Re: [PATCH] Unbuffer stdout and stderr on windows

[Yao Qi <yao@codesourcery.com>]

On 07/22/2013 11:40 PM, Eli Zaretskii wrote:
> This is wrong, stdout should be line-buffered by default.
>

stdout is line-buffered if it can be detected to connect to an 
interactive device, otherwise it is fully buffered.  Cygwin emulates pty 
with pipes, and native win32 apps blindly assume all pipes are 
non-interactive.

> Also, this punishes batch mode with stdout redirected to a file: its
> stdout buffering (and perhaps also that of stderr, although that's
> less important) will now always be line-buffered, i.e. less efficient.

Yeah, this patch hurts the performance, but gets the outputs in the 
correct order, so that testsuite can be run to get a reasonable test result.

>
> Is it possible to detect the "Cygwin ssh session", whatever that
> means, and only do this then?  I don't think it's right to change

Unfortunately, I am unable to find a heuristics to tell "GDB is in 
cygwin session".  There are some differences on env variables between 
cygwin and Windows cmd.exe console, but I am afraid that they are not 
reliable.

> behavior of a native w32 GDB just because it misbehaves when mixed

This patch is to change the buffered output to unbuffered, so the 
behaviour of GDB is not changed, IMO.

> with Cygwin.  Mixing native and Cygwin programs is asking for trouble
> to begin with, so punishing good citizens on behalf of that corner
> case is not TRT, IMO.

We test mingw native gdb in cygwin, because it is easy to set up, so 
that mingw32 native gdb can be tested more widely.  In the last resort, 
we may add an option "--cygwin-tty", which I don't really like.

-- 
Yao (齐尧)