The C/C++ library function void free(void *ptr) deallocates the memory previously allocated by a call to calloc, malloc, or realloc. Following is the declaration for free() function.
void free(void *ptr)
This function takes a pointer ptr. This is the pointer to a memory block previously allocated with malloc, calloc or realloc to be deallocated. If a null pointer is passed as argument, no action occurs.
Example
#include <iostream>
#include <cstdlib>
#include <cstring>
using namespace std;
int main () {
char *str;
/* Initial memory allocation */
str = (char *) malloc(15);
strcpy(str, "tutorialspoint");
cout << "String = "<< str <<", Address = "<< &str << endl;
/* Reallocating memory */
str = (char *) realloc(str, 25);
strcat(str, ".com");
cout << "String = "<< str <<", Address = "<< &str << endl;
/* Deallocate allocated memory */
free(str);
return(0);
}Output
String = tutorialspoint, Address = 0x22fe38 String = tutorialspoint.com, Address = 0x22fe38