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Re: cin - Why Does It Require 2 Returns?

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On Tue, 23 Aug 2011 07:01:04 +0000, Juha Nieminen wrote:

>   I don't think one should rely on the output of std::cout for debugging
> purposes anyways. If adding debug prints, std::cerr should be used instead
> of std::cout. std::cerr will flush after each *character* (ok, I don't know
> if that's by standard, but at least the last time I checked with gcc it
> does). This is of course horribly slow, but good for debugging.

I'm not entirely sure how cout/cerr relate to stdout/stderr; however:

ISO C requires that initially stderr is not fully buffered while stdout is
fully buffered if and only if it can be determined not to refer to an
interactive device.

POSIX says the same thing, but the conventional Unix behaviour is that
initially stderr is unbuffered, while stdout is line buffered if it refers
to a tty and fully buffered otherwise.

Note that "unbuffered" doesn't actually mean the same thing as
"flush after each character"; the latter implies a write() per
byte. Ultimately, "unbuffered" just means the stream doesn't have a
persistent user-space buffer associated with it, so there's no way for a
write operation on a stream to be deferred past the point that the
function returns.

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cin - Why Does It Require 2 Returns? mrc2323@cox.net (Mike Copeland) - 2011-08-20 20:49 -0700
  Re: cin - Why Does It Require 2 Returns? Geoff <geoff@invalid.invalid> - 2011-08-20 21:12 -0700
    Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-21 17:21 +1200
  Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-21 17:20 +1200
    Re: cin - Why Does It Require 2 Returns? Eugén Jung <contact@eugenjung.tk> - 2011-08-21 23:19 +0100
      Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-22 11:38 +1200
        Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-23 07:34 +1200
          Re: cin - Why Does It Require 2 Returns? Victor Bazarov <v.bazarov@comcast.invalid> - 2011-08-22 15:54 -0400
          Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-23 08:02 +1200
            Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-23 08:39 +1200
              Re: cin - Why Does It Require 2 Returns? Ian Collins <ian-news@hotmail.com> - 2011-08-23 08:57 +1200
                Re: cin - Why Does It Require 2 Returns? Paul <pchristor@yahoo.co.uk> - 2011-08-23 02:47 -0700
              Re: cin - Why Does It Require 2 Returns? James Kanze <james.kanze@gmail.com> - 2011-08-26 08:07 -0700
        Re: cin - Why Does It Require 2 Returns? James Kanze <james.kanze@gmail.com> - 2011-08-26 08:00 -0700
    Re: cin - Why Does It Require 2 Returns? Juha Nieminen <nospam@thanks.invalid> - 2011-08-22 06:13 +0000
      Re: cin - Why Does It Require 2 Returns? James Kanze <james.kanze@gmail.com> - 2011-08-22 10:49 -0700
        Re: cin - Why Does It Require 2 Returns? Juha Nieminen <nospam@thanks.invalid> - 2011-08-23 07:01 +0000
          Re: cin - Why Does It Require 2 Returns? Nobody <nobody@nowhere.com> - 2011-08-24 07:11 +0100
          Re: cin - Why Does It Require 2 Returns? James Kanze <james.kanze@gmail.com> - 2011-08-26 08:12 -0700

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