C 数组的范围初始化 [英] Range Initialization of a C Array

问题描述

非常简单的问题，在哪里这段代码在哪里工作?

Very simple question of where does this code work?

static void *gostruct[] = 
{
    [0 ... 255] = &&l_bad,
    ['	'] = &&l_loop, [' '] = &&l_loop, ['
'] = &&l_loop, ['
'] = &&l_loop,
    ['"'] = &&l_qup,
    [':'] = &&l_loop,[','] = &&l_loop,
    ['['] = &&l_up, [']'] = &&l_down, // tracking [] and {} individually would allow fuller validation but is really messy
    ['{'] = &&l_up, ['}'] = &&l_down,
    ['-'] = &&l_bare, [48 ... 57] = &&l_bare, // 0-9
    ['t'] = &&l_bare, ['f'] = &&l_bare, ['n'] = &&l_bare // true, false, null
};

通读它可以清楚地看到它将包含 256 个条目的数组初始化为值 &&l_bad，然后用特定值覆盖某些索引.但是这段代码不能在我可以访问的 VS2010 中编译，所以我想知道这是有效的 C 代码.

Reading through it its clear to see that it initializes an array containing 256 entries to the value &&l_bad and then overrides certain indexes with specific values. But this code does not compile in VS2010 which is what I have access to so I am wondering where this is valid C code.

注意:此代码片段取自 github 上的 JSON 解析器 据我了解，它创建了用于处理 JSON 字符串的跳转表.

NOTE: This code snippet was taken from a JSON parser on github that, from my understanding, creates jump tables for the processing of JSON strings.

推荐答案

这个结构叫做 指定初始化器.
在指定初始化器中使用 Range 是 GNU gcc 特定的扩展.

This construct is called Designated Initializers.
Using Range in Designated Initializers is a GNU gcc specific extension.

要将一系列元素初始化为相同的值，请编写 [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 };

用 -pedantic 编译它会告诉你.
请注意，它是不可移植的，因为它是特定于编译器的扩展.

Compiling it with -pedantic shall tell you so.
Note that it is non-portable since it is a compiler specific extension.

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