From: Christopher Faylor <cgf-use-the-mailinglist-please@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Who's using "CYGWIN=tty" and why?
Date: Wed, 11 May 2011 15:40:00 -0000 [thread overview]
Message-ID: <20110511154025.GC19557@ednor.casa.cgf.cx> (raw)
In-Reply-To: <4DCAA510.9000909@sidefx.com>
On Wed, May 11, 2011 at 11:02:40AM -0400, Edward Lam wrote:
>On 5/11/2011 2:34 AM, Corinna Vinschen wrote:
>> Kind of weird. The difference is that in tty mode the stdio handles are
>> pipes, while in the notty case the stdio handles are console handles.
>> Usually native Windows applications shouldn't see a difference and even
>> work *better* in notty mode.
>
>One problem I ran into was with *Windows mode* applications (ie. MS
>link.exe option /SUBSYSTEM:windows) trying to detect stdout redirection.
>I apologize that this takes a bit of explaining first as to why we run
>into a problem with Cygwin.
>
>For Windows-mode applications, _isatty(_fileno(stdout)) will always
>return false. Due to a bug (in Windows and/or the CRT), the FILE *stdout
>object will be initialized to a black hole. So if you want printf's to
>make its way into the redirected file, you have to manually connect the
>FILE *stdout object to the redirected file output handle.
>
>The usual method is to call GetStartupInfo(&info) and check if
>info.dwFlags has the STARTF_USESTDHANDLES flag set. If it is set, then
>assume that info.hStdOutput contains the redirected file output handle
>and attach it with something like:
> *stdout = _fdopen(_open_osfhandle(info.hStdOutput, _O_TEXT));
>
>So this brings us to Cygwin. When we spawn such a Windows mode app from
>Cygwin, the method I describe above fails. The call to
>_open_osfhandle(info.hStdOutput, _O_TEXT) returns with an error value of
>-1. This is likely why jam reports "the handle is invalid".
>
>Personally, when I first ran into this problem, I never realized that
>CYGWIN=tty would fix it. I did notice that there was a change in the
>behavior between Cygwin B20 and the Cygwin 1.X releases but I only
>realize now that this was probably the reason.
Just to go on mean record: I don't think the fact that jam works better
as side effect of setting CYGWIN=tty is a good enough reason to derail
any plans to get rid of CYGWIN=tty.
It seems like you might be able to get the same behavior by saying
jam </dev/null 2>&1 | cat
cgf
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next prev parent reply other threads:[~2011-05-11 15:40 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-10 21:18 Len Giambrone
2011-05-11 6:35 ` Corinna Vinschen
2011-05-11 10:12 ` David Antliff
2011-05-11 15:02 ` Edward Lam
2011-05-11 15:40 ` Christopher Faylor [this message]
2011-05-11 16:00 ` Edward Lam
2011-05-11 16:00 ` Andy Koppe
-- strict thread matches above, loose matches on Subject: below --
2011-05-09 16:11 Corinna Vinschen
2011-05-09 16:21 ` Henry S. Thompson
2011-05-09 16:34 ` Corinna Vinschen
2011-05-09 17:37 ` Henry S. Thompson
2011-05-10 8:56 ` Corinna Vinschen
2011-05-10 1:42 ` rifter rifter
2011-05-09 16:32 ` Andrew Schulman
2011-05-09 16:40 ` Edward Lam
2011-05-09 17:03 ` Ken Brown
2011-05-09 20:00 ` Christopher Faylor
2011-05-09 20:06 ` Christopher Faylor
2011-05-09 17:41 ` Lee Maschmeyer
2011-05-09 17:52 ` Samuel Thibault
2011-05-09 20:05 ` Christopher Faylor
2011-05-09 20:23 ` Samuel Thibault
2011-05-10 14:09 ` Corinna Vinschen
2011-05-10 14:59 ` Andy Koppe
2011-05-10 13:39 ` Lee Maschmeyer
2011-05-10 15:36 ` Charles Wilson
2011-05-10 16:45 ` Lee Maschmeyer
2011-05-09 21:14 ` Karl M
2011-05-09 21:39 ` Jeremy Bopp
2011-05-09 22:27 ` Thomas Wolff
2011-05-09 23:18 ` Christopher Faylor
2011-05-10 2:30 ` Claude Sylvain
2011-05-10 8:29 ` Csaba Raduly
2011-05-10 9:02 ` Corinna Vinschen
2011-05-10 13:38 ` Buchbinder, Barry (NIH/NIAID) [E]
2011-05-10 17:19 ` Christopher Faylor
2011-05-10 17:50 ` Christopher Faylor
2011-05-10 22:12 ` Buchbinder, Barry (NIH/NIAID) [E]
2011-05-10 22:17 ` Christopher Faylor
2011-05-10 14:51 ` Bernhard Ege
2011-05-10 14:58 ` Jeremy Bopp
2011-06-08 19:30 ` Christopher Faylor
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