Re: Regression on XP with "Fix OPOST for non-Cygwin pty slaves"

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On May  1 16:25, Johannes Schindelin wrote:
> Hi Yano & Corinna,
> 
> I would like to ask you for help with fixing a regression I am experiencing
> on XP (and XP only, the problem does not occur with Windows 7 or 8). It may
> be a 32-bit issue, but I cannot currently test on 64-bit XP.
> 
> Background: I am the maintainer of Git for Windows and we are hoping to
> release a new major release Real Soon Now, based on MSys2 (which in turn is
> based on Cygwin). To make the user experience a bit better, we want to allow
> users to double-click a "Git Bash" icon that simply launches a small,
> non-console MinGW executable which in turn basically sets up the PATH and
> MSYSTEM environment variables (as required for the MSys2 runtime) and then
> launches a mintty with a bash inside. Please note that this small executable
> is *not* a console program but a GUI one (-mwindows instead of -mconsole) so
> that no console window flashes before the mintty window is shown.
> 
> Now, this strategy worked well so far, except that I recently found that Git
> Bash does not start in XP anymore, instead the mintty process just sits and
> waits for a while and after five to ten minutes, the mintty window appears
> with the message:
> 
>     Failed to fork child process: Resource temporarily unavailable.
>     DLL rebasing may be required. See 'rebaseall --help'.
> 
> (Needless to say, a 'rebaseall' does not fix it.)
> 
> This problem does *not* occur if I call mintty from a `.bat` file or from
> `cmd` -- but as I said, I want to avoid flashing console windows -- and it
> also does not happen if I run a mintty from a freshly installed Cygwin (with
> cygwin package version 2.0.1-1) where the shortcut points directly to
> `mintty` which is a console application.
> 
> This symptom makes me believe that the culprit might be that msys-2.0.dll
> somehow expected an attached Win32 Console, and spins in circles when there
> is none.
> 
> Now, please note that I do *not* run a regular cygwin1.dll but rather an
> msys-2.0.dll that I had to patch even more to support users of the previous
> Git for Windows version (which was based on MSys1 and did things like
> allowing users to override their home directory using the HOME environment
> variable).
> 
> Starting with the diff on top of cygwin1.dll's sources, I bisected the
> problem down to the commit "Fix OPOST for non-Cygwin pty slaves":
> 
> https://cygwin.com/git/gitweb.cgi?p=newlib-cygwin.git;a=commit;h=063e7da36fda3f42619d7df606d9f3d4920605aa
> 
> With this commit reverted, on top of the MSys2 and the Git for Windows
> patches, the mintty window appears correctly again when launched on 32-bit
> XP via said GUI executable. You can see my current state here:
> 
> https://github.com/git-for-windows/msys2-runtime/tree/aae52e6d23e92cf71e6f7777ff9bb49588be8fdc
> 
> I would like to ask you for advice how to debug this regression further
> because I really would like to revert the revert and have a proper fix. Or
> maybe you have an idea how I can fix it directly?

Hmm, this seems to be another fallout from introducing different OPOST
processing (via spearate pipes) for native and Cygwin processes.
Does the patch from https://cygwin.com/ml/cygwin/2015-05/msg00282.html
help, by any chance?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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