Assignment from incompatible pointer type

**brehon1104** · 03-03-2011

The problem has something to do with my temp in the sort function. It says assignment from incompatible pointer type when i set "temp" = to something. It's a bubble sort. suggestions?

thank you,

brehon1104

Code:


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


//function protos
void addentry();
void delentry ();	
void printentry ();
void sort ();
void random ();
void clear ();
void search ();

// struct for an entry
typedef struct
{
       char *fname;
       char *lname;
       char *num;
} acontact;

acontact *ac; //pointer toward struct named "ac"
char first[100];
char last[100];
int counter = 0; // keeps tract of contacts
int i = 0; //printing index

// set eeverything to 0


main() 
{


int choice = 0;

      while (choice !=8)
{
      printf("\n\nYellow Pages Editor v 1.06");
      printf("\n1) Add entry");
      printf("\n2) Delete entry");
      printf("\n3) Display Yellow Pages");
      printf("\n4) Sort entries");
      printf("\n5) Find a number");
      printf("\n6) Randomly select a friend");
      printf("\n7) Erase phonebook");
      printf("\n8) Exit");
      printf("\n\nWhat do you want to do? ");
      scanf("%d", &choice);
      
      
      
      switch (choice) {
      //add entry
             case 1:
                  addentry();
                  system("\npause\n\n");
                  break;
                   
     //delete entry
             case 2:
                  delentry();
                  system("\npause\n\n");
                  break;
      //display
             case 3:
                  printentry();
                  system("\npause\n\n");
                  break;
      
      //sort
            case 4:
                 sort();
                 system("\npause\n\n");
                 break;
                 
      //find a name given a number
             case 5:
                  search();
                  system("\npause\n\n");
                  break;
                  
      //randomly select a friend
             case 6:
                  random ();
                  system("\npause\n\n");
                  break;
                  
      // erase phonebook entirely
             case 7:
                  clear ();
                  system("\npause\n\n");
                  break;
                 
                  default:
                         printf("Try Again.");
                         break;
             
             

} //end switch
} // end while
} // end main


void addentry ()
{
	if(counter == 0)
	{
        ac = (acontact *) malloc (sizeof(acontact) + (counter*20));
    }
    else
    {
        ac = (acontact *) realloc (ac, sizeof(acontact) + (counter*20) + 20);
    }
    if(ac == NULL)
    {
        printf("out of memory\n");
    }
    else
    {
    ac[counter].fname = (char *) malloc (sizeof(char)*15);
    ac[counter].lname = (char *) malloc (sizeof(char)*15);
    ac[counter].num = (char *) malloc (sizeof(char)*20);
    printf("\nFirst name: ");
    scanf("%s", ac[counter].fname);
    printf("Last name: ");
    scanf("%s", ac[counter].lname);
    printf("Phone number (no dash): ");
    scanf("%s", ac[counter].num);
    
    counter++;
    printf("Entry added to Yellow Pages!\n\n");
    }
}	//end add

void delentry ()
{
    int i;
    int removed = 0;
    
    printf("\nFirst name: ");
	scanf("%s", first);
    printf("Last name: ");
	scanf("%s", last);
	
	// string comparison
	for (i = 0; i<counter; i++)
	{
        if ((ac[i].fname == NULL) && (ac[i].lname == NULL)) continue;
		if ((stricmp(ac[i].fname, first) == 0) && (stricmp(ac[i].lname, last) == 0))
		{
			ac[i].fname = NULL;
			ac[i].lname = NULL;
			ac[i].num = NULL;
			removed = 1;	
			break;
		}
		if(removed == 1)
		{
                   printf("\nUser Deleted!\n\n");
        }
        else
        {
                   printf("\nUser not found!\n\n");
        }
    }
}// end del funct

void printentry ()
{
     if (counter==0)
     printf("Nothing to display.\n\n");
     else
     {
	int i;
		printf("\n\nYellow Page Entries:\n\n");
		for(i=0; i<counter; i++)
		{
			if (ac[i].lname != NULL)
			{
				printf("%s %s %s\n", ac[i].fname, ac[i].lname, ac[i].num);
			}// end if
		} //end for
}// end else
} //end print


void sort ()
{
     int i;
     int j;
     acontact *temp; // the problem is here
     temp = (char *) malloc (sizeof(char)*15); // and here
     

     int choice;
     printf("Sort by:\n");
     printf("1) First name\n");
     printf("2) Last name\n");
     printf("Which? ");
     scanf("%d", choice);
     
     switch (choice) {
            case 1:
                 
        if (counter == 0)
        printf("No entries to sort.");
        
        else {
        for (i = 0; i<counter; i++)
{
        for (j = 0; j<counter; j++)
        {
            if ((stricmp(ac[j].fname, ac[i].fname)) > 0)
            {
                temp = ac[j].fname;
                ac[j].fname = ac[i].fname;
                ac[i].fname = temp;
                
            }// end if
        }// end inner for
}// end outer for
printf("Sorted");
}// else else

         system("\npause\n\n");
         break;

// if this doesnt work instead of j+1 make it i 
case 2:
                 if (counter == 0)
        printf("No entries to sort");
        
        else {
        for (i = 0; i< counter-1; i++)
{
        for (j = 0; j < counter-1; j++)
        {
            if ((stricmp(ac[i].lname, ac[j].lname)) > 0)
            {                     
                temp = ac[j].lname;
                ac[j].lname = ac[i].lname;
                ac[i].lname = temp;
                
            }// end if
        }// end inner for
}// end outer for
}// else else

            system("\npause\n\n");
            break;
           
}// end switch
}// end sort funct


void random ()
{
     int y;
     if (counter == 0)
     printf("No entries!");
     
     else
     {
     y = rand()%counter;
     printf("%s %s %s", ac[y].fname, ac[y].lname, ac[y].num);
     }
}
     

void search ()
{
     if (counter == 0)
     printf("\nNo entries.\n\n");
     
     else {
     int g = 0;
     char ifname[100];
     char ilname[100];
     printf("Enter the first name: ");
     scanf("%s", ifname);
     printf("Enter the last name: ");
     scanf("%s", ilname);
     
     for(g=0;g<counter;g++)
     {
          if ((stricmp(ac[i].fname, ifname) == 0 && (stricmp(ac[i].lname, ilname)) == 0))
          printf("\n%s\n\n", ac[i].num);
     }// end for
} // end else
} // end search func
     
 
void clear ()
{
     if (counter ==0) 
     printf("\nNothing to erase\n");
     
     else{
          
          counter == 0;
          free(ac);


}// end else
}// end clear

**nonoob** · 03-03-2011

temp and fname are char arrays of 15 characters. So to move such data you will need:

Code:

memcpy(temp, ac[j].lname, 15);
memcpy(ac[j].lname, ac[i].lname, 15);
memcpy(ac[i].lname, temp, 15);

Also, your delentry() function has poroblems. You shouldn't just assign NULL to the pointers. You should use free() to deallocate the memory that you allocated earlier. Then you can assign NULL if you wish.

**brehon1104** · 03-03-2011

i posted your solution in the sort function. It still says the same thing, and still crashes when you enter the switch statement within the sort function.

**Phenax** · 03-03-2011

Originally Posted by brehon1104

i posted your solution in the sort function. It still says the same thing, and still crashes when you enter the switch statement within the sort function.

In addition to what others have pointed out, you have other problems in your code.
Line 204

Code:

scanf("%d", choice);

Line 304

Code:

counter == 0;

Seems like you forgot to free temp in your sort function.
Also, you should make your main function return an integer is that is standard behavior these days.
Maybe I'm missing something, but on Line 197 why are you casting your malloc to (char *)? I don't see the point, and it throws a warning on my compiler.

**hk_mp5kpdw** · 03-03-2011

Code:

ac[counter].fname = (char *) malloc (sizeof(char)*15);
ac[counter].lname = (char *) malloc (sizeof(char)*15);
ac[counter].num = (char *) malloc (sizeof(char)*20);

1. Avoid casting the return value from the malloc call, the returned void* can be safely assigned to other pointer types (in your case a char*) without the need of a cast.
2. sizeof(char) is guaranteed to be 1 and since anything multiplied by 1 is just simply that original value it is unneeded here.

Code:

ac[counter].fname = malloc (15);
ac[counter].lname = malloc (15);
ac[counter].num = malloc (20);

It says assignment from incompatible pointer type when i set "temp" = to something.

Code:

acontact *temp; // the problem is here
temp = (char *) malloc (sizeof(char)*15); // and here

3. Your cast (which I already mentioned you should not be using) is converting the malloc'd memory into a char* which does not match the acontact* you are attempting to assign it to.
4. You are mallocing an incorrect size, you are asking for 15 bytes when you should be asking for whatever sizeof(acontact) is.
5. Why even use dynamic memory allocation here at all? Just have a temp acontact object instead of a pointer to one.

In general:
6. You have no error checking code for your dynamic memory allocations. You simply assume it all works.
7. Your data entry (the scanf calls do not limit how many characters they accept into your buffers. A user can type in 50 characters for a first name for example and the scanf will happily try to store it into a buffer that is only 15 characters in size.

**~~CommonTater~~** · 03-03-2011

Ok... look at this rationally... you have an array of structs but in your sort you are moving only partial contents of the struct... This is going to cause data corrpution...

John Smith ... Fred Doe ... Cathy Martin ...
would become
Cathy Smith ... Fred Doe ... John Martin...

You have to move the entire struct, not just the part you are sorting on.

Code:

// struct for an entry
typedef struct tContact
{
       char fname[20];
       char lname[20];
       char num;
} Contact, *pContact;

// array of pointers to contacts
pContact Contacts = Null;

// how many contacts.
int LastContact = 0;  
int MaxContacts = 0;

// add new contacts to array
int AddNewContact( char* nfirst, char *nlast)
  { ++LastContact;
     // expand array by 10s 
     if (LastContact > MaxContacts)
       { MaxContacts += 10;
         Contacts = realloc(Contacts, sizeof(tContact) * MaxContacts); }
    // add new contact
    strncpy( Contacts[LastContact]->fname,  nfirst, 20 );  
    strncpy(  Contacts[Lastcontact]->lname, nlast, 20); 
    return LastContact; } 

// delete, edit, etc goes here



// now when you come to your sort
// all you have to do is swap pointers.
void sort ()
{
     int i;
     int j;
     pcontact temp;    
     
      for (i = 0; i < LastContact; i++)
        for (j = 0; j < LastContact; j++)
           if ((stricmp(Contacts[j]->fname, Contacts[i]->fname)) > 0)
            {   temp = Contacts[j];
                Contacts[j] = Contacts[i];
                Contacts[i] = temp; }
       printf("Sorted"); }

I'm sure there's a couple of minor errors in there somplace --this is untested code -- but I trust you get the concepts involved....

**brehon1104** · 03-09-2011

Thank you everyone, I got it figured out!

Thread: Assignment from incompatible pointer type

Thread Tools

Search Thread

Display

Assignment from incompatible pointer type

Similar Threads

passing argument from incompatible pointer type

incompatible pointer type?

pointers, structures, and malloc

Please Help - Problem with Compilers

Could somebody please help me with this C program