[PATCH] Unbuffer stdout and stderr on windows

[Eli Zaretskii]

> Date: Mon, 12 Aug 2013 14:11:05 -0700
> From: Joel Brobecker <brobecker@adacore.com>
> 
> > We had a somewhat heated debate in the cygwin list about using the
> > techniques in winpty and eventually abandoned the idea because the way
> > things like winpty create consoles is not foolproof.  Since it relies on
> > polling, it is theoretically possible to lose data.
> > 
> > I'll bet that, in practice you'd never see any data loss, though.
> > And, from that observation, you can see which side of the argument
> > I was on.  :-)
> 
> FWIW, many frontends also implements communication with GDB using
> pipes on Windows, and running MinGW-gdb inside cygwin window/shell
> is just a very very common practice, regardless of whether officially
> supported or not. How does Emacs do, for instance? IIRC when I looked
> at the code, that's what it did.

Yes, Emacs does that.  But it is never a problem in that case, because
it's the user who looks at the results, not a program that wants to
interpret them.

> Having the stdout/stderr output mixed up is very confusing and breaks
> testing as well, so we applied the same approach as Yao's at AdaCore.

Making GDB output unbuffered is not a good idea for Emacs, because it
will cause it read single characters, which is (a) inefficient, and
(b) error-prone, because a single CR character could dupe the text
decoding routines into thinking the EOL format is from Mac.

I think this problem is only relevant to the test suite, where a
program tries to interpret the output and trips on extraneous
characters.  Let's not make the solution so much wider than the
problem.  With Yao's patch, you now have this in a Cygwin terminal;
can we leave all the other types alone, please?