C Random Number generator returning address

May 24, 2022

A part of my code is to randomly generate an array with numbers between 0 and 999. I do this with a random number generator. However everytime it does it and returns the array, the intArray[8] to intArray[12] have what I presume is the address. How can I fix this. I have printed each part of the array in the randomArr function and they are fine.

Code

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include<time.h>
#include "sorting.h"


void initRandom()
{
    srand(time(NULL));
}

int random(int low, int high)
{
    int number = -1;

    if(low <= high)
    {
        number = (rand() % (high-low+1)) + low;
    }

    return number;
}

void randomArr(int* numArray, int intNum){
    int j = 0;
    initRandom();
    for (j = 0; j < intNum; j++){
        numArray[j] = random(0, 999);
    }
} 

int main(int argc, char* argv[]){
    int* intArray = (int*)malloc(sizeof(double));
    if (argc < 2){
        printf("Error! Not enough arguments!");
    } else if (argc > 3){
        printf("Error! Too many arguments!");
    } else{
        int intNum, i;

        if (argc == 2){
            printf("Please specify number of integers: ");
            scanf("%d", &intNum);
            randomArr(intArray, intNum);

        }
        for (i = 0; i < intNum; i++){
            printf("Num %d: %d\n", i+1, intArray[i]);
        }
    }
    free(intArray);
    return 0;
}

One output example with 20 ints is:

./sorting 1
Please specify number of integers: 20
Num 1: 97
Num 2: 971
Num 3: 579
Num 4: 223
Num 5: 905
Num 6: 883
Num 7: 711
Num 8: 757
Num 9: 544044366
Num 10: 891304505
Num 11: 858863928
Num 12: 842609462
Num 13: 2610
Num 14: 283
Num 15: 568
Num 16: 319
Num 17: 426
Num 18: 443
Num 19: 848
Num 20: 572

>Solution :

the int* intArray = (int*)malloc(sizeof(double)); is allocating a memory buffer of a single sizeof(double) (typically 4 or 8 bytes). Ive changed that to int* intArray = (int*)malloc(sizeof(int) * intNum); to malloc the amount of ints you are going to store. To do that i moved the malloc down into the if statement and moved the free up into the same if statement.

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


void initRandom()
{
    srand(time(NULL));
}

int random(int low, int high)
{
    int number = -1;

    if (low <= high)
    {
        number = (rand() % (high - low + 1)) + low;
    }

    return number;
}

void randomArr(int* numArray, int intNum) {
    int j = 0;
    initRandom();
    for (j = 0; j < intNum; j++) {
        numArray[j] = random(0, 999);
    }
}

int main(int argc, char* argv[]) {
    
    if (argc < 2) {
        printf("Error! Not enough arguments!");
    }
    else if (argc > 3) {
        printf("Error! Too many arguments!");
    }
    else {
        int intNum, i;

        if (argc == 2) {
            printf("Please specify number of integers: ");
            scanf("%d", &intNum);
            int* intArray = (int*)malloc(sizeof(int) * intNum);
            randomArr(intArray, intNum);

            for (i = 0; i < intNum; i++) {
                printf("Num %d: %d\n", i + 1, intArray[i]);
            }
            free(intArray);
        }
    }
    
    return 0;
}

output:

Please specify number of integers: 20
Num 1: 218
Num 2: 837
Num 3: 797
Num 4: 190
Num 5: 555
Num 6: 644
Num 7: 158
Num 8: 673
Num 9: 837
Num 10: 963
Num 11: 936
Num 12: 101
Num 13: 721
Num 14: 257
Num 15: 541
Num 16: 941
Num 17: 285
Num 18: 958
Num 19: 591
Num 20: 971