c++ - 在没有指向任何文件名的情况下使用 ofstream 时 << 发生了什么？

Question

(1) default constructor
Constructs an ofstream object that is not associated with any file.
Internally, its ostream base constructor is passed a pointer to a newly constructed filebuf object (the internal file stream buffer).

在没有指定任何文件名的情况下使用 ofstream 时 << 发生了什么？

ofstream  ofstream;
ofstream<<1<<endl;

“1”去哪儿了？有什么问题吗？我试过了，没问题。但我找不到任何代码线索，任何人都可以显示内部代码解释吗？

Answer 1

没有任何反应。

[C++11: 27.9.1.1/3]: In particular:

• If the file is not open for reading the input sequence cannot be read.
• If the file is not open for writing the output sequence cannot be written.
• A joint file position is maintained for both the input sequence and the output sequence

关闭流，设置错误标志并忽略数据。

例子:

#include <iostream>
#include <fstream>

int main()
{
    std::ofstream ofs;
    ofs << 1 << std::endl;

    std::cout << ofs.good() << std::endl;
}

// Output: 0

Live demo