es6.c

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

/* Clones the available portion of the first block into the second one */
int clone_block(char* m1, char* m2, const int size_m1, const int size_m2) {
    int size = size_m1 <= size_m2 ? size_m1 : size_m2;

    memcpy(m2, m1, size * sizeof(char));

    return memcmp(m1, m2, size);
}

/* Returns the power of a number. */
int powi(int n, int exp) {
    int tot = 1;

    for (int i = 0; i < exp; i++) {
        tot *= n;
    }

    return tot;
}

/* Returns the integer represented by the input string. */
int pos_atoi(char* str) {
    int tot = 0;

    int exp = strlen(str) - 1;

    for (int i = 0; str[i] != '\0'; i++) {
        int curr_char = str[i] - '0';
        
        if (curr_char < 0 || curr_char > 9) {
            return -1;
        }

        tot += powi(10, exp) * curr_char;

        exp--;
    }

    return tot;
}

int set_block(char* ptr, int size) {
    char input[size];

    if (fgets(input, size + 1, stdin) == NULL) {
        return -1;
    }

    memcpy(ptr, input, size * sizeof(char));

    return 0;
}

int main(int argc, char* argv[]) {
    // check if there are enough arguments
    if (argc < 3) {
        printf("Missing memory size.\n");
        exit(0);
    }

    // convert arguments into integers
    int size_m1 = pos_atoi(argv[1]);
    int size_m2 = pos_atoi(argv[2]);

    if (size_m1 == -1) {
        printf("Invalid M1 memory size argument.\n");
        exit(0);
    }

    if (size_m2 == -1) {
        printf("Invalid M2 memory size argument.\n");
        exit(0);
    }

    // allocate m1
    char* m1 = (char*) calloc(size_m1, sizeof(char));

    if (m1 == NULL) {
        printf("M1 not allocated.\n");
        exit(0);
    }

    printf("M1 allocated correctly, with size %d.\n", size_m1);

    // initialize m1
    int error_code = set_block(m1, size_m1);

    if (error_code == -1) {
        printf("Couldn't initialize M1.\n");

        free(m1);
        exit(0);
    }

    // allocate m2
    char* m2 = (char*) calloc(size_m2, sizeof(char));

    if (m2 == NULL) {
        printf("M2 not allocated.\n");

        free(m1);
        exit(0);
    }

    printf("M2 allocated correctly, with size %d.\n", size_m2);

    // clone (a portion of) m1 into m2
    if(clone_block(m1, m2, size_m1, size_m2)) {
        printf("M1 was not cloned into M2.\n");
    } else {
        printf("M1 was successfully cloned into M2.\n");

        printf("M1: %s\n", m1);
        printf("M2: %s\n", m2);
    }

    free(m1);
    free(m2);

    return 0;
}