点 (.) 在结构初始值设定项中是什么意思？

Question

static struct fuse_oprations hello_oper = {
  .getattr = hello_getattr,
  .readdir = hello_readdir,
  .open    = hello_open,
  .read    = hello_read,
};

I don't understand this C syntax well. I can't even search because I don't know the syntax's name. What's that?

Answer 1

This is a C99 feature that allows you to set specific fields of the struct by name in an initializer. Before this, the initializer needed to contain just the values, for all fields, in order -- which still works, of course.

So for the following struct:

struct demo_s {
  int     first;
  int     second;
  int     third;
};

...you can use

struct demo_s demo = { 1, 2, 3 };

...or:

struct demo_s demo = { .first = 1, .second = 2, .third = 3 };

...or even:

struct demo_s demo = { .first = 1, .third = 3, .second = 2 };

...though the last two are for C99 only.

Answer 2

这些是 C99 的指定初始值设定项。

Answer 3

Its known as designated initialisation (see Designated Initializers ). An "initializer-list", Each ' . ' is a " designator " which in this case names a particular member of the ' fuse_oprations ' struct to initialize for the object designated by the ' hello_oper ' identifier.

Answer 4

整个语法被称为 COD3BOY 已经提到的指定初始化程序，它通常用于在声明时需要将结构初始化为某些特定或默认值的情况。