[loonyt7]

I have this program that I have written in C that when I compile and run the program it run thru asking for the data to be entered then when I am done entering the information in it displays on the screen. When I hit any key to exit I get an error.

Can some one help me on figuring out what is causing my program not to exit correctly.

Code:

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

struct guest {
       int age;
       char lastname[30];
};

struct guest* guestlist_allocate(int number);
void guestlist_deallocate(struct guest* p, int number);
void guestlist_readall(struct guest* p, int number);
void guestlist_display(struct guest* p, int number);

int main()
{
    int n = 3;
    struct guest* guestlist;

    printf("How many guests do you need to enter? ");
    scanf("%d", &n);

    guestlist_allocate;

    while(n <= 0)
    {
         printf("Error you entered a negative number!");
         break;
    }

    printf("Reading data for %d guests\
", n);
    guestlist_readall(guestlist, n);

    printf("Displaying data for %d guests\
", n);
    guestlist_display(guestlist, n);

    guestlist_deallocate;

    system("PAUSE");
    return 0;
}

struct guest* guestlist_allocate(int number)
{
       char lastname;
       int age = 0;
       int n;
       char buffer[30];

       struct guest *guestlist;
       guestlist = malloc (sizeof(struct guest) * n); 
       strcpy(lastname,buffer);

}

void guestlist_deallocate(struct guest* p, int number)
{
     int i;
     int n;
     struct guest *guestlist;

     for (i = 0; i < n; i++)
         free(p[i].lastname);
     free(guestlist);
}

void guestlist_readall(struct guest* p, int number)
{
     char lastname;
     int age=0;
     int i;

     for( i = 0; i < number; i++)
     {
          printf("\Guest #%d:\
 ", i);
          printf("\\Enter lastname: ");
          scanf("%29s", p[i].lastname);
          printf("\\Enter age: ");
          scanf("%ld", &p[i].age);
     }
}

void guestlist_display(struct guest* p, int number)
{
     int i;
     for(i = 0; i < number; i++)
           printf("\Guest #%d: lastname = %s\age = %ld\
", i, p[i].lastname, p[i].age);
}

 

[error10]

You need to actually call guestlist_allocate() with the number of records you want.

 

[loonyt7]

Now when I do as you stated above and call the function as soon as I enter how many guest the program errors.

 

[error10]

Well, what you need to do is read the errors.

 

[Spotswood]

This should help you a little:

Code:

struct guest* guestlist_allocate(int number)
{
       char lastname;
       int age = 0;
       [B]//int n;[/B]
       char buffer[30];

       struct guest *guestlist;
       guestlist = (guest*)malloc (sizeof(struct guest) * [B]number[/B]); 
[B]       // Heh???
       //strcpy(lastname,buffer);[/B]
       return guestlist;
}

 

[loonyt7]

The reason I had the strcpy in the code is because I have to set the lastname field of each element to an empty string.

I made the suggested changes but still have the same result.

If I had errors to read I wouldn't be having as many issues. I do not get errors upon compilation the problem comes in when I am exiting out of the program after entering the information.

Below is what my code looks like now.

Code:

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

struct guest {
       int age;
       char lastname[30];
};

struct guest* guestlist_allocate(int number);
void guestlist_deallocate(struct guest* p, int number);
void guestlist_readall(struct guest* p, int number);
void guestlist_display(struct guest* p, int number);

int main()
{
    int n = 0;
    struct guest* guestlist;

    printf("How many guests do you need to enter? ");
    scanf("%d", &n);

    guestlist_allocate(n);

    while(n <= 0)
    {
         printf("Error you entered a negative number!");
         break;
    }

    printf("Reading data for %d guests\
", n);
    guestlist_readall(guestlist, n);

    printf("Displaying data for %d guests\
", n);
    guestlist_display(guestlist, n);

    guestlist_deallocate(guestlist, n);

    system("PAUSE");
    return 0;
}

struct guest* guestlist_allocate(int number)
{
       char lastname;
       int age = 0;
       char buffer[30];

       struct guest *guestlist;
       guestlist = malloc (sizeof(struct guest) * number); 
       return guestlist;
}

void guestlist_deallocate(struct guest* p, int number)
{
     int i;
     int n;
     struct guest *guestlist;

     for (i = 0; i < n; i++)
         free(p[i].lastname);
     free(guestlist);
}

void guestlist_readall(struct guest* p, int number)
{
     char lastname;
     int age=0;
     int i;

     for( i = 0; i < number; i++)
     {
          printf("\Guest #%d:\
 ", i);
          printf("\\Enter lastname: ");
          scanf("%29s", p[i].lastname);
          printf("\\Enter age: ");
          scanf("%ld", &p[i].age);
     }
}

void guestlist_display(struct guest* p, int number)
{
     int i;
     for(i = 0; i < number; i++)
           printf("\Guest #%d: lastname = %s\age = %ld\
", i, p[i].lastname, p[i].age);
}

 

[Spotswood]

You never set guestlist to the value returned from guestlist_allocate(). And guestlist_deallocate()'s loop is testing 'n' rather than 'number'. And either remove the call to free the lastname or make lastname a pointer and allocate its memory.

 

[error10]

And remember to run the program in the debugger.

 

[loonyt7]

Okay I made some changes as was suggested and then continued on with making changes and I have narrowed my issues down to the following section of my code. When I run the program through the debugger I get an error "an access violation (segmentation fault) raised in your program". I need to use something similar to what I have done but apparently I have something not right in the code. Any help would be apprecaited.

Code:

void guestlist_readall(struct guest* p, int number)
{
    char lastname;
    int age=0;
    int i;
    char buffer[30];
    int name_length;

    for( i = 0; i < number; i++)
    {
          printf("\Guest #%d:\
 ", i);
          printf("\\Enter lastname: ");
          scanf("%29s", buffer);
          name_length = strlen(buffer);
          guest* p[i].lastname = malloc(sizeof(char)* (name_length+1));
          strcpy(guest* p[i].lastname, buffer);

          printf("\\Enter age: ");
          scanf("%ld", &p[i].age);
    }
}

 

[loonyt7]

Below is my most current version of the program I am working on. Now when I run this through the debugger it is not giving me anything but after the program runs through it errors. Almost like I am back at square one again. I have written this code from scratch so any help getting the problems fixed would be a great help.

Code:

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

struct guest {
       int age;
       char lastname[30];
};

struct guest* guestlist_allocate(int number);
void guestlist_deallocate(struct guest* p, int number);
void guestlist_readall(struct guest* p, int number);
void guestlist_display(struct guest* p, int number);

int main()
{
    int n = 0;
    struct guest* guestlist;
    int number;
    struct guest* p;

    printf("How many guests do you need to enter? ");
    scanf("%d", &n);

    guestlist_allocate(guestlist);

    while(n <= 0)
    {
         printf("Error you entered an invalid number!");
         break;
    }

    printf("Reading data for %d guests\
", n);
    guestlist_readall(guestlist, n);

    printf("Displaying data for %d guests\
", n);
    guestlist_display(guestlist, n);

    guestlist_deallocate(guestlist, p);

    system("PAUSE");
    return 0;
}

struct guest* guestlist_allocate(int number)
{
    char lastname;
    int age = 0;
    char buffer[30];

    struct guest *guestlist;
    guestlist = malloc (sizeof(struct guest) * number); 
    return guestlist;
}

void guestlist_deallocate(struct guest* p, int number)
{
    int i;
    struct guest *guestlist;

    for (i = 0; i < number; i++)
         free(p[i].lastname);
         free(guestlist);
}

void guestlist_readall(struct guest* p, int number)
{
    char lastname;
    int age=0;
    int i;
    char buffer[30];
    int name_length;

    for( i = 0; i < number; i++)
    {
          printf("\Guest #%d:\
 ", i);
          printf("\\Enter lastname: ");
          scanf("%29s", buffer);
          name_length = strlen(buffer);
          strcpy(p[i].lastname, buffer);

          printf("\\Enter age: ");
          scanf("%ld", &p[i].age);
    }
}

void guestlist_display(struct guest* p, int number)
{
    int i;
    for(i = 0; i < number; i++)
           printf("\Guest #%d: lastname = %s\age = %ld\
", i, p[i].lastname, p[i].age);
}

 

[error10]

What compiler and what OS are you using? The program should have crashed much earlier than at exit.

Compiling this with gcc shows exactly where and what the problems are:

Code:

test.c: In function 'main':
test.c:25: warning: passing argument 1 of 'guestlist_allocate' makes integer from pointer without a cast
test.c:10: note: expected 'int' but argument is of type 'struct guest *'
test.c:39: warning: passing argument 2 of 'guestlist_deallocate' makes integer from pointer without a cast
test.c:11: note: expected 'int' but argument is of type 'struct guest *'

Looks like you have *'s where they don't belong, or missing them when you need them. It's very common, and trips up even experienced C programmers.

 

[Spotswood]

This doesn't crash:

Code:

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

struct guest {
    int age;
    char lastname[30];
};

struct guest* guestlist_allocate(int number);
void guestlist_deallocate(struct guest* p, int number);
void guestlist_readall(struct guest* p, int number);
void guestlist_display(struct guest* p, int number);

int main()
{
    int n = 0;
    struct guest* guestlist;
    int number;
    struct guest* p;

    printf("How many guests do you need to enter? ");
    scanf("%d", &n);

    [B]guestlist = guestlist_allocate(n);
[/B]
    while(n <= 0)
    {
        printf("Error you entered an invalid number!");
        break;
    }

    printf("Reading data for %d guests\
", n);
    guestlist_readall(guestlist, n);

    printf("Displaying data for %d guests\
", n);
    guestlist_display(guestlist, n);

    guestlist_deallocate(guestlist, n);

    system("PAUSE");    
    return 0;
}

struct guest* guestlist_allocate(int number)
{
    char lastname;
    int age = 0;
    char buffer[30];

    struct guest *guestlist;
    guestlist = (guest *)malloc (sizeof(struct guest) * number); 
    return guestlist;
}

void guestlist_deallocate(struct guest* p, int number)
{
    int i;
    struct guest *guestlist;

    for (i = 0; i < number; i++)
[B]        //free(p[i].lastname)
        ;

    free(p);[/B]
}

void guestlist_readall(struct guest* p, int number)
{
    char lastname;
    int age=0;
    int i;
    char buffer[30];
    int name_length;

    for( i = 0; i < number; i++)
    {
        printf("\Guest #%d:\
 ", i);
        printf("\\Enter lastname: ");
        scanf("%29s", buffer);
        name_length = strlen(buffer);
        strcpy(p[i].lastname, buffer);

        printf("\\Enter age: ");
        scanf("%ld", &p[i].age);
    }
}

void guestlist_display(struct guest* p, int number)
{
    int i;
    for(i = 0; i < number; i++)
        printf("\Guest #%d: lastname = %s\age = %ld\
", i, p[i].lastname, p[i].age);
}

 

[loonyt7]

Thanks for the help on this. The changes you made do make sense to me and I understand them.

 

[loonyt7]

I am wondering if anyone could help me change this program for another assignment that I have. I need to take the above program and change it according to the following instructions. I need some direction on how to go about doing this. I am not wanting some one to just give me the answer.

 struct guest* guest_create( char* lastname, int age, );
o allocates a new struct guest data structure which address you will return
o Set the lastname field to a newly allocated copy of the string pointed to by
the lastname parameter
o Set the age field to the value in the age parameter
o Set the next pointer to NULL
 void guestlist_deallocate (struct guest* p);
o Deallocates all the elements of the struct guest linked list pointed to by p
 struct guest * guestlist_readall (int number);
o This function will read the name and age of number guests from the user
o For each guest, create a new struct guest data structure, assign appropriate
value to its fields (the age value and a copy of the lastname typed by the
user), and link it to the end of a linked list of all struct guest read so far.
o You will return a pointer to the first struct guest of the linked list
o Use the guest_create function to help you write this one
 void guestlist_display(struct guest* p);
o Display information about each guest (name and age) on the screen

 

[loonyt7]

Below is what I have come up with but can not get to compile. Any help on pointing me in the right direction would be a great help

Code:

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

struct guest{
       int age;
       char lastname;
       struct node *next;
};

struct guest* guest_create(char* lastname, int age);
void guestlist_deallocate(struct guest* p);
struct guest * guestlist_readall(int number);
void guestlist_display(struct guest* p);

int main()
{
    int n = 0;
    struct guest* guestlist;
    int number;
    struct guest* p;

    printf("How many guests do you need to enter? ");
    scanf("%d", &n);

    struct guest *guest_create = NULL;

    while(n <= 0)
    {
         printf("Error you entered a negative number!");
         break;
    }

    printf("Reading data for %d guests\
", n);
    guestlist_readall(number);

    printf("Displaying data for %d guests\
", n);
    guestlist_display(p);

    guestlist_deallocate(p);

    system("PAUSE");
    return 0;
}

struct guest* guest_create(char* lastname, int age)
{
    struct guest *tmp;

    if(lastname == NULL)
    {
         lastname = (struct guest*)malloc(sizeof(struct guest));
         if(lastname == NULL)
         {
              printf("Error! memory is not available\
");
              exit(0);
         }
         lastname-> age = age;
         lastname-> next = lastname;
    }
    else
    {
        tmp = lastname;

        while (tmp-> next != lastname)
            tmp = tmp -> next;
        tmp -> next = (struct guest *)malloc(sizeof(struct guest));
        if(tmp -> next == NULL)
        {
               printf("Error! memory is not available\
");
               exit(0);
        }
        tmp = tmp->next;
        tmp -> age = age;
        tmp -> next = lastname;
    }
    return lastname;
}

void guestlist_deallocate(struct guest* p)
{
    struct guest *current, *tmp;

    current = lastname->next;
    lastname->next = NULL;
    while(current != NULL)
    {
         tmp = current -> next;
         free(current);
         current = tmp;
    }
}

struct guest * guestlist_readall(int number)
{
    struct guest {
    int age;
    struct node *next;
};

    char lastname;
    int age=0;
    int i;
    char buffer[30];
    int name_length;

    for( i = 0; i < number; i++)
    {
          printf("\Guest #%d:\
 ", i);
          printf("\\Enter lastname: ");
          scanf("%29s", buffer);
          name_length = strlen(buffer);
          strcpy(lastname, buffer);

          printf("\\Enter age: ");
          scanf("%ld", &age);
    }
}

void guestlist_display(struct guest* p)
{
    struct guest *current
    current = lastname;

    if(current != NULL)
    {
         do
         {
               printf("%d\",current->age);
               current = current->lastname;
         }while(current != lastname);
         printf("\
");
    }
    else
         printf("The list is empty\
");

}

 

[Pooping^fish]

Code:

while(n <= 0)
    {
        printf("Error you entered an invalid number!");
        break;
    }

Lol'ing that no one has caught this yet.

 

[error10]

I caught it: zero certainly isn't a negative number. But it seemed irrelevant to the problem.

 

[Spotswood]

Too many errors to fix for you.

What is a node?

Code:

struct guest{
       int age;
       char lastname;
       struct node *next;
};

Hmmmm, what do you think is wrong with this line?

Code:

lastname = (struct guest*)malloc(sizeof(struct guest));

I suggest you recompile your code after every change or additional line of code. Writing large chunks of code without intermediate compiles only leads to this kind of mess.