C How to Free a Pointer Example

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

void freePointer(int** pointer);

int main()
{
    int* pointer = (int*)malloc(sizeof(int));
    *pointer = 10;

    printf("pointer 的數值 = %p\n", pointer);
    printf("對 pointer 取值 = %d\n", *pointer);
    printf("====== 釋放 pointer ======\n");
    /*
    free(pointer);
    printf("pointer 的數值 = %p\n", pointer);
    printf("對 pointer 取值 = %d\n", *pointer);
    printf("===== pointer 為 NULL ====\n");
    pointer = NULL;
    printf("pointer 的數值 = %p\n", pointer);
    printf("對 pointer 取值 = %d\n", *pointer);
    */
    freePointer(&pointer);
    printf("pointer 的數值 = %p\n", pointer);
    printf("對 pointer 取值 = %d\n", *pointer);

    return 0;
}


void freePointer(int** pointer)
{
    free(*pointer);
    *pointer = NULL;
}

/***************************** 執行結果 ******************************
pointer 的數值 = 00872F88
對 pointer 取值 = 10
====== 釋放 pointer ======
pointer 的數值 = 00000000

Process returned -1073741819 (0xC0000005)   execution time : 4.984 s
Press any key to continue.
*********************************************************************/