[N ... M]在C聚合初始化程序中是什么意思? [英] What does [ N ... M ] mean in C aggregate initializers?

问题描述

来自 sys.c 123行:

void *sys_call_table[__NR_syscalls] = 
{
    [0 ... __NR_syscalls-1] = sys_ni_syscall,
#include <asm/unistd.h>
};

sys_call_table是数组的通用指针，我可以看到.但是，表示法是什么:

sys_call_table is a generic pointer to arrays, I can see that. However what is the notation:

[0 ... __NR_syscalls-1]

什么是...?

我在这里学到了另一个C技巧:#include <asm/unistd.h>将被预处理，并替换为其内容并分配给[0 ... _NR_syscalls-1].

I learned another C trick here: #include <asm/unistd.h> will be preprocessed and replaced with its content and assigned to [0 ... _NR_syscalls-1].

推荐答案

使用 指定的初始化器 .

It is initialization using Designated Initializers.

基于范围的初始化是gnu gcc扩展.

The range based initialization is a gnu gcc extension.

要将一系列元素初始化为相同的值，请写入[first ... last] = value.这是一个GNU扩展.例如

To initialize a range of elements to the same value, write [first ... last] = value. This is a GNU extension. For example,

 int widths[] = { [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 };

它不是便携式的.使用-pedantic进行编译时会告诉您.

It is not portable. Compiling with -pedantic with tell you so.

在这里如何工作?
预处理器将它的实际内容替换为#include <asm/unistd.h>(它定义了其他符号常量和类型，并声明了其他函数)，这是基于范围的构造，然后将其进一步用于初始化指针数组.

How does it work here?
The preprocessor replaces #include <asm/unistd.h> with its actual contents(it defines miscellaneous symbolic constants and types, and declares miscellaneous functions) in the range based construct, which are then further used for initializing the array of pointers.

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