Structs

Pass Struct

Passing a struct by value gives a function its own copy of the fields.

by value The function receives a copy of the struct argument.
compute from fields The function can read fields from its copy to compute a result.

Pass Struct

width
pass_struct.c
Replay: real traced execution (multi-file project)
#include <stdio.h>

struct Box {
    int width;
    int height;
};

int area(struct Box box) {
    return box.width * box.height;
}

int main(void) {
    int width = 4;
    struct Box box = {width, 5};
    int result = area(box);

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

#include <stdio.h>

struct Box {
    int width;
    int height;
};

int area(struct Box box) {
    return box.width * box.height;
}

int main(void) {
    int width = 6;
    struct Box box = {width, 5};
    int result = area(box);

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

#include <stdio.h>

struct Box {
    int width;
    int height;
};

int area(struct Box box) {
    return box.width * box.height;
}

int main(void) {
    int width = 8;
    struct Box box = {width, 5};
    int result = area(box);

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

  1. width ← 4, box ← (empty)

    12int main(void) {13    int width→ 4 = 4; //@width=6, 814    struct Box box→ (empty) = {width4, 5};15    int result = area(box(empty));

  2. int area(struct Box box)

    8int area(struct Box box(empty)) {9    return box.width4 * box.height5;10}

  3. result ← 20

    14    struct Box box = {width, 5};15    int result→ 20 = area(box(empty));1617    printf("area=%d\n", result20);18    return 0;19}
    outputarea=20

  1. width ← 6, box ← (empty)

    12int main(void) {13    int width→ 6 = 6;14    struct Box box→ (empty) = {width6, 5};15    int result = area(box(empty));

  2. int area(struct Box box)

    8int area(struct Box box(empty)) {9    return box.width6 * box.height5;10}

  3. result ← 30

    14    struct Box box = {width, 5};15    int result→ 30 = area(box(empty));1617    printf("area=%d\n", result30);18    return 0;19}
    outputarea=30

  1. width ← 8, box ← (empty)

    12int main(void) {13    int width→ 8 = 8;14    struct Box box→ (empty) = {width8, 5};15    int result = area(box(empty));

  2. int area(struct Box box)

    8int area(struct Box box(empty)) {9    return box.width8 * box.height5;10}

  3. result ← 40

    14    struct Box box = {width, 5};15    int result→ 40 = area(box(empty));1617    printf("area=%d\n", result40);18    return 0;19}
    outputarea=40