[SOLVED] Error with GCC

dracuss · 04-02-2009, 01:43 AM

Here is the problem: I'm trying to exercise on binary trees in C, and I've made the following function that would create a binary tree:

Code:

NODE * create(void)
{NODE *p;
 int f;
 //system("cls");
 if (idform==1000)
 {printf("THE ROOT");}
  printf("\n\nDo you want to create?  (1/0)\nAswer:  ");
  scanf("%i",&f);
  if (!f) return NULL;
  p=(NODE*) malloc (sizeof(*p));
  //system ("cls");
  printf("\nEnter info:\n\n");
  printf("\nAn id for the node will be generated automatically.\n");
     p->IDindex=idform;
     printf("The ID is: %i",p->IDindex);
     printf("\nEnter info of the node: \n");
     printf ("Model: ");
	 fflush(stdin);
	 gets(p->model);
	 printf ("Country: ");
	 fflush(stdin);
	 gets(p->country);
	 fflush(stdin);
	 printf ("Date of production: ");
	 fflush(stdin);
	 gets(p->date);
	 printf ("Horsepower: ");
	 scanf("%d",&p->hp);
	 printf("Price : ");
	 scanf("%d",&p->price);
	 idform++;

  printf("\n\nLeft child for node %i",p->IDindex);
  p->left=create();
  printf("\n\nRight child for node %i",p->IDindex);
  p->right=create();
 return p;
}

The error that I get is that always the "model" field cannot be introduced from keyboard. This is what I get when running the soft:

Code:

Do you want to create?  (1/0)
Aswer:  1

Enter info:


An id for the node will be generated automatically.
The ID is: 1000
Enter info of the node: 
Model: Country: 2
Date of production: 2
Horsepower: 2
Price : 2

bigearsbilly · 04-02-2009, 03:44 AM

I wouldn't use scanf.
use gets and convert.

just a thought...
C is crap for user interfaces.
why don't you leave the user input out?
make a shell wrapper, or even a wish script, and pass the input in from that.
it's a lot easier to format the input correctly first then pass it in.

wje_lq · 04-02-2009, 05:48 AM

Quote:

Originally Posted by bigearsbilly

I wouldn't use scanf.

I agree wholeheartedly.

Quote:

Originally Posted by bigearsbilly

use gets and convert.

*facepalm*

Never ever ever use gets(), because it doesn't allow you to specify the maximum number of bytes in your input. Exploiting buffer overflow bugs (and the use of gets() is always a bug) is the leading cause of malware and also of tooth decay.

Never ever. Instead, use fgets().

johnsfine · 04-02-2009, 07:52 AM

I don't want to disagree with either of the first two answers. Both make good points. But I don't see the answer to the actual question in there anywhere.

I'm not sure myself the exact rules for when output from printf actually reaches stdout vs. when it is buffered. (I don't use printf much). But the quoted program output makes it look like the prompt/input is out of sync by one position because of that buffering.

Maybe you need to fflush(stdout) after any printf that you want displayed immediately.

dwhitney67 · 04-02-2009, 08:12 AM

As the thread title indicates, the problem is with GCC.

@ OP

Fix your initial scanf() to discard unwanted characters, or in your case, a newline.

Code:

  printf("\n\nDo you want to create?  (1/0)\nAswer: ");
  scanf("%i%*c", &f);
  ...

When reading a string, use fgets().

Code:

fgets(str, sizeof(str), stdin);