c++ - 我在以下代码中收到总线错误

Question

我的代码中出现总线错误。使用此代码，我试图将数字转换为单词，但我知道我的逻辑存在缺陷。但在此之前，当我在 Mac 上使用 g++ 编译并运行此代码时，我试图让这段代码按原样运行，但出现总线错误。任何帮助将不胜感激。

当我运行代码时，我得到以下输出。我有调试消息来跟踪错误发生的位置。

    Enter a number:1234    main 1:numbers are:234    Function1: Number is 234    two    two hundred    34Function2: Number is 34    Function3: Number is 34    Bus error: 10

---

#include <iostream>
#include <string>

using namespace std;
char *convert_number(int);

char *tens[] = {"", "ten", "twenty", "thirty", "forty",
                "fifty", "sixty", "seventy", "eighty", "ninety"};

char *words[] = {"zero", "one", "two", "three", "four",
                 "five", "six", "seven", "eight", "nine",
                 "ten", "eleven", "twelve", "thirteen", "fourteen",
                 "fifteen", "sixteen", "seventeen", "eighteen", "ninteen"};

char *place[] = {"", "hundred", "thouands", "million", "billion", "trillion"};


int main(int argc, char **argv)
{
    int number, conv_num, places;
    places = 1;
    char *string = new char[1000];
    char *temp_string = new char[100];
    cout << "Enter a number:";
    cin >> number;
    string = " ";
    if (number >= 1000)
    {
        while(number >= 1)
        {
            conv_num = number % 1000;
            cout << "main 1:numbers are:" << conv_num << endl;
            temp_string = convert_number(conv_num);
            string =strcat(string, temp_string);
            string =strcat(string, " ");
            number = 0; // (number-conv_num)/1000;
            cout << "main 2:numbers are:" << endl;
            //cout << conv_num << ":" << number << endl;
        }
    }
    else
    {
        string = convert_number(number);
        string = strcat(string, " ");
    }
    cout<<"Main: The word is :"<<string<<endl;
}

char *convert_number(int number)
{
    int divisor;
    char *word;
    word = new char[100];
    divisor = 10;
    cout << "Function1: Number is " << number << endl;

    if (number >= 100)
    {
        word = strcat(word, words[number/100]);
        cout << word << endl;
        word = strcat(word, " hundred ");
        cout << word << endl;
        number = number%100;
        cout << number;
    }
    cout << "Function2: Number is " << number << endl;

    if (number >= 20)
    {
        word = strcat(word, tens[number/10]);
        word = strcat(word, " ");
        if (number%divisor >= 1)
        {
            word=strcat(word, words[number%divisor]);
            word =strcat(word, " ");
        }
    }
    cout << "Function3: Number is " << number << endl;

    if (number < 20)
    {
        word = strcat(word, words[number]);
        word = strcat(word, " ");
    }
    cout << "Returning word:" << word;
    return word;
}

Answer 1

你得到总线错误的原因是因为你正试图写入不可写区域(即写入字符常量，也超过它的末尾)；这是未定义的行为。

// Good: allocate 100 bytes to string 
char *string = new char[100];

// Bad! Compiler warns you that assigning character const to char* is wrong.
// It does not tell you that you've just leaked the 100 bytes that you allocated
/// before, but that's also true.
string=" ";

// ... some more code, and then
string = strcat(string,temp_string); // <<== HERE is the problem!

对 strcat 的调用尝试写入 string 的终止零，然后继续写入超过字符串常量的末尾。这是未定义的行为，因此您的程序会崩溃。

要解决此问题，您需要将"" 复制到string 中，而不是将其分配给string 指针。