CODEWITHSUNDEEP
carraysdynamic-memory-allocation
OldTeaOwl
OldTeaOwl

Reputation: 245

Error in filling static array dynamically in C

I have to use a static two-dimensional array and a dynamic matrix as a part of my college task. So, I've created them, and now trying to fill and then print them to a console, but getting "segmentation fault". That's how I'm trying to achieve it:

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

#define ROWS 5
#define COLUMNS 7

int main3() {
    /*init static array*/
    double twodimarray[ROWS][COLUMNS];

    /*init dynamic array*/
    double **matrix = (double**) malloc(sizeof(double*) * ROWS);
    for(int i = 0; i < ROWS; i++) *(matrix + i) = (double*)malloc(sizeof(double) * COLUMNS);

    for(int i = 0; i < ROWS; i++){
        dfillarran(*(matrix + i), COLUMNS);
        dfillarran(twodimarray[i], COLUMNS);
    }

    puts("Dynamic matrix :");
    printmx(matrix, ROWS,COLUMNS);

    puts("Static array:");
    printmx(twodimarray, ROWS, COLUMNS);

    /*freeing mem*/
    for(int i = 0; i < ROWS; i++) free(*(matrix + i));
    free(matrix);
}

Error is definitely in function printmx(), but I can't understand why; It works for dynamic matrix, and fails only for static one, but static array name - is a pointer to array of pointers, where each one is pointing array of values, just like dynamic one!
There is code of my printmx() function from arrayutils.h: 

/**Print Matrix*/
void printmx(double** mx, int rows, int col){
    for(int i = 0; i < rows; i++) {
        for(int j = 0; j < col; j++){
            printf("%.lf ", *(*(mx + i)+j));
        }
        putchar('\n');
    }
    putchar('\n');
}

Funcion that fills arrays with random values can be found here, in arrayutils.c, that I've created for all other tasks that use same functions like filling and printing arrays, but I don't think, that problem is there..
Probably, I'm wrong somewhere in theory, and still not getting the difference between static and dynamic matrix, please correct me :)

p.s.There is a screenshot of the error: there is an error

Upvotes: 1

Views: 81

Answers (1)

Vlad from Moscow
Vlad from Moscow

Reputation: 311038

The function printmx may not be called for the two objects of different types.

The array twodimarray is a two dimensional array that when is passed to the function has the type double ( * )[COLUMNS].

While matrix is a pointer of the type double **.

Upvotes: 3

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