Thread: void *ptr problem

hey guys it was my first time using void as parameter my code fails hardly though i dunno whats the problem in failing
i m srry had problem in return code

Code:

#include <stdio.h>
#include <stdlib.h>
#define array_num 100
int allocating_memory_func(void *stuff,int num,int num2)
{
	stuff=malloc(num2 * num);
	if(stuff==NULL) 
		return 0;//func failed
	return 1;//function is cool
	
}
int main(void)
{
    int x;
    int *y;
	if(!allocating_memory_func(y,array_num,sizeof x)){
		free(y);
        puts("Function failed");
        getchar();
        exit(0);}
  else{
       for(x=0;x<array_num;x++){
        fputs("Please enter your num: ",stdout);
        scanf("%d",x[y]);}
    for(x=0;x<array_num;x++){
        printf("num %d is in array %d",x,x[y]);
	}
}
	getchar();
    return getchar();
}

Your code fails because you cannot change what a pointer points AT unless you use a pointer to that pointer. Pointers are just like any other variable. They store a piece of information. In the case of pointers, that pointer is an addres.

To change what a passed variable contains, so that it is reflected in the calling function, you have to have a pointer to what you want to change.

If you want to change an int, you need a pointer to an int.
If you want to change a pointer, you need a pointer to that pointer.

Oh, and stop using fflush on input streams.


Quzah.

Where exactly are you initializing it?

Originally Posted by lolguy

but ptrs to void can be ptrs to anything

Close, but not quite. But what does this have to do with anything?

Quzah.

You aren't initializing it before passing it to the function, so why would it be initialized once it arrives? If you aren't familiar with the term, "initalizing" means "providing a value". Like so:

Code:

int x;
x = 5; /* here we are initializing x by giving it a value of 5 */

Here we use it without initializing it.

Code:

int x;
x++; /* increment x ... but wait, what value did it have before we added one to that? */

Quzah.

No. Otherwise your compiler wouldn't be yelling at you about it.


Quzah.