Thread: Malloc, Realloc and Calloc Help/Suggestion

Code:

#include <stdio.h>
#include <stdbool.h>
#include "project1.h"


int main()
{
int i, r, NUM_ITEMS, t, ret, ava;
int*  numbers;
NUM_ITEMS = 0;
ava = 100;



numbers =  malloc(100 * sizeof(int));
while(((ret = scanf("&#37;d",&t)) != EOF) && (ret != 0))
{   
    if (NUM_ITEMS <= ava)
    {
	numbers[NUM_ITEMS] = t;
	NUM_ITEMS++;
} else
{
 numbers = realloc(numbers, sizeof(numbers) + sizeof(int)*100);
 ava = ava + 100 ;  
 printf("%d\n",t);
	numbers[NUM_ITEMS] = t;
	printf("\t Array at %d = %d\n",NUM_ITEMS, numbers[NUM_ITEMS]);
	NUM_ITEMS++;
}    	
 
 
}
 
r = bubbleSort(numbers, NUM_ITEMS);
	 
r =  insertionSort(numbers, NUM_ITEMS);
 
}

I am doing a proj for class. the point is to make some sort function and let them have at. The problem is I am having issues with malloc. I though I understood the memory alloction stuff pretty well but when ever I try to run this on a file with alot of numbers (say 100000) I run into memory issues and the computer I am compiling on gets all upset. I have the sorts running and sorting the same number of element when I use a a size I define in the code.

So, my question is, is my problem a result of the way I am mallocing here or should I look at me calloc call in my sorts or is it the computer?

Here is an example of a sort

Code:

/*********************************************************
int bubbleSort(int * a, int n);

*********************************************************/
int bubbleSort(int * number, int array_size)
{
int i, j, r, temp;
int * array_sort;	

	//Allocating array of same size as passed array.
	array_sort = (int *)calloc(array_size,sizeof (int));

	if(array_sort != NULL)
	{
	//printf("Array created of size \n",array_size);
        }
        else
        {
                //printf("Not enough memory\n");
                exit(1);
        }
// Bubble Code
	
// Clean-up
 free (array_sort);   
	return(0);
}

Thanks for any suggestion

Does this work?

Code:

#include<stdlib.h>
int main( void )
{
    int *numbers = malloc( 100000 * sizeof *numbers );
    if( number )
        free( numbers );
    return 0;
}

Or does it crash? I really doubt your issue is with malloc. You're probably blowing your stack space all to hell.


Quzah.

Here are a couple of Things Not To Do:

Code:

while(((ret = scanf("%d",&t)) != EOF) && (ret != 0))
{   
    if (NUM_ITEMS <= ava)

It would be better to check the scanf attempt against success; i.e., check whether the return value is 1. But that's just my footnote; you do check, but in an unnecessary manner.

And arrays of size N may be indexed from 0 to N-1. The <= goes one beyond the end of the array.

Originally Posted by zensatori

So, my malloc ing looks ok?

That depends. What doe sizeof( int ) give you? It's possible that 100,000 won't fit in your int.


Quzah.

> numbers = realloc(numbers, sizeof(numbers) + sizeof(int)*100);
Well this doesn't expand your array by 100 ints, not by a long way.

sizeof(numbers) just tells you the pointer size, not how much memory you're pointing at.

Expanding on that: sizeof(numbers) is like saying sizeof(int *), which will probably be 2 or 4. You probably want to use ava * sizeof(int) or something.