参数是指针，传递指针变量，最后函数总分配的内存丢了

void allcMem(int *a, int n){
    a = (int*)malloc(n*sizeof(int));
    for (int i = 0; i < n; i++){
        a[i] = 0;
    }//end for
}//end fucntion allcMem

int main(int argc, char** argv){
    int *pi = NULL;
    int arr[] = { 1, 1, 1, 1, 1, 1, 1 };
    pi = arr;
    allcMem(pi,5);
    for (int i = 0; i < 7; i++){
        printf("%d  ",pi[i]);
    }//end for
    printf("\n");
    system("pause");
    return 0;
}//end main

上面的代码最后的结果是 输出七个1，而不是5个0

#include<stdio.h>
#include<stdlib.h>
#define N 10

void allcMem(int **a, int n){
    *a = (int*)malloc(n*sizeof(int));
    for (int i = 0; i < n; i++){
        (*a)[i] = 0;
    }//end for
}//end fucntion allcMem



int main(int argc, char** argv){
    int *pi = NULL;
    int arr[] = { 1, 1, 1, 1, 1, 1, 1 };
    pi = arr;
    allcMem(&pi,5);
    for (int i = 0; i < 5; i++){
        printf("%d  ",pi[i]);
    }//end for
    printf("\n");
    system("pause");
    return 0;
}//end main

这样才是正确的代码