Unclear behavior of structs in a function - arrays

Question

I am creating a project and I encountered behavior that is not supposed to happen (at least as far as I know). I am trying to change values in a struct array inside of a function addOrder. in main() I give struct's address to a function addOrder (and this is the first warning). Then I try to change its contents in the named function. I should only be able to change using ->, however, I get errors this way and I can only change using data[0].someName
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#define MENU_TITLE "----Welcome to order manager!---" // menu title
#define MENU_SIZE 4 //change based on menu options
#define INPUT_MSG "Please choose one of the following options" //enter input message (range is added later automatically)
#define SIZE 25 //size of option message array
#define STREET_NAME_SIZE 50 //size of street name array
#define BUILDING_NUMBER_SIZE 10 //size of building number array
#define EMAIL_SIZE 40 //size of email array
#define INPUT_PHONE_MAX 12
typedef struct Data{
char streetName[STREET_NAME_SIZE];
char buildingNumber[BUILDING_NUMBER_SIZE];
unsigned long long phoneNumber;
char email[EMAIL_SIZE];
}Data;
void loadOrderAmount(int *orderAmount);
void showMenu(char *menuTitle, int menuSize, char *inputMsg);
int getChoise();
void addOrder(Data *data, int *orderAmount);
void getEmail(char *email);
unsigned long long getPhoneNumber();
int main(){
int orderAmount = 0;
loadOrderAmount(&orderAmount);
Data data[orderAmount + 1];
int choise = 0;
showMenu(MENU_TITLE, MENU_SIZE, INPUT_MSG);
while(!choise){
choise = getChoise();
}
printf("\n");
switch(choise){
case 1:
addOrder(&data,&orderAmount); // This gives first warning
break;
case 2:
//removeOrder(data);
break;
case 3:
//editOrder(data);
break;
case 4:
printf("Have a nice day\n");
return 0;
}
printf("in main data %d\n",&data);
//printf("%s %s ",data[0].streetName,data[0].buildingNumber);
//printf("+%llu ",data[0].phoneNumber);
printf("in main %s %llu\n",data[0].email,data[0].phoneNumber);
return 0;
}
void addOrder(Data *data,int *orderAmount){
int amount = *orderAmount; //it is equal to 0
char email[41];
char street[51];
char buildingNumber[11];
printf("Adding an order...\n\n");
//++orderAmount;
// getStreetName(data, &orderAmount);
// getBuildingNumber(data,&orderAmount);
data[amount]->phoneNumber = getPhoneNumber(); //why this does not work?
getEmail(email);
strcpy(data[0].email,email); // why this works? its a function....
printf("In function data %d\n", data);
printf("in struct %s %llu\n",data[0].email, data[0].phoneNumber);
}
}
This is only a part of a code that is relevant and most functions are missing. Can anyone help me with this?

Answer 1

The function addOrder is declared like
void addOrder(Data *data, int *orderAmount);
But you are calling it passing the first argument of the type Data ( * )[orderAmount + 1]
addOrder(&data,&orderAmount);
You need to call it like
addOrder( data, &orderAmount );
Instead of this statement
data[amount]->phoneNumber = getPhoneNumber();
you have to write
data[amount].phoneNumber = getPhoneNumber();
And instead of this call
printf("In function data %d\n", data);
you have to write
printf("In function data %p\n", ( void * )data);
Pay attention to that within the function the expressions
data[amount]
and
data[0]
are not the same because amount is not equal to zero. The function is called with the argument orderAmount (passed by reference) that is assigned to amount.

Answer 2

This is how you solve this error:
Compiler points at the line addOrder(&data,&orderAmount); saying something strange "error passing argument 1 blablabla". We don't actually need to understand more than "error argument 1".
Could it be that the compiler is right and something is wrong with argument 1?
Hmm which one is argument 1, it must be &data.
Check the declaration of data, it is Data data[orderAmount + 1];. It's an array!
What did they teach us in beginner class? Ah, arrays decay to a pointer to the first element when passed to a function. So there is no need for &.
Change the call to addOrder(data,&orderAmount);
Compile again.