Question

I’m currently working on a school (matrix multiplier) project and I have a problem.

I reprensent a matrix with a 2d array and I allocate it this way :

typedef struct matrix
{
    int** matrix;
    unsigned int l;
    unsigned int c;
} matrix;


int matrix_alloc(matrix** matr, unsigned int l, unsigned int c)
{
    unsigned int i, j;
    *matr = malloc(sizeof(matrix));                             /* Allocate memory for the structure */

    if (*matr == NULL)                                                  /* Check if malloc succeeded             */
    {
        fprintf(stderr, "malloc error");                                        /* If not print error                        */
        return -1;
    }

    (*matr)->matrix = malloc(l*sizeof(int*));           /* Allocate memory for columns of the matrix*/

    if ((*matr)->matrix == NULL)
    {
        fprintf(stderr, "malloc error");
        free(*matr);
        return -1;
    }

    for (i = 0; i < l; i++)
    {
        (*matr)->matrix[i] = malloc(c*sizeof(int));

        if ((*matr)->matrix[i] == NULL)
        {
            fprintf(stderr, "malloc error");

            for (j = 0; j < i; j++)
            {
                free((*matr)->matrix[j]);
            }

            free(*matr);
            return -1;
        }

        for (j = 0; j < c; j++)
        {
            (*matr)->matrix[i][j] = 2; // Matrix should be filled with 2 for tests
            printf("Element added : %d\n", (*matr)->matrix[i][j]);

        }
    }

    (*matr)->l = l;
    (*matr)->c = c;
    printf("will print matrix----------------------\n");
    matrix_print(*matr);
    return 0;
}

And this is how I print the matrix

void matrix_print(matrix* m)
{
    unsigned int i, j;
    int v;
    printf("********************************************************************************\n");
    printf("Lines:\t %i\n", m->l);
    printf("Cols:\t %i\n", m->c);
    printf("Matrix::\n");

    for (i = 0; i < m->l; i++)
    {
        for (j = 0; j < m->c; j++)
        {
            matrix_get_elem_at(v, i, j, m);
            printf("\t%d", v);
            /*printf("\t%ld", mpz_get_si(v)); */
        }

        printf("\n");
    }

    printf("********************************************************************************\n");
}

When I do

     matrix* matr;
       /* alloc matrix */
       assert(matrix_alloc(&matr, 10, 10) == 0);
       printf("----------------------------will print test matrix\n");
       matrix_print(matr);

My matrix is filled with 32767 instead of 2

Can someone help me get rid of this bug?

Thank you

Ben

Answer 1

You should show us more code (for example, how did you declare typedef matrix?) But I bet that the problem is in matrix_get_elem_at – it should get int* for the first parameter. not int.