报错一直运行不出来，求解

Question

#include <iostream>
#include"stdafx.h"
#include"winsock2.h"
#include<tchar.h>
#include <string>
using namespace std;
#pragma comment(lib,"ws2_32.lib")
int _tmain(int argc, _TCHAR* argv[]) {
    if (argc != 3) {
        printf("Usage: CalculateSubnet netaddr netmask\r\nExample:CalculateSubnet 192.168.0.0 255.255.255.0");
        return 1;
    }
    bool IsValidIP(char* ip);{
        std::string sip = ip;
        int pos = (int)sip.find_first_of(".");
        if (pos == 0)return false;
        std::string s1 = sip.substr(0, pos);
        sip = sip.substr(pos + 1, sip.length() - pos);
        if (s1.length() > 3) return false;
        for (int i = 0; i < (int)s1.length(); i++) {
            int c = s1.c_str()[i];
            if (!isdigit(c))return false;
        }
        int a = atoi(s1.c_str());
        if (a < 1 || a>255)return false;
        pos = (int)sip.find_first_of(".");
        std::string s2 = sip.substr(0, pos);
        sip = sip.substr(pos + 1, sip.length() - pos);
        if (s2.length() > 3) return false;
        for (int i = 0; i < (int)s2.length(); i++) {
            int c = s2.c_str()[i];
            if (!isdigit(c))return false;
        }
        a = atoi(s2.c_str());
        if (a > 255)return false;
        pos = (int)sip.find_first_of(".");
        std::string s3 = sip.substr(0, pos);
        sip = sip.substr(pos + 1, sip.length() - pos);
        if (s3.length() > 3) return false;
        for (int i = 0; i < (int)s3.length(); i++) {
            int c = s3.c_str()[i];
            if (!isdigit(c))return false;
        }
        a = atoi(s3.c_str());
        if (a > 255)return false;
        pos = (int)sip.find_first_of(".");
        std::string s4 = sip.substr(0, pos);
        sip = sip.substr(pos + 1, sip.length() - pos);
        if (s4.length() > 3) return false;
        for (int i = 0; i < (int)s4.length(); i++) {
            int c = s4.c_str()[i];
            if (!isdigit(c))return false;
        }
        a = atoi(s4.c_str());
        if (a > 254)return false;
        return true;
    }
    if (!IsValidIP(argv[1])) {
        printf("%s is not a valid ip.\n", argv[1]);
        return 1;
    }
    if (!IsValidIP(argv[2])) {
        printf("%s is not a valid ip.\n", argv[2]);
        return 1;
    }
    printf("netaddr:%s\n", argv[1]);
    printf("netmask:%s\n", argv[2]);
    unsigned long lnetaddr = ntohl(inet_addr(argv[1]));
    unsigned long lnetmask = ntohl(inet_addr(argv[2]));
    unsigned long l_first_netaddr = lnetaddr & lnetmask;
    unsigned long l_broadcast = lnetaddr | ~lnetmask;
    long num = l_broadcast - l_first_netaddr - 1;
    printf("Number of valid IPs:%d\n\n", num);
    printf("IPs in subnet:\n===============\n");
    for (unsigned long i = l_first_netaddr + 1; i < l_broadcast; i++) {
        in_addr IPAddr;
        IPAddr.S_un.S_addr = ntohl(i);
        printf("%s\n", inet_ntoa(IPAddr));
    }

Answer 1

bool IsValidIP(char* ip);
你这是定义还是调用？？？
整个语法都不通