still available even after freeing dynamic allocated memory

[perlsu]

I would like to know whether the dynamic memory pointer is still available even after freeing the allocated memory. If I want to allocate and deallocate so many times within a loop , I receive memory corruption. Pls help me how I should do.If I call "free" more than one time, it reports error because allocated memory is already freed even though there is still available. I don't understand this concept . Pls help me.The program is as follows.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void main()
{
int i = 0;
unsigned char* temp = NULL;
unsigned char st[] = "Hello";
for ( i = 0;i < 10;i++)
{
temp = (unsigned char*) malloc( strlen(st) );
memcpy( temp, st, strlen(st));
if (temp)
free(temp);
if (temp)
printf("still available");
else
printf("already destroyed");
if (temp)
free(temp);
}
}

[Bench]

when you "free" memory, you are deleting the object which "temp" points to, you are not modifying temp itself. What you are left with is a dangling pointer which points to some undefined part of memory, which could contain absolutely anything. you should assign the value of NULL to "temp" after freeing the memory.

[Narue]

>I would like to know whether the dynamic memory pointer is still
>available even after freeing the allocated memory.
No, it's not. When you free memory, you must reassign the pointer to memory that you own before you can dereference it again.