Segmentation Fault with Pointers in Returning pointer to array C

Question

I am trying to solve a problem (given the current code skeleton) and having trouble with pointers. I am getting a segmentation fault at the printf("%d", result[result_i]); statement in the following code:

#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int* solve(int a0, int a1, int a2, int b0, int b1, int b2, int *result_size){
    // Complete this function
    *result_size = 2;
    int* scores[*result_size];

    *scores[0] = ((a0>b0)?1:0)+ ((a1>b1)?1:0)+ ((a2>b2)?1:0);
    *scores[1] = ((a0<b0)?1:0)+ ((a1<b1)?1:0)+ ((a2<b2)?1:0);

    return *scores;
}

int main() {
    int a0; 
    int a1; 
    int a2; 
    scanf("%d %d %d", &a0, &a1, &a2);
    int b0; 
    int b1; 
    int b2; 
    scanf("%d %d %d", &b0, &b1, &b2);
    int result_size;
    int* result = solve(a0, a1, a2, b0, b1, b2, &result_size);
    for(int result_i = 0; result_i < result_size; result_i++) {
        if(result_i) {
            printf(" ");
        }
        printf("%d", result[result_i]);
    }
    puts("");


    return 0;
}

I am not sure what I'm doing wrong with assigning the pointers within the solve() function (as well as returning the pointer to the array within the same function). I would like to know what part I am doing wrong when pointing and assigning different values from said pointer. Thanks.

Possible duplicate of How to access a local variable from a different function using pointers? — John3136
– John3136, Commented Feb 18, 2018 at 22:39

elMentat · Accepted Answer · 2018-02-18 23:27:13Z

1

Your int* solve function may be the problem.

After allocating memory instead for this array, it should solve the problem.

int* solve(int a0, int a1, int a2, int b0, int b1, int b2, int *result_size){
    // Complete this function
    *result_size = 2;
    int* scores = malloc(sizeof(int) * (*result_size));

    scores[0] = ((a0>b0)?1:0)+ ((a1>b1)?1:0)+ ((a2>b2)?1:0);
    scores[1] = ((a0<b0)?1:0)+ ((a1<b1)?1:0)+ ((a2<b2)?1:0);

    return scores;
}

and at the bottom of int main() it is good practice to free the array:

free(result);

answered Feb 18, 2018 at 23:27

elMentat

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1 Comment

qxzsilver Over a year ago

Thank you very much for clearing this up! I understand now I need to allocate the memory of an (int) per each cell for an array in C.

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