奇怪的文件输出 C++

Question

我想打印数字并在它们之间放置一个空格，但在编译之后我注意到我将 + 运算符留在了那里（C# 练习）。当我运行这个程序时，它立即停止工作，但文本文件中有一个非常奇怪的输出。为什么文本文件是这样的？

#include <iostream>
#include <fstream>
using namespace std;

    int main()
    {
        int i=0;
        ofstream f("out.txt");
        while(i != -1)
        {
            f << " " + i++;
        }
        return 0;
    }

551Kb 文件中的一些行：

deleted virtual method called
eleted virtual method called
leted virtual method called
eted virtual method called
ted virtual method called
ed virtual method called
d virtual method called
 virtual method called
virtual method called
irtual method called
rtual method called
tual method called
ual method called
al method called
l method called
 method called
method called
ethod called
thod called
hod called
od called
d called
 called
called
alled
lled
led
ed
d

Answer 1

当您将整数添加到字符串文字时，它会执行指针运算。所以" " + i++ 获取字符串文字的地址，将i 添加到它，并增加i。然后它将加法的结果传递给<<，因此该地址处的任何 C 样式字符串都会打印到文件中。

由于您在字符串文字的内存范围之外访问，这会导致未定义的行为。所以它正在将垃圾写入文件。看起来您的字符串文字后的内存包含来自运行时库的内部错误消息，并且您正在打印该字符串。由于i 每次都会递增，因此每次迭代都会在消息的后面开始一个字符。

您实际上还有一个无限循环，因为递增 i 不会导致 -1 溢出并回绕。