CODEWITHSUNDEEP
c
Melvin
Melvin

Reputation: 35

Infinite loop - what is happening?

I have the following code in C which is supposed to return a 4-bit binary representation of every number in a 8-digit long string of numbers. For some reason it's looping infinitely now.

The current output looks like this (with 12345677 as input): 0001 0010 0011 0000 0000 0000 0000 0000 0000 ... (endless zeroes). As you can see the first 3 numbers work (which I think is very odd).

What is going wrong here?

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

    #define LENGTH 8

    int main()
    {
        char number[LENGTH];

        printf("Geef nummers in : ");
        scanf("%s", number);   

        printf("Resultaat : ");

        for(int i=0; i<LENGTH; i++) {

          char re[4];

          re[3] = ((number[i]) & 1) ? '1' : '0';
          number[i] >>= 1;
          re[2] = ((number[i]) & 1) ? '1' : '0';
          number[i] >>= 1;
          re[1] = ((number[i]) & 1) ? '1' : '0';
          number[i] >>= 1;
          re[0] = ((number[i]) & 1) ? '1' : '0';
          number[i] >>= 1;
          re[4] = '\0';

          int res = atoi(re);
          printf("%04d ", res);

        }  

        printf("\n");
    }

Upvotes: 0

Views: 142

Answers (2)

Jim Buck
Jim Buck

Reputation: 20734

You only declare 4 elements for re (0 through 3 inclusive) but you use a 5th element when doing re[4]. You are invoking undefined behavior at that point. You need to define re as:

char re[5];

Upvotes: 3

0xF1
0xF1

Reputation: 6116

You are accessing over the bounds of array re, by assigning value to re[4].

As Jim Buck said, use char re[5], or use index 3 as the last one for array re.

Upvotes: 0

Related Questions