Advice for debugging heap mismatches? (Win10 Insider build 14926)

Mark Geisert
Mon Oct 3 06:57:00 GMT 2016

Tony Kelman wrote:
>> You've got two different cygwin1.dll somewhere on your PATH.
> For more information, I have one cygwin64 installation on C:, one
> cygwin32 installation on E:, and they're never both on my path at
> the same time. I'm not sure where that orphan registry entry that was
> showing up in cygcheck.out came from, but I removed it and it made no
> difference.

With only one Cygwin installation on C: I can only come up with wild guesses. 
Are you somehow alternating between the C: and E: Cygwin versions, or running 
them simultaneously from separate windows, or accidentally running 32-bit Cygwin 
commands from a 64-bit Cygwin terminal window?  Unusual stuff like that?

One sure-fire way to make sure your 32-bit E: installation is not causing havoc 
with your 64-bit C: installation is to temporarily rename E:\cygwin32 to 
E:\somethingelse and retry your build.  This should not be necessary but I don't 
know what else to suggest.

I have in the past run 32-bit and 64-bit Cygwin installations simultaneously on 
the same machine, in order to build 32-bit and 64-bit Cygwin DLLs at the same 
time.  Never had a problem.  But that was Windows 7 so probably not applicable.

> This is absolutely due to a change in Windows itself. 3 updates in
> a row now, 14926, 14931, and now 14936, it's 100% reproducible just
> from updating Windows. Downgrading to build 14915 gets everything back
> working again, but that build is now expired so the only way for me to
> get back to a supported build of Windows where cygwin works properly
> is by totally reinstalling Windows. I haven't done that yet, but if
> we can't identify the problem and a solution soon, I will have to.

I see what you've been saying about different insider builds of Windows 10 but I 
don't think anybody here is beating up on these releases.


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