CODEWITHSUNDEEP
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Agrudge Amicus
Agrudge Amicus

Reputation: 1103

fstream object default association

In this program:

#include<iostream>
#include<fstream>

int main()
{
    std::ofstream ob;

    ob<<"hello"<<std::endl;
    return 0;
}

Where is this hello written/outputted since ob is not associated with any file? Is it the internal file buffer?

Upvotes: 1

Views: 47

Answers (2)

Spencer
Spencer

Reputation: 2214

The output is ignored.

When anything is written to a stream, it calls the overflow method (or an internal equivalent) of its associated streambuf for each character written. As per cppreference.com for std::basic_filebuf:

If the associated file is not open (is_open() == false), returns Traits::eof() before doing anything.

As soon as overflow returns an eof, the stream's failbit is set and all other output is ignored.

Upvotes: 2

Ron
Ron

Reputation: 15521

The std::ofstream class template has several constructors. This example uses the std::ofstream default constructor to construct an object that is not associated to a file.

Excerpt from the reference:

1) Default constructor: constructs a stream that is not associated with a file: default-constructs the std::basic_filebuf and constructs the base with the pointer to this default-constructed std::basic_filebuf member.

@Spencer's answer details what happens then.

Upvotes: 1

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