What is the C++ iostream endl fiasco?

Question

I was listening to a google talk by Andrei Alexandrescu on the D programming language when he threw out a one liner about the "endl" fiasco. I just thought endl was the preferred way to signify the end of a line and flush the buffer for a stream. Why is it considered a fiasco? Should I not be using it in my code?

Answer 1

Reposting from my comment:

(I assume) He just means that many, especially new, C++ programmers use std::endl blindly instead of '\n' for newline, flushing unnecessarily frequently and potentially making the performance of their program abysmal.

I.e., most people are taught that std::endl is the canonical way to insert a newline into a stream even though it is very rarely necessary or appropriate to flush it.

It is some people's opinion (*cough*) that std::endl shouldn't even be in the standard, as it is so rarely appropriate and not a significant typing savings over '\n' << std::flush anyway.

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TL;DR(s):

• In the end, std::endl buys you nothing except usually worse performance and usually more typing.
• It has its uses, but they are considerably rarer than its frequency of use in most large codebases would suggest, therefore...
• Its utility is highly questionable and its ubiquity is absurd – a fiasco indeed!