C 二级指针和三级指针的使用

//这里给出三级指针作为参数和二级指针作为参数的demo

//三级指正作为参数，内存分配在函数内

//二级指针作为参数，内存分配在函数外，也就是调用的地方

#include <string.h>#include <stdlib.h>#include <stdio.h>#include <iostream>#include <string>#include <vector>using namespace std;void func(char*** args, int &c){    int count = 3;    c = count;    const char *iface[] = {"getStatus", "setStatus", "getUserName"};    *args = (char**)malloc(count*sizeof(char*));    for( int i = 0; i < count; i++ )    {        cout << iface[i] << endl;        int len = strlen(iface[i])+1;        (*args)[i] = (char*)malloc(len*sizeof(char));        memset((*args)[i], 0, len);        strcpy((*args)[i], iface[i]);    }}void func2(char**args, int &num, int* lens){    int count = 3;    const char *iface[] = {"getStatus", "setStatus", "getUserName"};    num = count;    for( int i = 0; i < count; i++ )    {        lens[i] = strlen(iface[i]);    }    if( args == NULL )        return;    for( int i = 0; i < count; i++ )    {        strcpy(args[i], iface[i]);    }}int main(){    char **array = NULL;    int count = -1;    func(&array, count);    vector<string> ifaceList;    cout << "count = " << count << endl;    for( int i = 0; i < count; i++ )    {        cout << array[i] << endl;        ifaceList.push_back(array[i]);        if( array[i] != NULL )        {            free(array[i]);            array[i] = NULL;        }    }    if( array != NULL )    {        free(array);        array = NULL;    }    cout << "----------------" << endl;    for( vector<string>::iterator iter = ifaceList.begin(); iter != ifaceList.end(); iter++ )    {        cout << *iter << endl;    }    cout << "======= who allocate who free ==========" << endl;    char** pIfaceList = NULL;    int num = -1;    int lens[100] = {-1};    func2(pIfaceList, num, lens);    cout << "num = " << num << endl;    for( int i = 0; i < num; i++ )    {        cout << "len[" << i << "] = " << lens[i] << endl;    }    //allocate memory    pIfaceList = (char**)malloc(num*sizeof(char*));    for(int i = 0 ; i < num; i++)    {        int nLen = lens[i]+1;        pIfaceList[i] = (char*)malloc(sizeof(char)*nLen);        memset(pIfaceList[i], 0, sizeof(char)*nLen);    }    func2(pIfaceList, num, lens);    vector<string> ifaceList2;    for( int i = 0; i < num; i++ )    {        cout << "pIfaceList[" << i << "] = " << pIfaceList[i] << endl;        ifaceList2.push_back(pIfaceList[i]);        free(pIfaceList[i]);        pIfaceList[i] = NULL;    }    if( pIfaceList != NULL )    {        free(pIfaceList);        pIfaceList = NULL;    }    return 0;}