Void Pointers & Malloc & Free Sample

VoidPointers.c

#include <stdio.h>
#include <stdlib.h>	/* for malloc function */
#include <string.h> /* memcpy */

int main()
{
	void *p = malloc(4);	/* 4 bytes requested */
	
	if(!p)
	{
		printf("Memory allocation failed, program halted...\n");
		return 1;
	}
	
	printf("****************************************************\n");
	
	printf("size of int : %d\n", sizeof(int));
	
	/* Use 4 byte for 1 integer */
	*(int*)p = 1982;
	printf("Content of void pointer : %d\n", *(int*)p);
	
	printf("size of \"Lev\" string: %d\n", sizeof("LeV"));
	
	/* Use 4 byte for 3 char and a null-terminator */
	memcpy(p, "LeV", 4);

	printf("Content of void pointer : %s\n", (char *)p);
	printf("Content of void pointer : %c%c%c\n", *(char *)p, *(char *)(p+1), *(char *)(p+2));
	printf("Content of void pointer : ");
	
	int i; /* c89 standard compiler used */
	void * pp = p;
	for(i = 0; i<3; i++)
	{
		printf("%c", *(char *)pp++);
	}
	pp = 0;
	
	printf("\n");
	printf("****************************************************\n");
	printf("\n");
	
	if(p)
	{
		free(p);
		p = 0;
	}
	
	return 0;
}