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Subject:	Confusion with ACLs and Perl's file tests...maybe bug???
From:	Marco Moreno <mmoreno AT pobox DOT com>
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Date:	Mon, 5 Dec 2011 16:17:52 -0500
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[Oops, trying again with fixed formatting (dratted gmail!)]

Forgive me if this is not a cygwin specific issue.  I have a problem I don't know
how to solve that involves ACLs on a remote server (via UNC) and Perl's file tests.

The following may best describe my problem:

   $ cd //webdev/e/Temp

   $ ls -l
   total 1
   -rwx------+ 1 Administrators Domain Users 14 Dec  5 12:55 foo.txt

   $ getfacl foo.txt
   # file: foo.txt
   # owner: Administrators
   # group: Domain Users
   user::rwx
   group::---
   group:SYSTEM:rwx
   group:Users:r-x
   mask:rwx
   other:---

   $ groups
   Domain Users Users

   $ cat foo.txt
   Hello world!

Bash sees the file as readable:

    $ [[ -r foo.txt ]] && echo "readable"
    readable

But Perl does not due to ACLs:

    $ perl -e 'print "readable\n" if -r "foo.txt"'

Workaround is to use "filetest" pragma:

    $ perl -e 'use filetest "access"; print "readable\n" if -r "foo.txt"'
    readable

But now use of stat()'s _ cache fails as documented in 'perldoc filetest':

    $ perl -e 'use filetest "access"; print "writable\n" if -w "foo.txt"; print "readable\n" if -r _'

Simple answer is "just don't do that", but what about modules?

    $ perl -e 'use Archive::Zip; $z = Archive::Zip->new(); $z->add_file("foo.txt")'
    Can't locate object method "add_file" via package "Archive::Zip::Archive" at -e line 1.

    $ perl -e 'use filetest "access"; use Archive::Zip; $z = Archive::Zip->new(); $z->add_file("foo.txt")'
    Can't locate object method "add_file" via package "Archive::Zip::Archive" at -e line 1.

Constructor in Archive::Zip::NewFileMember::_newFromFileNamed() fails due to:

    return undef unless ( stat($fileName) && -r _ && !-d _ );

So Archive::Zip is currently unusable, with or without 'use filetest'.

Now all this seems to me to be a bug in Perl.  The file test flags should not care
what filesystem is in use and/or whether 'use filetest' is in effect.  Seems to me
like the filetest pragma is an ugly hack that should never have been implemented.

In other words, -r (et al.) should return true if the file is
readable.  Period.

Am I wrong here?  Or missing something?

Having said that, I know Cygwin has hacked Perl in many places to "do the right thing".
Is this another case?  Or is this not Cygwin's problem to solve?  What is the best way
to address this?

Regards,

Marco Moreno


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