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

问题描述

很简单的问题，该代码在在哪里起作用?

Very simple question of where does this code work?

static void *gostruct[] = 
{
    [0 ... 255] = &&l_bad,
    ['\t'] = &&l_loop, [' '] = &&l_loop, ['\r'] = &&l_loop, ['\n'] = &&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初始化了一个包含256个条目的数组，该数组包含&& l_bad值，然后用特定值覆盖某些索引.但是此代码无法在VS2010中编译，这是我可以访问的，所以我想知道这在哪里是有效的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:此代码段摘自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

此结构称为

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 };

使用-pedantic进行编译将告诉您.
请注意，它是不可移植的，因为它是编译器特定的扩展.

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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