Heap Struct

A struct can also live in heap storage and be accessed through a pointer.

heap_struct.c

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

struct Box {
    int width;
    int height;
};

int main(void) {
    int width = ;
    struct Box *box = (struct Box *)malloc(sizeof(struct Box));

    if (box == 0) {
        return 1;
    }

    box->width = width;
    box->height = 4;
    int area = box->width * box->height;

    printf("area=%d\n", area);
    free(box);
    return 0;
}

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

struct Box {
    int width;
    int height;
};

int main(void) {
    int width = ;
    struct Box *box = (struct Box *)malloc(sizeof(struct Box));

    if (box == 0) {
        return 1;
    }

    box->width = width;
    box->height = 4;
    int area = box->width * box->height;

    printf("area=%d\n", area);
    free(box);
    return 0;
}

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

struct Box {
    int width;
    int height;
};

int main(void) {
    int width = ;
    struct Box *box = (struct Box *)malloc(sizeof(struct Box));

    if (box == 0) {
        return 1;
    }

    box->width = width;
    box->height = 4;
    int area = box->width * box->height;

    printf("area=%d\n", area);
    free(box);
    return 0;
}

heap struct `malloc(sizeof(struct Box))` requests storage for one `struct Box`.

arrow access The arrow operator reads or writes fields through the struct pointer.