如何修复代码中的分段错误以及将来修复此问题应遵循的过程是什么？

Question

I'm a beginner to C and came across a segmentation fault, which is what I understand as to be the program trying to access restricted or unavailable area of memory.

This issue is occurring for me in a function:

void process_command(struct pizzeria *the_pizzeria, char *command) {
    if (command[0] == 'n') {
        struct order **last_next_order_field = get_last_next_order_field(the_pizzeria);
        *last_next_order_field = create_order();
    }

    if (command[0] == 's') {
        //Line below receives error
        get_integer_input(the_pizzeria->selected_order, "");
    }

}

which is linked to this other function:

void get_integer_input(int *variable, char *prompt) {
    printf(prompt);
    scanf("%d", variable);
    getchar();
}

It must be noted that these functions are relating to this struct:

#define PIZZERIA_NAME_LENGTH 16
#define PIZZERIA_OWNER_LENGTH 16

struct pizzeria {
   char name[PIZZERIA_NAME_LENGTH];
   char owner[PIZZERIA_OWNER_LENGTH];
   int selected_order;
   struct order *orders;

}; 

I don't understand why when passing the_pizzeria->selected_order in get_interger_input in the function process_command makes pointer from integer without a cast as in my past functions of getting a char input instead I use the same process and don't receive an error.

I also set variable as a pointer so I don't understand the note produced by the terminal:

note: expected 'int *' but argument is of type 'int'

void get_integer_input(int *variable, char *prompt)

Answer 1

You don't show us these " past functions ", but I assume that they ask the user for name or owner. These elements of your struct are arrays, and if you pass their name as an argument it decays to a pointer to the first element.

In contrast, the integer is not an array. Therefore, you need to pass its address like this:

    if (command[0] == 's') {
        get_integer_input(&the_pizzeria->selected_order, "");
    }

If you are not very firm with operator precedence, better use parentheses:

    if (command[0] == 's') {
        get_integer_input(&(the_pizzeria->selected_order), "");
    }

The compiler is correct with its diagnostic message. You pass an integer, but the functions needs a pointer.