tar deletes .exe files on extraction (again)

Ryan Johnson ryan.johnson@cs.utoronto.ca
Fri Sep 23 19:07:00 GMT 2011


On 22/09/2011 9:56 PM, Larry Hall (Cygwin) wrote:
> On 9/22/2011 4:57 PM, Steve Atkins wrote:
>> In the process of trying to build Qt on Windows in a cygwin shell, I've
>> discovered that neither tar nor unzip will work reliably under Cygwin -
>> untaring an archive will not correctly create the files that the archive
>> contains. The "configure.exe" that's required to build Qt is never 
>> extracted
>> from the tarball.
>>
>> The problem is that the cygwin filesystem shims consider "configure" and
>> "configure.exe" to be almost the same, despite their having different
>> filenames, so when tar extracts an archive containing both it ends up
>> deleting the existing "configure.exe" when it creates "configure".
>>
>> This was discussed a couple of years ago -
>> http://cygwin.com/ml/cygwin/2009-08/msg00293.html - and the conclusion
>> seemed to be that cygwin was working as designed, and the user just
>> shouldn't ever be doing anything that requires both "foo" and "foo.exe"
>> under cygwin, and that if they do want to do that, they probably 
>> shouldn't
>> be using cygwin.
>>
>> That seems like a fairly nasty limitation / bug, and makes use of the
>> cygwin shell a bit too brittle to rely on for build automation - I'm
>> wondering if anyone knows if there's been any change in the situation 
>> since
>> then?
>
> No, no change and probably not likely to be anytime soon.  By using the
> Windows build environment for QT, you're trying to force a Windowsism 
> into
> Cygwin's POSIX environment.  The transparency of the ".exe" extension is
> already a concession to a Windowsism, namely that executables must have a
> .exe extension.  Cygwin needed to support this one though to make 
> allot of
> POSIX scripts work without alteration.  That may cause breakage in corner
> cases like the QT Windows build environment but that's the (far) 
> lesser of
> two evils.  Cygwin's striving to provide a POSIX environment in a Win32
> environment after all.  I know nothing about the QT build environment but
> from what you've said, it doesn't sound like it's assuming a POSIX
> environment for building on Windows.  I'd recommend sticking with tools
> that conform to the Windows requirements if you're building for Windows.
>
> That said, going forward, there may come a day when all Cygwin 
> executables
> no longer have the .exe extension, which was really an interoperability
> concession to Windows 9x/Me platforms.  Cygwin 1.7 doesn't support 
> 9x/Me, so the concession is now largely a historical one and could 
> possibly be
> changed.  But even if it were to happen, it would be a big undertaking 
> due
> to the number of Cygwin packages that would be affected (i.e. all).  It
> would take quite a while to trickle down to the majority of packages.  
> And
> only at that point might it make sense to remove the transparent handling
> of exe.  So that brings me back to my opening statement. :-)
Wild speculation here...

A quick test shows that ./a indeed works fine inside cygwin whether the 
'.exe' is present or not, though it would be a little challenging invoke 
such binaries directly from Windows.

So... how hard would it be to provide 
"CYGWIN=(no)disabletransparent_exe"?*** There could a very simple 
utility, similar to rebaseall, which strips the .exe extension from 
cygwin executables (identifiable from cygcheck or their presence in 
standard paths), and which accepts additional paths to clean up. People 
needing the functionality would be responsible run the utility properly 
(after installing new packages, don't mess with Windows paths, etc.).

That would require no changes to any package to give the desired 
behavior, and as packages change they would just fit right in (no .exe 
in the package ==> no fuss).

Of course, SHTDI...

Ryan

*** The old, removed "transparent_exe" has the wrong boolean sense to 
work the correct way by default

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