How to pass pointer to array of struct into function

Question

I tried making code to simulate boss fights. Firstly initialize the array of struct, making pointer out of it, and passing it into function.

#include <stdio.h>


struct machine_gun{
    char name[10];
    int rounds;
    int damage;
};

enum states{
    Tidak,
    Ya
};


void battle(struct machine_gun* wpn);

int main(){
    
    struct machine_gun weapon_list[2] = {
        {"Holger", 400, 20},
        {"M4LMG", 320, 25}
    };

    struct machine_gun *ptr = NULL;
    ptr = &weapon_list;
    int choice;
    
    printf("Boss has appeared! Enter 1 to fight the boss, 0 to run\n"); scanf("%d", &choice);
    if(choice == 1){
        battle(&ptr); 
    }
    else if(choice != 1){
        printf("You ran away.");
    }
}

void battle (struct machine_gun* wpn){
    int choice;
    int weapon_choice;
    int boss_hp = 1000;
    enum states state; 

    printf("###Weapon Lists###\n");
    for(int i = 0; i < 2; i++){
        printf("Name: %s\n", wpn[i]->name);
        printf(" Rounds: %d\n", wpn[i]->rounds);
        printf(" Damage: %d\n", wpn[i]->damage);
    }
    printf("\nBoss HP is 1000, are you sure you want to fight?\n1. Yes\n2. No\n"); scanf("%d", &choice);
    
    
    if(choice == 1){
        enum states state = Ya;
    }
    else{
        enum states state = Tidak;
    }
        switch(state){
            case Tidak:
            printf("Game Over!\nYou've been killed by the Boss.");
            case Ya:
            printf("Choose your weapon!\n");
            printf("1. %s with %d ammo and does %d damages\n", wpn[0]->name, wpn[0]->rounds, wpn[0]->damage);
            printf("2. %s with %d ammo and does %d damages\n", wpn[1]->name, wpn[1]->rounds, wpn[1]->damage);
            scanf("%d", &weapon_choice);
        }
    if(weapon_choice == 1){
        printf("You shot the boss with %d bullets\nCongratulation! You killed the boss, thanks for playing!\n", (1000/wpn[0]->damage));
        wpn[0]->rounds = wpn[0]->rounds - (1000/wpn[0]->damage); 
        printf("Your ammo remains: %d", wpn[0]->rounds);
    }
    else if(weapon_choice == 2){
        printf("You shot the boss with %d bullets\nCongratulation! You killed the boss, thanks for playing!\n", (1000/wpn[1]->damage));
        wpn[1]->rounds = wpn[1]->rounds - (1000/wpn[1]->damage); 
        printf("Your ammo remains: %d", wpn[1]->rounds);
    }
}

I tried to code like this, i know i messed up somewhere when making the pointers. Anyways, where did i do wrong? Is it because i didnt use typedef? Been trying to search the similar problem in stackoverflow but i just cant understand it properly

You have lots of wrong pointer type bugs. Start here: What compiler options are recommended for beginners learning C? Then compile again, go through all bugs the compiler points out and fix them one at a time. — Lundin
– Lundin, Commented Nov 24, 2022 at 12:51

Vlad from Moscow · Accepted Answer · 2022-11-24 13:07:11Z

In this assignment

ptr = &weapon_list;

the left operand has the type struct machine_gun * due to the declaration

struct machine_gun *ptr = NULL;

while the right operand has the type struct machine_gun ( * )[2] and there is no implicit conversion between the pointer types. The compiler should issue a message for this assignment statement.

Instead you need to write

ptr = weapon_list;

In this case the array designator is implicitly converted to pointer to its first element of the type struct machine_gun *.

Also as the function battle is declared like

void battle(struct machine_gun* wpn);

then you need to call it like

battle(ptr);

Otherwise the expression &ptr has incompatible pointer type struct machine_gun **

Also these calls of printf

    printf("Name: %s\n", wpn[i]->name);
    printf(" Rounds: %d\n", wpn[i]->rounds);
    printf(" Damage: %d\n", wpn[i]->damage);

as similar calls as for example

printf("Your ammo remains: %d", wpn[0]->rounds);

are incorrect.

Expressions like for example this wpn[i] has the type struct machine_gun.

So you need to write

    printf("Name: %s\n", wpn[i].name);
    printf(" Rounds: %d\n", wpn[i].rounds);
    printf(" Damage: %d\n", wpn[i].damage);

And change the similar way other calls of printf.

Else this declaration within the statement

if(choice == 1){
    enum states state = Ya;
}
else{
    enum states state = Tidak;
}

hide the declaration before the if statement.

enum states state;

So this switch statement

    switch(state){
        case Tidak:
        printf("Game Over!\nYou've been killed by the Boss.");
        case Ya:
        printf("Choose your weapon!\n");
        printf("1. %s with %d ammo and does %d damages\n", wpn[0]->name, wpn[0]->rounds, wpn[0]->damage);
        printf("2. %s with %d ammo and does %d damages\n", wpn[1]->name, wpn[1]->rounds, wpn[1]->damage);
        scanf("%d", &weapon_choice);
    }

uses the uninitialized variable state.

Also it seems you forgot to place the statement break in code snippets after each case label.

i thought when using pointer, i should use "->" instead of "." it seems i wrong, ty for the corrections btw

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