C语言操作内存

炒了个栗子

#include <stdio.h>
#define N1 (5)
#define N2 (7)
#define N3 (3)

int main(){
        int *ip;
        int *large_ip;
        int *small_ip;
        //内存空间的首地址
        ip = (int *)malloc(N1*sizeof(int));
        if(ip == NULL){
                printf("memory allocated failed\n");
                exit(1);
        }
        int i;
        for(i=0;i<N1;i++){
                ip[i] = i;
                printf("ip[%d] = %d\t", i, ip[i]);
        }
        printf("\n");

        large_ip = (int *)realloc(ip,N2*sizeof(int));
        if(large_ip == NULL){
                printf("memory allocated failed!\n");
                exit(1);
        }
        for(i=N1;i<N2;i++){
                large_ip[i]=9;
        }

        for(i=0;i<N2;i++){
                printf("large_ip[%d] = %d\t", i, large_ip[i]);
        }
        printf("\n");
        small_ip = (int *)realloc(large_ip,N3*sizeof(int));
        if(small_ip == NULL){
                printf("memory allocated failed!\n");
                exit(1);
        }
        for(i=0;i<N3;i++){
                printf("small_ip[%d] = %d\t", i, small_ip[i]);
        }
        printf("\n");
        ////手动释放内存
        free(small_ip);
        return 0;
}