标记，这意味着上面的内容转换为:

The C lexer concatenates adjacent string literal tokens which means that the above is converted into:

printk("\0016Log message.\n");

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