CODEWITHSUNDEEP
cpointers
Steven Oh
Steven Oh

Reputation: 394

Pointer in C gives all zero values

I made a number guessing game and want to print out all of the numbers that the user guessed while playing the game. However, when I run the program, it always prints out zero for all the values.

Your Tries: 0, 0, 0, 0, 0, %

It may be something wrong with the way I assigned the pointer value? Any help would be appreciated

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

int arr_size = 0;

int main()
{
    // Initialize random number with seed 2021.
    // Do not change this line, and do not call srand again.
    srand(2022);

    // the next line generate a random number between 1 to 100

    int n = (rand() % 100) + 1; 
    int *p = malloc(sizeof(int) * arr_size);
    
    while(1){
        
        int guess;
        scanf("%d", &guess);
        
        arr_size ++; 
        p = realloc(p, sizeof(int) * arr_size);
        p[arr_size-1] = guess;
        
        if(n > guess){
            printf("The Number is greater than %d\n", guess);
        }else if(n < guess){
            printf("The Number is less than %d\n", guess);
        }else{
            printf("You win. The Number is %d\n", guess);
            break;
        }
        
        
        
        if(guess == -1){
            printf("You input wrong number\nYou lose. The Number is %d", n);
            break;
        }
        
    }
    
    printf("Your Tries: ");
    for(int i = 0; i < arr_size; i ++){
        printf("%d, ", p[arr_size]);
    }
    
    return 0;
}

Upvotes: 0

Views: 105

Answers (1)

Lundin
Lundin

Reputation: 213678

  • int *p = malloc(sizeof(int) * arr_size);

    Allocating zero bytes isn't safe, the compiler can either return a null pointer or a pointer pointing at weird stuff, which may or may not be reallocatable(?). Replace this with int *p = NULL; to get deterministic, portable behavior instead.

  • p = realloc(p, sizeof(int) * arr_size); There is no guarantee that p is pointing at the reallocated data after this. Correct use of realloc is:

    int* tmp = realloc(p, sizeof(int) * arr_size); 
if(tmp == NULL) { /* handle errors */ }
p = tmp;

  • You never free(p).

  • There is no need to use dynamic allocation to begin with here, all you achieve with it is needless complexity, bloat and a much slower program. Just use int p[100]; and watch all your problems go away, while at the same time massively improving execution speed.

  • printf("%d, ", p[arr_size]); is nonsense and out of bounds, use p[i].

Upvotes: 1

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