声明数组与变量 [英] Declare an array with a variable

问题描述

我相信数组的大小应该是恒定的INT，当你把它声明。
不过，我整理了以下code，并没有得到任何错误。
能否谈谈这个解释？

I believe that size of the array should be a constant int when you declare it. However, I compiled the following code and it did not get any error. Could you explain about this?

#include <stdio.h>

void function(int);

int main(void){
  int m = 0;
  scanf("%d", &m);
  function(m);
  return 0;
}

void function(int i){
  int array[i];
}

输入：5
输出：无。但没有得到错误。

input: 5 output: nothing. but got no error.

推荐答案

从C99增加了一个可变长度的数组（或VLA）是自动存储时间的数组，其长度在运行时（而不是在编译确定时间）。

Added from C99 a variable-length array (or VLA) is an array data structure of automatic storage duration whose length is determined at run time (instead of at compile time).

VLA工作通过将阵列中的堆栈。这使得分配和访问速度极快，但堆栈通常是小（几KB的），而当VLA溢出栈，它是从无限递归没有什么区别。

VLA works by placing the array in the stack. This makes allocation and access extremely fast, but the stack is usually small (of a few KB), and when the VLA overflows the stack, it's indistinguishable from an infinite recursion.

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