Матрица. Поиск и замена по колонкам

#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <stdlib.h>
#include <locale.h>
#include <time.h>

#define LEFT -25
#define RIGTH 75

int __cdecl random_matrix(int **, const size_t, const size_t, const int _left, int _rigth);
void __cdecl show_matrix(int **, const size_t, const size_t);
int __cdecl is_positive_column(int **, const size_t, const size_t);
void __cdecl delete_matrix(int **, size_t);
int ** __cdecl create_matrix(int **, const size_t, const size_t);
void resign(int **, const size_t, const size_t);

int main() {
    size_t rows, cols, index;
    int is_positive = 0;
    int ** matrix = NULL;

    setlocale(LC_CTYPE, "Russian_Russia.1251");
    printf("Введите строки: ");
    scanf_s("%i", &rows);
    printf("Введите столбцы: ");
    scanf_s("%i", &cols);

    srand((unsigned)time(NULL));
    matrix = create_matrix(matrix, rows, cols);

    if (random_matrix(matrix, rows, cols, LEFT, RIGTH)) {
        printf("Исходная матрица:\n");
        show_matrix(matrix, rows, cols);

        for (index = 0; index < cols; index++) {
            if (is_positive = is_positive_column(matrix, rows, index)) {
                if (index)
                    resign(matrix, rows, index - 1);
                break;
            }

            if (is_positive && !index) break;
        }

        printf("Изменённая матрица:\n");
        show_matrix(matrix, rows, cols);
    }

    delete_matrix(matrix, rows);
    _getch();
}
int random_matrix(int ** _matrix, const size_t _rows, const size_t _cols, const int _left, int _rigth) {
    size_t row, col;

    if (_left >= _rigth) return 0;

    if (_left < 0 && _rigth >= 0) _rigth += abs(_left);
    else if (_left < 0 && _rigth < 0) _rigth = abs(_left) - abs(_rigth);
    else if (_left >= 0 && _rigth > 0) _rigth -= _left;

    for (row = 0; row < _rows; row++)
        for (col = 0; col < _cols; col++)
            _matrix[row][col] = rand() % _rigth + _left;

    return 1;
}

void show_matrix(int ** _matrix, const size_t _rows, const size_t _cols) {
    size_t row, col;

    if (_cols && _rows)
        for (row = 0; row < _rows; row++, printf("\n"))
            for (col = 0; col < _cols; col++)
                printf("%5i", _matrix[row][col]);
    else printf("Нет данных для отображения!\n");
}

int is_positive_column(int ** _matrix, const size_t _rows, const size_t _col_index) {
    size_t row;

    for (row = 0; row < _rows; row++)
        if (_matrix[row][_col_index] < 0)
            return 0;
    return 1;
}

void resign(int ** _matrix, const size_t _rows, const size_t _col_index) {
    size_t row;

    for (row = 0; row < _rows; row++)
        _matrix[row][_col_index] *= -1;
}

void delete_matrix(int ** _matrix, size_t _rows) {
    size_t row;

    for (row = 0; row < _rows; row++)
        free(_matrix[row]);
    free(_matrix);
}

int ** create_matrix(int ** _matrix, const size_t _rows, const size_t _cols) {
    size_t row;
    _matrix = (int **)calloc(_rows, sizeof(int *));

    for (row = 0; row < _rows; row++)
        _matrix[row] = (int *)calloc(_cols, sizeof(int));

    return _matrix;
}