c++ - 简单的 char* 内存分配不起作用

Question

我有最简单的课文:

class Text
{
    char* txt;
public:
    Text(const char*);
    Text(const Text&);
    ~Text();

    const Text operator+(const Text&) const;
};

和实现:

#include "text.h"

Text::~Text()
{
    delete[] this->txt;
}


Text::Text(const char* argText)
{
    txt = new char[strlen(argText)+1];
    strcpy(txt, argText);
}

Text::Text(const Text& other)
{
    txt = new char[strlen(other.txt)+1];
    strcpy(txt, other.txt);
}

const Text Text::operator+(const Text& other) const
{
    char* ttxt, *newLine;
    ttxt = new char[strlen(txt)+strlen(other.txt)+2];
    strcat(ttxt, this->txt);
    newLine = new char[2];
    newLine[0] = '\n';
    newLine[1] = '\0';
    strcat(ttxt, newLine);
    strcat(ttxt, other.txt);
    Text temp(ttxt);
    delete[] newLine;
    return temp;
}

和主要:

#include "text.h"

int main()
{
    Text a("First text.");
    Text b("Second lol!!\n kthxbye!!!!!!!");
    Text c(a+b);
}

并且程序在 newLine = new char[2]; 处中断 我尝试增加它，就像 new char[5] 但它仍然中断。我收到的消息是:

Windows has triggered a breakpoint in prTextClass.exe.

This may be due to a corruption of the heap, which indicates a bug in prTextClass.exe or any of the DLLs it has loaded...

Answer 1

const Text Text::operator+(const Text& other) const
{
    char* ttxt, *newLine;
    ttxt = new char[strlen(txt)+strlen(other.txt)+2];
    strcat(ttxt, this->txt);
 // ^^^^^^^^^^^^^^^^^^^^^^^^ This line is buggy
    newLine = new char[2];
    newLine[0] = '\n';
    newLine[1] = '\0';
    strcat(ttxt, newLine);
    strcat(ttxt, other.txt);
    Text temp(ttxt);
    // ....

请注意，ttxt = new char[strlen(txt)+strlen(other.txt)+2]; 不会初始化数组内容。因此，当 strcat() 被调用时，它通过 ttx 找到第一个 '\0' 字符作为字符串 ttxt 并因此停在了一个未知的位置。

你应该把它改成

strcpy(ttxt, this->txt);