As i guess something is wrong with memory allocation. Need help!

[autorius]

My tasks was to write a program which finds difference between two arrays (elements which are in first array but not in second and vice-versa).
Program works, but something wrong is with the memory allocation for array.


My code is:
main.c

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


int main()
{
    int n, m;


    printf("Iveskite pirmo masyvo ilgi: ");
    scanf("%d", &n);


    int *Mas;
    Mas = (int*) malloc (sizeof(int) * n);


    printf("Iveskite pirmo masyvo elementus: ");
    Skaito(Mas, n);


    printf("\n\nIveskite antro masyvo ilgi: ");
    scanf("%d", &m);


    int *Mas_2;
    Mas_2 = (int*) malloc (sizeof(int) * m);


    printf("Iveskite antro masyvo elementus: ");
    Skaito(Mas_2, m);


    Raso(Mas, n);
    Raso(Mas_2, m);


    int *Skirt;
    Skirt = (int*) malloc (sizeof(int));


    int kiek = 0;
    kiek = Skirtumas(Skirt,Mas,Mas_2,n,m,kiek);
    kiek = Skirtumas(Skirt,Mas_2,Mas,m,n,kiek);
    Raso(Skirt,kiek);


    return 0;
}

header.h
function "ar_buvo" checks if certain element is already inserted in difference's array.
function "ar_tinka" checks if certain element meets requirements.
Counts how many certain elements are in first and second arrays then counts difference.
function "Skirtumas" makes difference's array: allocates memory and etc.

#ifndef HEADER_H_INCLUDED
#define HEADER_H_INCLUDED


int ar_buvo (int *A, int kiek, int reiksme);
void Raso (int *A, int kiek);
void Skaito (int *A, int kiek);
int ar_tinka (int reiksme, int *A1, int *A2, int n, int m);
int Skirtumas (int *Skirt, int *A1, int *A2, int A1_ilgis, int A2_ilgis,int kiek);


#endif // HEADER_H_INCLUDED

func.c

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


int ar_buvo (int *A, int kiek, int reiksme)
{
    int i;
    int buvo_nebuvo = 0;
    if (kiek == 0)
    {
        buvo_nebuvo = 0;
    }
    else
    {
        for (i = 0; i < kiek; i++)
        {
            if (reiksme == A[i])
            {
                buvo_nebuvo = 1;
            }
        }
    }
    return buvo_nebuvo;
}


void Raso (int *A, int kiek)
{
    int i;
    for (i = 0; i < kiek; i++)
    {
        printf("%d ",A[i]);
    }
    printf("\n");
}


void Skaito (int *A, int kiek)
{
    int skc, i;
    for (i = 0; i < kiek; i++)
    {
        scanf("%d", &skc);
        A[i] = skc;
    }
}


int Skirtumas (int *Skirt, int *A1, int *A2, int A1_ilgis, int A2_ilgis, int kiek)
{
    int i, j;
    for (i = 0; i < A1_ilgis; i++)
    {
        if (ar_buvo(Skirt, kiek, A1[i])==0)
        {
            int kiek_2 = ar_tinka(A1[i], A1, A2, A1_ilgis, A2_ilgis);
            for (j = kiek; j < (kiek + kiek_2); j++)
            {
                Skirt = (int*) realloc (Skirt, sizeof(int));
                Skirt[j] = A1[i];
            }
            kiek = kiek + kiek_2;
        }
    }
    return kiek;
}


int ar_tinka (int reiksme, int *A1, int *A2, int n, int m)
{
    int kiek = 0;
    int kiek_1 = 0;
    int kiek_2 = 0;
    int i;
    for (i = 0; i < n; i++)
    {
        if (A1[i] == reiksme)
        {
            kiek_1++;
        }
    }
    for (i = 0; i < m; i++)
    {
        if (A2[i] == reiksme)
        {
            kiek_2++;
        }
    }
    if (kiek_1 > kiek_2)
    {
        kiek = kiek_1 - kiek_2;
    }
    else
    {
        kiek = kiek_2 - kiek_1;
    }
    return kiek;
}

[Malcolm McLean]

Skirt = (

int*) realloc (Skirt, sizeof(int));

you need to realloc to the new size of the array, (j+1)*sizeof(int) I think, but I haven't followed the logic closely.

[autorius]

didn't work that :/ any more suggestions?

[AndiPersti]

What didn't work? Show your changes.

Bye, Andreas

[autorius]

so i have made changes like Malcolm said and the program crashes if i input:
as first array: 1 1 1 1 1
as second array: 0 0 0 0 0 0
ahhh... not only crashes. With other tests the results are non-sense

and this is how it looks now:

int Skirtumas (int *Skirt, int *A1, int *A2, int A1_ilgis, int A2_ilgis, int kiek){
    int i, j;
    for (i = 0; i < A1_ilgis; i++)
    {
        if (ar_buvo(Skirt, kiek, A1[i]) == 0)
        {
            int kiek_2 = ar_tinka(A1[i], A1, A2, A1_ilgis, A2_ilgis);
            for (j = kiek; j < (kiek + kiek_2); j++)
            {
                Skirt = (int*) realloc (Skirt, (j+1)*sizeof(int));
                Skirt[j] = A1[i];
            }
            kiek = kiek + kiek_2;
        }
    }
    return kiek;
}

[Salem]

> int Skirtumas (int *Skirt, int *A1, int *A2, int A1_ilgis, int A2_ilgis, int kiek)
...
> Skirt = (int*) realloc (Skirt, (j+1)*sizeof(int));
Are you expecting the caller of this function to receive a possibly moved pointer to the memory you've been realloc'ing?

Because if you are, you need to make some changes.

int Skirtumas (int **Skirt, int *A1, int *A2, int A1_ilgis, int A2_ilgis, int kiek){
    int i, j;
    for (i = 0; i < A1_ilgis; i++)
    {
        if (ar_buvo(*Skirt, kiek, A1[i]) == 0)
        {
            int kiek_2 = ar_tinka(A1[i], A1, A2, A1_ilgis, A2_ilgis);
            for (j = kiek; j < (kiek + kiek_2); j++)
            {
                *Skirt = (int*) realloc (*Skirt, (j+1)*sizeof(int));
                (*Skirt)[j] = A1[i];
            }
            kiek = kiek + kiek_2;
        }
    }
    return kiek;
}

And you need to call it with &mySkirt to pass in a pointer to your pointer.