Comment author: junsli

So which one do you propose: stderr should not be buffered?

stderr is not buffered on Linux. stdout is buffered until it finds '\n'.

Regarding OCaml, The manual does not mention its stderr is buffered, but it does mention that prerr_endline and prerr_newline flush the buffer. So I would take it as a design choice that ocaml buffers string (even string with \n) in stderr and provides two functions for you to flush the buffer.

Comment author: sbleazard

In general I think there is an expectation among programmers that an output named stderr is unbuffered. I think this is reasonable given the use cases for stderr.

Also, the buffered nature of stderr is bubbling up to the other library functions including Jane Street's eprintf. As a result I have to force a flush on every write when using stderr for the commonest use cases.

Based on this I would make stderr unbuffered in the same way as c, c++ and python

Comment author: @damiendoligez

Sounds reasonable.