Thread: Going blind can't see my error, please help.

Hey guys I just started coding in C, so i'm no up to par with everything. I've been writing a program that deals with structs and linked lists, and I've run into an "imcompatible type in assignment" error and I can't see what's going on because I've been looking at this code for 1.5 hrs now. please help me. Thanks!

here's my func file

Code:

#include <stdio.h>
#include <stdlib.h>
#include "funcs.h"


LIST_ELEM *add(LIST_ELEM *pHead,char type[],char name[], char title[], int year, int price, int size){

	LIST_ELEM *new_elem = malloc(sizeof(LIST_ELEM));

	new_elem->type = type;
	new_elem->name = name;
	new_elem->title = title;

	new_elem->year = year;
	new_elem->price = price;
	new_elem->size = size;

	return new_elem;

}

my header

Code:

typedef struct list_elem
{
	char type[5];
	char name[50];
	char title[50];
	int year;
	int price;
	int size;
	struct list_elem *pNext;
}LIST_ELEM;

LIST_ELEM *add(LIST_ELEM *pHead,char type[],char name[], char title[], int year, int price, int size);
int size(LIST_ELEM *phead);
LIST_ELEM *find(LIST_ELEM *pHead, int value);
void print(LIST_ELEM *pHead);

and my main (its a noob program, but i'm a noob so its ok )

Code:

#include <stdio.h>
#include <stdlib.h>
#include "funcs.h"

int main(void){

  LIST_ELEM *pHead = NULL;
  char type[5];
  char name[50];
  char title[50];
  int year;
  int price;
  int size;

  int choice;

  do {
	printf("What would you like to do? \n\n");
	printf("0. Exit \n");
	printf("1. Print books/cds. \n");
	scanf("%d", &choice);

	switch(choice){
	  case 1:
	  	print(pHead);
		break;
	  case 2:
		printf("Enter 'book' or 'cd' for type: \n");
		scanf("%s", &type);
		printf("Enter name of author/artist: \n");
		scanf("%s", &name);
		printf("Enter title: \n");
		scanf("%s", &title);
		printf("Enter year published/released: \n");
		scanf("%d", &year);
		printf("Enter price: \n");
		scanf("%d", &price);
		printf("Size of book/cd: \n");
		scanf("%d", &size);

		pHead = add(pHead,type,name,title,year,price,size);
		break;
		
			}
		}while(choice != 0);
	return 0;
}

I know it has to do with the passing in of character string for my add() method, but I don't know what the right syntax is to get it to work. Thanks again!

You can't copy strings with "=" (as in new_elem->type = type), you must use strcpy.

The problem is when you're attempting to fill your struct...

new_elem->type = type

The string array type is passed to your function as a pointer only. You want to save the contents of that string... so use

strcpy(new_elem->type, type)

... which moves the actual characters.... Hopefully the destination array sizes are always large enough to accommodate the user's input. This is a common "bug", when an evil user (aren't they all?) writes and writes and writes, and causes your program to overshoot the destination array.

It's called a header file. Yes, it's a good idea to include that whenever you use any string functions.

Sorry I edited but it didn't work.

When I type in a string of size larger then 7 letters it skips a couple printfs.

so say for title i put in : the cat and the hat

it jumps over the author and goes right to the publish date. But it doesn't make sense since i allocate sizes of 50 for the title and 50 for the author.

But five characters works fine? Are you sure you don't have %7s or something like that in your program?

yeah pretty sure.

if i put in

name: heres myname

its skips down to date published:

but when i do a print out of it
i get

name: heres
title: name

Yeah I can't replicate the "skipping printfs" at all. I did notice that the new_elem->pNext is not being updated... to link the malloced elements together. But that's not the issue at the moment.

No wait.... if I enter in anything which has spaces in it, the scanf absorbs it into the numbers.... I should have seen that coming. It's late in the day.

Originally Posted by TaiL

yeah pretty sure.

if i put in

name: heres myname

its skips down to date published:

but when i do a print out of it
i get

name: heres
title: name

Ha ha! It's not five characters -- it's the space. %s stops at any whitespace (spaces, tabs, or enter key). To read the whole line, use fgets.

(Note to reader: Ha ha! must be given your best over-dramatic villain interpretation.)

thanks. for that one. Interesting how you don't get the skipping printfs.

No I do.... sort of. They go flying by real fast because their associated inputs are already satisfied. No waiting at the keyboard for those.

Not too sure with fgets

from what i can understand fgets takes in a (str,int, file);

but in my case i don't have a file so can I leave file blank?

Your file is stdin.

so instead of

Code:

printf("Enter title: ");
scanf("%s", &title);

i do

Code:

printf("Enter title: ");
fgets(&title,50, stdin);

so then I don't have to declare the size of the char array at the beginning of my file then?