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RE: From Microsoft: Windows 10 Console and Cygwin

Thanks Corinna.

The info I sent on the bug below is all that I have. It's quite likely related to the stability of the version of Win 10 it was run against. My larger purpose is to reach out to you all and see what we can do to help Cygwin run with our new console, we don't want to break anybody if at all possible. Please send me the info on the Windows 7 issue and I'll review and get back to you about whether we are able to help. If we "can" (figure it out, understand and repro the issue, not several weeks worth of work) we'll get to it.


-----Original Message-----
From: Corinna Vinschen [] 
Sent: Wednesday, April 29, 2015 1:06 PM
To:; Rich Eizenhoefer
Subject: Re: From Microsoft: Windows 10 Console and Cygwin

Hi Rich,

nice to read from you.

On Apr 29 19:01, Rich Eizenhoefer wrote:
> Hi,
> I'm the Program Manager at Microsoft for the updated Windows 10 
> console. I searched the Cygwin FAQ and mailing list archives for 
> issues related to Windows 10 and found an item about multiple windows 
> which should already be fixed. We have received a couple reports about 
> crashes when running on Windows 10 with the new console enabled. For
> example:
> "cygwin is dying when i run a bunch of the git tools. For example: >grep -rin log .\ 0 [main] us 0 init_cheap: VirtualAlloc pointer is null, Win32 error 487 AllocationBase 0x0, BaseAddress 0x68570000, RegionSize 0x3A0000, State 0x10000 C:\Program Files (x86)\Git\bin\grep.exe: *** Couldn't reserve space for cygwin's heap, Win32 error 0"

This error message is a bit weird.  For one thing, it would be nice if you could give us a pointer to the message.  I'm not aware of such a bug report.

Also, this is about a non-Cygwin version of git as the path to the git tools suggests.  On the other hand, if it's not a Cygwin version, the error message itself only makes marginal sense.  So maybe it's a Cygwin DLL as part of some third party package which is often outdated in relation to the official Cygwin distro version.

As for the error message itself, it refers to the fact that, after a Cygwin fork() call, the forked child can't reserve the space required for the so-called "cygwin heap", a region used for internal usage especially important for fork/exec related stuff.  This usually points to Cygwin DLLs which are not rebased, or a non-Cygwin DLL loaded into a spot required for a Cygwin DLL after a fork.  This is especially a problem on 32 bit due to the restricted virtual memory.

However, if I'm not completely off-track, the bug report does not really have anything to do with a bad interaction between the W10 console and Cygwin.  While my own W10 virtual machine under Qemu/KVM fails to update to versions after build 9926, I didn't encounter any unusual behaviour of the W10 console in comparison with, say, the W8.1 console yet.  I'm usually running Cygwin tools in mintty, but I did test the W10 console, too, of course.

> Please let me know if there are other problems you are experiencing 
> with the W10 console that are a regression from previous versions. We 
> are a small team, but we want to help where possible to ensure that 
> Cygwin continues to run well in Windows 10.

Thanks for the offer.  We have a regression introduced with Windows 7 and never fixed in W8 or 8.1, albeit I reported it as part of the Windows 7 beta tests.  Are you interested to give this a whirl as well?


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

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