传递参数并给它们值会导致运行时错误 [英] Passing parameters and giving them values causes runtime error

问题描述

所以我有以下代码：

void emptyString(char* token, int size) {
    for (int i=0; i < size; i++) token[i] = '\0';
}

    void setDefaults(char uloginName[], char *home_directory, char *password, char *shell, char *gecos) {
        emptyString(home_directory, sizeof(home_directory) - 1);
        strcat(home_directory, "home/home/");
        strcat(home_directory, uloginName);
    }

    int main(){
        char buffer[256];
        AccountInfo *tempAccount;
        UserDB users;
        char uloginName[9] = "Smith";
        char homeDirectory[33];
        int userID;
        int groupID;
        char password[17];
        char shell[17];
        char gecos[65];
        int i, j, k;
        char flag[3];
        char IDString[6];
        char command[11];
        char blank = ' ';

    setDefaults(uloginName, homeDirectory, password, shell, gecos);
    return 0;
    }

当我在Visual Studio中运行此代码时， / p>

When I run this code in Visual Studio I get a pop up window saying

运行时检查失败＃2 - 堆叠变量'users'是
已损坏

Run-Time Check Failure #2 - Stack around the variable 'users' was corrupted

这是由于 setDefaults（）方法中的代码行引起的。我希望有人帮助我更正代码。我的目的是将home_directory的值设置为home / home / userloginname ，其中userloginname也是传递的变量之一。

This is caused due to the lines of codes in the setDefaults() method. I was hoping someone helped me to correct the code. My intention is to set the value of home_directory to "home/home/userloginname" where userloginname would be one of the variables being passed as well.

EDIT：我刚刚发现我的代码中的prolem是 strcat（）方法。如果我使用 strcpy（）的第一个，它工作正常，但一旦我想添加更多，它显示一个弹出窗口说，变量用户已损坏。下面是userDB类的代码：

I just found out the prolem in my code is the strcat() method. If I use strcpy() for the first one, it works fine, but once I want to add more, it shows me a pop up window saying that the variable users got corrupted. Here is the code for the userDB class:

class UserDB
{
private:
    AccountInfo* _accounts[200]; // store up to 200 accounts
    unsigned int _size; // number of account stored
    unsigned int _nextUid; // next user id to be assigned
    unsigned int _defaultGid; // default group id
    // other private methods necessary for this class
public:
    // constructors(empty), destructor
    void adduser( AccountInfo* newUser);
    void    showUsers();
    void    showPasswd();
    void    finger(char* userLoginName);class
    int size(); // return the number of accounts stored (_size)
    // and other public methods (mutators/setters, accessors/getters)
};

代码现在是，因为它在这里。也许我需要做构造函数或析构函数或者什么，但作为一个新手，因为没有办法知道是什么实际上导致错误，需要修复。

the code is, right now, as it is in here. Perhaps I need to make the constructor or destructor or whatnot, but as a newbie as have no way of knowing what is actually causing the error and needs to be fixed.

编辑：所以经过很长时间我发现strcat（）是什么原因导致的错误，但是我需要做strcat声称做的事情。这是我的完整代码的副本 http://ideone.com/A5iWh ，以便有兴趣的人可以让我知道什么改变，因为我不知道还有什么要做。感谢。

So after a long while I found out strcat() is what is causing the error, however I need to do what strcat claims to do. Here is a copy of my complete code http://ideone.com/A5iWh so that whoever is interested can let me know what to change because I do not know what else to do. Thanks.

推荐答案

显着的问题：

// in getNextToken
while ((buffer[i] != delimeter) && (i < 256) && (j < tokenSize))
    token[j++] = buffer[i++];

没有检查您是否已到达 [] ，而不是长度检查。如果 cin.getline（buffer）读取用户名p mypasswd？然后：

在第150行，复制到命令填写命令终止null。也许这不是一个问题...

在第153行，读入 uloginName 也不插入终止空字符。

在第170行，读入密码读取16个字节。也许你会得到一个空终止符运气，如果密码足够短。

There's no check that you've reached the end of the contents of buffer[], other than a length check. What if cin.getline(buffer) were to read "a username p mypasswd"? Then:

at line 150, the copy into command fills up command but never puts a terminating null at the end. Maybe this isn't a problem...

at line 153 the read into uloginName also doesn't insert a terminating null character.

at line 170 the read into password reads 16 bytes. Maybe you'll get lucky with a null terminator, if the password was short enough.

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