c++ - 分配动态内存以存储字符串拷贝时程序中断

Question

我想看看我的所有功能是否正常工作，程序运行到黑屏并关闭，它给我一个错误，三角形内有黄色三角形感叹号，表示

“在 milestone2.exe 0xC0000005 中抛出异常 0x01971FD0 (ucrtbased.dll):访问冲突读取位置 0x0000000”

指示 .cpp 文件的箭头 m_message = new char [strlen(str) + 1 ] 位于 void ErrorMessage::message(const char* str) at

我猜这是某种内存问题，有人知道解决方案吗？

头文件

#ifndef SICT_ERROR_H_
#define SICT_ERROR_H_
namespace sict {
    class ErrorMessage {
        char* m_message;
    public:

        ErrorMessage(const char* errorMessage = nullptr);
        ErrorMessage(const ErrorMessage& em) = delete;
        ErrorMessage& operator=(const ErrorMessage& em) = delete;
        virtual ~ErrorMessage();
        void clear();
        bool isClear() const;
        void message(const char* str);
        const char* message() const;
    };
    std::ostream& operator<<(std::ostream& ostr, ErrorMessage);
}
#endif

Cpp文件

#include "ErrorMessage.h"
#include <iostream>
namespace sict {

    ErrorMessage::ErrorMessage(const char* errorMessage) {
        m_message = nullptr;
        message(errorMessage);
    }
    void ErrorMessage::clear() {
        delete[] m_message;
        m_message = nullptr;
    }
    void ErrorMessage::message(const char* str) {
        delete[] m_message;
        m_message = new char[strlen(str) + 1];
        strcpy(m_message, str);
    }
    const char* ErrorMessage::message() const {
        return m_message;
    }
    ErrorMessage::~ErrorMessage() {
        clear();
    }
    bool ErrorMessage::isClear() const {
        if (m_message == nullptr) {
            return true;
        }
        return false;
    }
    std::ostream& operator<<(std::ostream& ostr, ErrorMessage error) {
        if (!(error.isClear())) {
            ostr << error.message();
        }
        return ostr;
    }


}

main.cpp

#include <iostream>
#include "ErrorMessage.h"

using namespace std;
using namespace sict;

int main() {
    ErrorMessage T("Testing Error Message Module");
    ErrorMessage e;
    int ret = 0;
    bool ok = true;
    cout << T << endl << e << endl << "isClear(): " << (e.isClear() ? "Passed!" : "Failed!") << endl;
    if (!e.isClear()) ok = false;
    cout << endl;
    cout << "===========| Long Message\r";
    for (int i = 0; i < 10000000; i++) {
        if (i % 1000000 == 0) {
            cout << "*";
            cout.flush();
        }
        e.message("Some error message that is really long long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long"
            " long  long  long  long  long  long  long  long  long  long  long  long  long");
    }
    cout << '*' << endl;
    cout << e << endl << "isClear(): " << (e.isClear() ? "Failed!" : "Passed!") << endl;
    if (e.isClear()) ok = false;
    cout << endl;

    e.message("Short Message");
    cout << e << endl << e.message() << endl << "isClear(): " << (e.isClear() ? "Failed!" : "Passed!") << endl;
    if (e.isClear()) ok = false;

    e.clear();
    cout << e << endl << "isClear(): " << (e.isClear() ? "Passed!" : "Failed!") << endl;
    if (!e.isClear()) ok = false;
    cout << endl;

    if (ok) {
        cout << "You passed all the tests!" << endl;
    }
    else {
        cout << "You did not pass all the tests" << endl;
        ret = 1;
    }

    return ret;
}

Answer 1

在你的 main() 中你有:

ErrorMessage e;

它将使用空指针调用您的构造函数:

ErrorMessage::ErrorMessage(const char* errorMessage) {
    m_message = nullptr;
    message(errorMessage);
}

然后您的构造函数将调用 message() 并将该空指针传递给它:

void ErrorMessage::message(const char* str) {
    delete[] m_message;
    m_message = new char[strlen(str) + 1];
    strcpy(m_message, str);
}

因此，您正在尝试对空指针执行 strlen()。这就是它给出段错误的原因。