Thread: How to assign values to dynamic memory

I have allocated memories for five integer variables. I want to store values 1, 3, 10, 9, 5

Code:

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


int main ()
{
   int *var = malloc( 5 * sizeof(int));
   
   if ( var != NULL )
   {
	   
   }
	return 0;
}

I don't understand how to store all values in allocated space ?

Originally Posted by Kittu20

I don't understand how to store all values in allocated space ?

Well Salem presented the easiest way but you could also used pointer arithmetic to access the allocated memory.

Originally Posted by Salem

The same way you would with an array of 5 elements.

var[0] = 1;
var[1] = 3;
etc.

I have allocated space for only five integers , so only five values should be store, why are last two variables being stored ?

Code:

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


int main ()
{
   int *var = malloc( 5 * sizeof(int));
   
   if ( var != NULL )
   {
	   var[0] =  1;
	   var[1] =  3;
	   var[2] =  10;
	   var[3] =  9;
	   var[4] =  5;
	    
	   var[5] =  15;
	   var[6] =  50;
	   
    for ( int i = 0; i < 7; i++)
	{
	      printf("%d ", *var);
	       var++;
	}
   }
	return 0;
}

1 3 10 9 5 15 50

Originally Posted by Salem

> for ( int i = 0; i < 7; i++)
Later on, you would likely feel the pain when
- you tried to free the memory
- you tried to allocate more memory.

I allocated memory for three variables, then allocated for two variables and then freed allocated memory

Code:

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


int main ()
{
  // Memory allocate for 3 variables 	
  int *var = malloc(3* sizeof(int));
  
  if ( var != NULL )
  {
	var[0] =  10;
	var[1] =  3;
	var[2] =  9;
  }
  
  // memory allocate for more two variables, total memory allocated for five variables  
  var = realloc(var, 5 * sizeof(int)) ;
  
  if ( var != NULL )
  {
	var[3] = 9;  
	var[4] = 5;
	
	printf(" %d", *var);
  }
  
  free(var); 
  
  printf(" %d", *var); 


  return 0;
}

10 10

I don't understand why the value is stored even after the memory is freed