Wednesday's Lecture

// Pointers are like wormholes...
// Where does a lecture on wormholes go?  In one ear, and out the other.
//
// At Aperture Laboratories, we have developed a specialised utility,
// a pointer gun.  It has two settings, `*` and `&`.
//
// 2017-08-23    Jashank Jeremy <{jashankj,z5017851}@cse.unsw.edu.au>

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

int main (int argc, char *argv[]) {
    int b = 1645;
    printf ("b = %d\n", b);
    int *pb;
    pb = &b;
    printf ("&b = %p\n", &b);
    printf ("pb = %p\n", pb);
    printf ("*pb = %d\n", *pb);

    *pb = 1647;
    printf ("*pb = %d\n", *pb);
    printf ("b = %d\n", b);

    int **ppb = &pb;
    **ppb = 1711;
    printf ("ppb = %p\n", ppb);
    printf ("*ppb = %p\n", *ppb);
    printf ("pb = %p\n", pb);
    printf ("**ppb = %d\n", **ppb);
    printf ("b = %d\n", b);

    return EXIT_SUCCESS;
}

// Show a character array.
// 2017-08-23   Jashank Jeremy <{jashankj,z5017851}@cse.unsw.edu.au>

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

void showCharArray (char *array);

int main (int argc, char *argv[]) {
    //char *str = {'A', 'N', 'D', 'R', 'E', 'W', '\0'};
    char *str = "ANDREW";
    printf ("%s\n", str);

    return EXIT_SUCCESS;
}

void showCharArray (char *array) {
    int index = 0;
    while (array[index] != '\0') {
        putchar (array[index]);
        index++;
    }
}

// Modifying a string literal is potentially lethal.
// 2017-08-23   Jashank Jeremy <{jashankj,z5017851}@cse.unsw.edu.au>

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

int main (int argc, char *argv[]) {
    /// If I declare the following:
    //
    // char *str = "It's currently 5:00 pm.";
    //
    /// ... and attempt to change a value in it:
    //
    // str[17] = '5';
    //
    /// ... our program will be shot down with the dreaded segmentation
    /// fault, a memory access error.  'dcc' shows "ASAN:DEADLYSIGNAL".

    char str[] = "It's currently 5:00 pm.";
    // char str[] = {'I', 't', '\'', 's', ..., '\0'};
    char *strA = str;

    printf ("str = %p\n", str);
    strA[17] = '5';
    printf ("%s\n", str);

    return EXIT_SUCCESS;
}