fstat st_size on open files on Parallels filesystem is wrong

Andrey Repin anrdaemon@yandex.ru
Mon Apr 21 18:35:00 GMT 2014


Greetings, lennox@cs.columbia.edu!

> I’m running cygwin64 1.7.29 in a Windows 8.1 Pro virtual machine, running in
> Parallels Desktop 9.0.24229 on Mac OS X 10.9.2.

> Parallels Desktop automatically mounts my Mac OS X home directory as a Z:
> drive in Windows.  Cygwin mount reports this drive as being type "prlsf".

> Unfortunately, I've discovered that if I have an open file on this
> filesystem which has been written to, the size returned by Cygwin fstat() on
> the open file is wrong.  A stat() of the file after it's been closed is
> correct.

> This has the consequence that emacs always thinks saved files have been
> modified externally, since emacs looks at files' sizes (as well as their
> modification times) to detect external changes.  This makes emacs
> near-unusable.

> This problem does not occur for files in my Cygwin home directory, or other
> locations mounted on my Windows C: drive.

> I've attached a simple unit test program that illustrates the problem.
> I've also attached my cygcheck -s -v -r output.

> Any ideas?  Is this a Cygwin bug, a Parallels bug, or something else?
> Glancing over the Cygwin code, I see that there are a few cases where fstat
> has special cases for certain filesystem types.

You never flushing the buffer in your test code, or I'm reading it wrong?


--
WBR,
Andrey Repin (anrdaemon@yandex.ru) 21.04.2014, <22:33>

Sorry for my terrible english...


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