Standard C Episode 10

标准库函数malloc/calloc/realloc以及free的堆内存分配与回收

/*
 * malloc练习
 *
 * */

#include <stdlib.h>
#include <stdio.h>

int main()
{
    int *p_value = NULL;

    p_value = (int *) malloc (1 * sizeof(int));
    if (p_value) {
        printf(" p_value是0x%p\n",  p_value);
        printf("*p_value是%d\n", *p_value);
        free(p_value);
        p_value = NULL;
    }
    }

    return 0;
}

 

 

/*
 * calloc(), realloc()练习
 *
 * 不同于malloc,calloc会将把开辟的存储空间初始化为零
 *
 * */

#include <stdlib.h>
#include <stdio.h>

int main()
{
    int *p_value = (int * ) calloc(4, sizeof(int));
                //(int * )   malloc(4 * sizeof(int));
    if (p_value) {
        printf(" p_value是0x%p\n", p_value);
        printf("*p_value是%d\n", *p_value);
        void *pointer = NULL;
        pointer = realloc(p_value, 6 * sizeof(int));
            //realloc(p_value, 0);实际效果就等于语句free(p_value);
            //p_value = NULL, realloc(p_value, 4*sizeof(int));实际效果就
           //等于语句p_value = NULL, p_value = (int *)malloc(4*sizeof(int));
        if (pointer) {
            p_value = (int * )pointer;
        }
        printf(" p_value是0x%p\n", p_value);
        printf("*p_value是%d\n", *p_value);
        free(p_value);
        p_value = NULL;
    }
}

 

 

/*
 * Input: 1234
 * Output: 4321
 * */

#include <stdio.h>
#include <stdlib.h>

int main()
{
    typedef enum {N, Y} en_retry;

    en_retry over = N;
    int *p_integer = NULL;
    int *p_integers[100] = {NULL};

    int counter = 0;
    do {
        p_integer = (int *) malloc(sizeof(int) * 1);
        if (p_integer) {
            printf("Input an Integer");
            scanf("%d", p_integer);
            p_integers[counter++] = p_integer;
        }
        printf("Another?[Y/N]");
        printf("%d\n", over);
        scanf("%d", &over);
        printf("%d\n", over);
    } while (over);

    for (--counter; counter >= 0; counter--) {
        printf("%d\t", *p_integers[counter]);
        free(p_integers[counter]);
    }
    printf("\n");

    return 0;
}