Thread: I need help fixing a warning

Hi guys,

I'm a beginner in C and need help with my project for school. Here's my code,

Code:

/* -------------------------------------------------------
 * Carpooling
 * -------------------------------------------------------
 * This program will read a file that contains records of
 * people's addresses and will group the records together
 * based on the home zip code and work zip code.
*/

#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#define MAX_RECORDS 200

typedef struct
{
    char* last_name;
    char* first_name;
    char* address;
    char* city;
    char* state;
    int home_zip_code;
    int work_zip_code;
}address_record;

/* Extract the next field from the string passed by the caller.
 * The field is delimited by either a comma or the end of the
 * string */
char* next_field (char* pStart)
{
    char* pComma;
    int length;
    char* pField;

    pComma =  (char*) strchr(pStart, ',');
    if (pComma == NULL)
    {
        length = strlen(pStart);
    }
    else
    {
        length = pComma - pStart;
    }

    pField = (char*) calloc (1, length+1);
    assert (pField != NULL);
    
    strncpy(pField, pStart, length);
    return pField;
}

/* This function reads address records in the form of comma 
 * separated values from a file specified by the user and
 * sets up a dynamically allocated address record struct for
 * each record.  It puts pointers to the address record structs
 * into the array passed by the caller.
 * The caller specifies length of the array in nr_address.
 * This function sets nr_addresses to the number of array entries
 * actually filled.
*/
void get_input (address_record* addresses[], int* nr_addresses)
{
    int k;
    char file_name[1000];
    FILE* pAddressFile;
    address_record* pA;
    
    printf("Input file: ");
    scanf("%999[^\n]", file_name);
    
    pAddressFile = fopen(file_name, "r");
    
    if(pAddressFile == NULL)
    {
        fprintf(stderr, "Error trying to open %s to read file.\n", file_name);
        abort();
    }

    for(k = 0; k < MAX_RECORDS; k++)
    {
        addresses[k] = fscanf(pAddressFile, "%s,%s,%s,%s, %s,%d,%d\n",
                              pA->last_name, pA->first_name, pA->address,
                              pA->city, pA->state, &pA->home_zip_code,
                              &pA->work_zip_code);
    }
}

/* Sort an array of pointers to address records according to
 * home zip code and work zip code.
*/
void sort_by_zip_code (address_record* rec[], int length)
{

}
/* Output blocks of address records that have the same home
 * and work zip code.
*/
void output_matches(address_record* addresses[], int length)
{

}

int main()
{
    int nr_addresses = MAX_RECORDS;
    address_record* addresses[MAX_RECORDS];
    
    get_input(addresses, &nr_addresses);
    /*sort_by_zip_code(addresses, nr_addresses);
    output_matches(addresses, nr_addresses);*/
    return 0;
}

Now my problem is that I keep getting this error from the compiler,

warning: assignment makes pointer from integer without a cast

It appears to be coming from my for loop in my get_input function or atleast that's what the (Unix) compiler says. Could someone point me in the direction to fix this? Maybe a website or a hint on what I'm doing wrong would be great.

Any help is appreciated. Thanks!

-Nterpol

Edit: Would it be a better idea to get each of the item individually from the file? If so, do I need a loop to do it?

i look like u are declaring the array of pointers of type struct ... but u are not allocating any space. which will end up with the SEGFAULT.

Code:

address_record* addresses[MAX_RECORDS];

ssharish2005

Sweet!

Edit*

Now I'm confused on how I would go about getting the data. I would use fscanf (could I also use sscanf?) right? Do I store the results from fscanf in another variable that I declare or into the address array? Also, do I need a loop to get all the data from the file? I'm confused on this because when I compile and try to run, I get a Segmentation Fault.

Here's the part that I updated, everything else remained the same.

Code:

void get_input (address_record* addresses[], int* nr_addresses)
{
    int k;
    char file_name[1000];
    FILE* pAddressFile;
    address_record* pA;
    
    printf("Input file: ");
    scanf("%999[^\n]", file_name);
    
    pAddressFile = fopen(file_name, "r");
    
    if(pAddressFile == NULL)
    {
        fprintf(stderr, "Error trying to open %s to read file.\n", file_name);
        abort();
    }
    
    for(k = 0; k < MAX_RECORDS; k++)
    {
        addresses[k] = malloc(sizeof(address_record));
    }
}

So from here, I would use fgets inside (or outside?) of the loop to get each line from the file and from there use sscanf to get each of the parts of the line and store each of them in the struct members? Also, what do you mean by tokense and tokenising? I don't remember my teacher talking about this.

Edit*
One more question. My program has to be able to read 200 records. So would I need to multiply the sizeof in malloc by 200 or is it already taken care of by the address[k] assignment?

>addresses[k] = fscanf(pAddressFile, "%s,%s,%s,%s, %s,%d,%d\n",
> pA->last_name, pA->first_name, pA->address,
> pA->city, pA->state, &pA->home_zip_code,
> &pA->work_zip_code);

fscanf returns the number of conversions (an int), not the whole record.
Your updates to the record are via all those & references you pass as additional parameters.
And yes, you need to malloc each record as others have pointed out.

So something like this

Code:

void get_input (address_record* addresses[], int* nr_addresses)
{
    int k = 0;
    // snip filename stuff for brevity, it was reasonably OK

    while( k < MAX_RECORDS && !feof(pAddressFile) )
    {
        address_record temp;
        int result;
        result = fscanf(pAddressFile, "%s,%s,%s,%s, %s,%d,%d\n",
                              temp.last_name, temp.first_name, temp.address,
                              temp.city, temp.state, &temp.home_zip_code,
                              &temp.work_zip_code);
         if ( result == 7 ) {
             addresses[k] = malloc ( sizeof *addresses[k] );
             *addresses[k] = temp;
             k++;
         } else {
             // report bad format?  try and do some error recovery?
         }
    }
    *nr_addresses = k;
}

A better way of reading the file, which makes the error recovery so much simpler is

Code:

void get_input (address_record* addresses[], int* nr_addresses)
{
    char buff[BUFSIZ];
    int k = 0;
    // snip filename stuff for brevity, it was reasonably OK

    while( k < MAX_RECORDS && fgets(buff, sizeof buff, pAddressFile) )
    {
        address_record temp;
        int result;
        result = sscanf(buff, "%s,%s,%s,%s, %s,%d,%d\n",
                              temp.last_name, temp.first_name, temp.address,
                              temp.city, temp.state, &temp.home_zip_code,
                              &temp.work_zip_code);
         if ( result == 7 ) {
             addresses[k] = malloc ( sizeof *addresses[k] );
             *addresses[k] = temp;
             k++;
         } else {
             // report bad format?
         }
    }
    *nr_addresses = k;
}