Re: A small game
On Sep 18, 3:37 pm, Juha Nieminen <nos...@thanks.invalid> wrote:
James Kanze wrote:
There is no "line oriented" (I think you mean line buffered)
output in C++. std::cerr is "unit buffered", which means that
output is flushed after each operation (each << operator).
Actually I remember I tested this once, and at least with gcc
std::cerr flushes after each written *character*.
Which certainly isn't forbidden. As I mentionned, Sun CC seeks
before and flushes after every << operator.
I'm not sure when "unitbuf" was introduced. I don't remember it
from the classical iostream, but that could very easily be
simply because I never used it. (It is present if I include
<iostream.h> and compile with compat=4 with Sun CC, which is as
close to classical iostream as I can come today.) There is, at
any rate, some tradition for having standard error unbuffered,
although the C standard only requires it to not be fully
buffered, and the C++ standard that the unitbuf attribute be set
(but it can still have a buffer size of 0, if that's what the
implmentation wants to do).
I might add that the standard streams are synchronized with
stdio by default. This means that the cout must be flushed
before any output to stdout; since in most implementations, the
C library is separate and doesn't "know" of the existance of the
C++ library, this means that 1) all of the standard streams must
be unit buffered, and 2) that every output must start with a
fflush( NULL ). (In fact, I'm not sure how it's even
implementable for input, unless the implementation uses a
special streambuf which actually uses stdin to do the input.)
(I have to admit, though, that this was a long time ago and I
haven't tested this recently, and I don't know if it has been
changed. In a way it doesn't makes sense, because if you are
outputting eg. the value of an integer variable which has
several digits, and the program is forcefully terminated in
the middle of printing that value, the output will have the
first digits of the number but not the last ones, which can
make the output misleading and confusing.)
Sort of. It's text output, and generally, with text, you should
not count on anything in an incomplete last line.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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