C:这个宏是什么意思? [英] C: What does this macro mean?

问题描述

您如何阅读此宏的第二行? (*)0在这种情况下是什么意思?

How do you read the second line of this macro? What does (type *)0 mean in this context?

#define container_of(ptr, type, member) ({ \
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})

推荐答案

您正在找到((type *)0)->member的类型.它实际上并没有取消引用指针(我告诉你这将是疯狂.疯狂！)

You're finding the type of ((type *)0)->member. It's not actually dereferencing the pointer (that would be madness, I tell you. Madness!)

这是C的怪异之处.也许如果他们写typeof(type.member)会更有意义，但遗憾的是这是不允许的.

It's a weirdness of C. Maybe it would make more sense if they wrote typeof(type.member) but sadly that is not allowed.

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