Compound literals

可以认为等价于匿名数组或者匿名结构体变量。

来看它的一个例子：

    struct proto **proto = (struct proto* []) {
        & ctx->lan, 
        & ctx->wan,
        0,  
    };  
 
    while (*proto) {
        if (setup_proto(*proto) < 0) {
            plog(NETMAN, ERR, "setup proto %s failed", (*proto)->name);
            return -1;                                                                                                                                                                                                           
        }   
        proto++;
    }

某些情况下，可以使编码更简洁。

结构体的例子：

Usually, the specified type is a structure. Assume thatstruct foo and structure are declared as shown:

     struct foo {int a; char b[2];} structure;

Here is an example of constructing a struct foo with a compound literal:

     structure = ((struct foo) {x + y, 'a', 0});

This is equivalent to writing the following:

     {
       struct foo temp = {x + y, 'a', 0};
       structure = temp;
     }

In C, a compound literal designates an unnamed object with static or automatic storage duration.

参考：

https://gcc.gnu.org/onlinedocs/gcc-4.8.0/gcc/Compound-Literals.html

ILD