Stack Problem

[noroi]

Hi, I need your help with this one.
I created a stack program but there is a problem.
The program doesn't seem to add data into the push function.

/*
 *Stack
 *C
 *
 */ 


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




typedef struct stack Stack;


struct stack{
   int data;
   Stack *next;     
};




void push(Stack *, int);
int pop(Stack *);
int is_empty(Stack *); //
void print_stack(Stack *);
void instructions(void);


int main(void)
{
   Stack *node = NULL;
   int choice;
   int value;
   
   instructions();
   printf("?");
   scanf("%d", &choice);
   
   while(choice != 3)
   {
      switch(choice)
      {
         case 1:
            printf("\nEnter an integer => ");
            scanf("%d", &value); 
            push(node,value); 
            print_stack(node); 
            break; 
             
         case 2:
            if(!is_empty(node))
            {
               printf("\nThe popped value => %d", pop(node));                   
            }      
            print_stack(node);
            break;
            
         default:
            printf("\nInvalid choice\n\n");
            instructions();
            break;              
      }
   printf("?");   
   scanf("%d ", &choice);         
   }
   printf("End Of Run!\n");
   return 0;   
}


void push(Stack *node, int value)
{
   Stack *new_node;
   new_node = (Stack *)malloc(sizeof(Stack));
   
   if(new_node != NULL)
   {
      new_node->data = value;
      new_node->next = node;
      node = new_node;            
   }    
   else printf("No available memory fo %d\n", value);
}
int pop(Stack *node)
{
    Stack *temp;
    int value;
    
    temp = node;
    value = node->data;
    node = node->next;
    free(temp);
    
    return value;
}


int is_empty(Stack *node)
{
   return node == NULL;   
}


void print_stack(Stack *node)
{
   if(node == NULL)
   {
      printf("The stack is empty.\n\n");        
   }
   else
   {
      printf("Tha stack is: \n");    
      while(node != NULL)
      {
         printf("%d --> ", node->data);
         node = node->next;
      }
      printf("NULL\n\n");
   }
}


void instructions(void)
{
   printf("Enter choice => \n"
                 "1 push\n"
                 "2 pop\n"
                 "3 end\n");    
}

Can somebody tell me what's wrong?

[DRK]

node = new_node;

That changes value of node pointer only in push() function.

The are 2 ways to fix it:
1. By passing pointer to Stack pointer

void push(Stack **node, int value)
{
   Stack *new_node;
   new_node = malloc(sizeof(Stack)); // no type-cast needed here
   if(new_node != NULL)
   {
      new_node->data = value;
      new_node->next = *node;
      *node = new_node;
   }
   else printf("No available memory fo %d\n", value);
}

2. By returning new pointer.

Stack *push(Stack *node, int value)
{
   Stack *new_node;
   new_node = malloc(sizeof(Stack)); // no type-cast needed here
   if(new_node != NULL)
   {
      new_node->data = value;
      new_node->next = node;
   }
   else printf("No available memory fo %d\n", value);
   return new_node;
}

[noroi]

i understand now, you've been a great help.

on your comment, it says no type-cast needed.
why and when do i need to do type-casting ?
i need clarifications!

[vart]

on your comment, it says no type-cast needed.
why and when do i need to do type-casting ?

in C

void* pointer could be assigned to any other pointer without cast, and the opposite.

since malloc returns void* its result could be assigned to any pointer without cast
Removing cast also provides additional help in verifying that required include is not missing
FAQ > Casting malloc - Cprogramming.com