是否可以使用变量声明数组？

Question

Hi I was told during my first class about arrays in C that you cannot declare them using a variable, for example: int array[n] . Yet if I write a code like this:

#include <stdio.h>
int main()
{
    int n;
    scanf("%d",&n);
    int array[n];
}

Codeblocks doesn't give me any warning or error. How do I know that what I wrote isn't correct?

Answer 1

This is valid (since C99), although optional (since C11). More portable:

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
  size_t n = 0;
  int *array = NULL;
  if ((scanf("%zu", &n) <= 0) ||
      (n > SIZE_MAX / sizeof(*array)) ||
      ((array = malloc(n * sizeof(*array))) == NULL)) 
  {
    return EXIT_FAILURE;
  }

  // Use array

  free(array);  // Don't forget to free the memory.
}

Answer 2

Codeblocks doesn't give you an error or a warning, because there is none. You can do the declaration with no problem since C99.