Thread: error subscripted value is neither an array nor pointer nor vector

Cause he either forgot and had non-compiling code or simply is a bad programmer talking out of his ..........

Originally Posted by cooper1200

too be fair there were lots of oh hang on no it works like this statements as he was explaining it but it did compile. anyway my code works now i need to impliment your other suggeston and have a function that gets the data from the user then assigns it in one lump.
coop

From the console scanf is the solution like in my above example, just use &tmp.VALUE for each expected value you put in the format parameter to use that right, for GUI I would suggest something like Tefaf's (I think that was the name) IUP Library

ok now whats up all i have done is switch the inputting of data to a separate function.

Code:

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

typedef struct Address
{
    int door_number;
    char *street;
    char *city;
    struct Address *next;
}Address;

void add_address(Address **first, Address **current);
Address get_address_details(void);
void print_list(Address *first);
void delete_list(Address **first);

int main()
{
    Address *first = NULL, *current = NULL;

    add_address(&first, &current);
    add_address(&first, &current);
    add_address(&first, &current);
    //add_address(first, current);
    //add_address(first, current);

    print_list(first);
    delete_list(&first);

    return 0;
}

void add_address(Address **first, Address **current)
{
    Address *p_new_element, temp;

    //get a new block of memmory and test the pointer isnt null
    p_new_element = malloc(sizeof(Address));
    if (!p_new_element)
    {
        printf("memmory allocation error");
        return;
    }

    temp = get_address_details();
    p_new_element = &temp;
    printf("door = %d street = %s city = %s\n", temp.door_number, temp.street, temp.city);
    printf("door = %d street = %s city = %s\n", p_new_element->door_number, p_new_element->street,
                                                                               p_new_element->city);
    if (*first == NULL) // no list yet so make p_new_element the head
    {
        *first = p_new_element;
        (*first)->next = NULL;
        *current = *first;
        return;
    }
    if ((*first)->next == NULL) //only one element in the list
    {
        (*first)->next = p_new_element;
        *current = p_new_element;
        (*current)->next = NULL;
        return;
    }
    //more than 2 elements
    (*current)->next = p_new_element;
    *current = p_new_element;
    (*current)->next = NULL;
}

Address get_address_details(void)
{
    char my_str[20];
    Address tmp;

    //get door number and assign it to the new elements member 'door_number'
    printf("Please enter the door number: ");
    scanf(" %d", &tmp.door_number);

    //get street name and assign it to my_str
    printf("Please enter street name: ");
    scanf(" %s", my_str);
    //create memory for the street name and assign the pointer address->street to point to it
    tmp.street = malloc(strlen(my_str) + 1);
    if (!tmp.street)
    {
        printf("error in getting memmory for street name");
        //return;
    }
    //copy contents of my_str into the memmory location pointed to by address->street
    strcpy(tmp.street, my_str);

    //get city name
    printf("Please enter city name: ");
    scanf(" %s", my_str);
    //create memory for the city name and assign the pointer address->city to point to it
    tmp.city = malloc(strlen(my_str) + 1);
    if (!tmp.city)
    {
        printf("error in getting memmory for city name");
        //return;
    }
    //copy contents of my_str into the memmory location pointed to by address->city
    strcpy(tmp.city, my_str);

    return tmp;
}

void print_list(Address *first)
{
    int count = 1;
    Address *temp = first;

    while (temp)
    {
        printf("address no %d is door number %d street %s city %s\n", count, temp->door_number,
                                                                       temp->street, temp->city);
        count++;
        temp = temp->next;
    }
}

void delete_list(Address **first)
{
    int count = 1;
    Address *temp = NULL;

    printf("freeing memmory....\n");
    while (*first)
    {
        temp = (*first)->next; // set temp to point at the next element in the list
        printf("freeing element %d's street name\n", count);
        free((*first)->street); //free the memmory block that holds firsts street name
        printf("freeing element %d's city name\n", count);
        free((*first)->city); //free the memmory block that holds firsts city name
        printf("freeing struct %d's memmory\n", count);
        free(*first); //free the memmory block that holds the first element
        (*first) = temp; // set first to point at the next memmory block;
        count++;
    }
    printf("finished freeing all allocated memmory\n");
}

it compiles and the two printf statements after assigning temp to the pointer display the info correctly as entered. but once i hit the print function it never breaks out and prints a lot of rubbish to the screen
coop

For starters set temp to 0 like this:

Code:

 Address temp = {0};

when initialising l, second NEVER give a pointer to a stack variable to a pointer value being returned, at work so few opportunities to respond, and have short replies, I'll take another look when I get a chance

Sorry meant tmp in get_address_details(), still don't have time to do thorough check of your code however look at when you fill the "next" parameter and make sure the it's the previous address that recieves the pointer and don't tamper with the tmp one

ok god knows how this is happening and what the hell has caused it but it appears that when setting the head of the list the first->next doesn't get set to null; therefor the second if doesnt get run. and all other nodes are set on current so nothing is linked and there is no null to terminate the print loop.

You got a memory leak in add_address()

Here's an example of handing those pointers information

Code:

*p_new_address = get_address_details();
if ( p_prv_address) p_prv_address->next = p_new_address;

Also you should allocate all memory you're going to use BEFORE asking the user for their details

ok im not getting this.... i have done nothing other than move the data entry into another function and yet it suddenly changes how the program operates ie it doesn't work. the only call to malloc in add_address gets the lump of memory for the new node. i would of thought i need that until i call delete list and if i try to free it at the end of the function i get double free or corruption (out)
Aborted (core dumped)

Process returned 134 (0x86) execution time : 7.599 s
Press ENTER to continue.

i just don't understand how something that appears to work as far as the printf's in get address show suddenly stops a previously working section of code working.

coop

ok thanks for that it all works now.

Originally Posted by awsdert

Also you should allocate all memory you're going to use BEFORE asking the user for their details

i dont know what the user is going to input it might be the full 20 characters or might just be 5 should i malloc for the full 20 then use realloc to reduce it to the size required?

Yep, from a user standpoint we don't want to give our details only to find an error message saying not enough memory, we just wasted our time as a result, better to give a smoother experience by saying not enough memory from the get go and skipping the message if we got the memory and just continuing normally