char *p1=malloc(1000);
p1 += 1000;
*p1 = 0; //どかーん

int *p2=(int *)malloc(1000);
p2 += 500;
*p2 = 0; //ちゅどーん

char *p3=malloc(1000);
p3++;
free(p3); //ｵｶｰｻｰﾝ