Why can an array inside a function be longer than an array inside main function in c?

Question

array[4] is an array of 4 length. Passing array and 4 to function read_line, the array str[] would be an array of 4 length so the array could only hold a character up to str[3], I thought.

#include <stdio.h>

int read_line(char str[], int n);

int main(void)
{
   char array[4];

   read_line(array, 4);

   printf("%s\n", array);

   return 0;
}

int read_line(char str[], int n)
{
    int ch, i = 0;

    while ((ch = getchar()) != '\n')
        if (i < n)             
          str[i++] = ch;
    str[i] = '\0';

    return i;
}

But when I entered four characters like abcd, it runs without any error.

abcd

Why can the array str[] hold '\0' in str[4]?

Undefined behavior. Sometimes it crashes, sometimes it seems to work, but it's always a bug. Use Address Sanitizer to try and catch these sort of issues. https://godbolt.org/z/9xEPxz85x — Retired Ninja, May 17 '22 at 03:46
C doesn't have any kind of bounds checking. You, as the programmer, needs to keep track that the code doesn't go out of bounds of your arrays. — Some programmer dude, May 17 '22 at 03:48
Also note, that as an argument `char str[]` is really the same as `char *str`. — Some programmer dude, May 17 '22 at 03:50

Why can an array inside a function be longer than an array inside main function in c?

0 Answers0