perl reports fastcwd 'redefined' when using Cwd and -W

argv has asked for the wisdom of the Perl Monks concerning the following question:

Consider the following program:

#!/usr/bin/perl -W
use Cwd;
print "You're in '", getcwd(), "'\n";
[download]

I just moved up to the latest Redhat distribution, and perl is now generating the following error when I run this program:

Subroutine Cwd::fastcwd redefined at /usr/lib/perl5/5.8.5/i386-linux-thread-multi/XSLoader.pm line 92.

What happened? This is a virgin Redhat distribution, so I wouldn't expect this kind of error out of the box. Where's the problem? In Cwd? Or in XSLoader.pm?

Perl never used to generate this error. And, as you might expect, if I change -W to -w, the error goes away. How can I continue to use -W in my script and still keep perl quiet about this redefined routine. It does NOT go away if I merely precede the "use Cwd" with "no warnings 'redefine'" (though it seems it should). So, the question is, where is the real error, and what should I be doing?

PS: I did a Google search on this error message, and everyone else that's reported the same error seems to be on a windows box, and it was deemed the version of perl they were using was the culprit.

Dan Heller
http://www.danheller.com

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Re: perl reports fastcwd 'redefined' when using Cwd and -W by ikegami (Patriarch) on Jan 20, 2007 at 03:55 UTC
Cwd has various implementation of the same function for different OSs. It redefines some functions intentionally in order to optimize operations on OSs where certain paradigms are supported. It attempts to disable warnings if they are enabled, but `-W` (as opposed to `-w`) forces the warnings to remain on. From Cwd: `local $^W = 0; # assignments trigger 'subroutine redefined' warning *{$name} = \&{$map->{$name}};` [download]	[reply] [d/l] [select]
Re: perl reports fastcwd 'redefined' when using Cwd and -W by Anonymous Monk on Jan 20, 2007 at 00:44 UTC
Why do you have -W? -W Enables all warnings regardless of "no warnings" or $^W. See perllexwarn.	[reply]
Re^2: perl reports fastcwd 'redefined' when using Cwd and -W by argv (Pilgrim) on Jan 20, 2007 at 00:58 UTC
> Why do you have -W? Because this was an old script, written at a time when I apparently swapped my interpretation of -w and -W. I have since used -w in all my scripts, but forgot to see it in this case. thanks for pointing it out. In any event, it does seem that upgrading perl is the thing to do. I'm surprised that the "latest" version of Redhat doesn't have the most up-to-date version. Dan Heller http://www.danheller.com	[reply]
Re: perl reports fastcwd 'redefined' when using Cwd and -W by almut (Canon) on Jan 19, 2007 at 21:14 UTC
On Linux, it also seems to depend on the Perl version. Just tried it: with v5.8.4, I can reproduce the error, but not with v5.8.8. So, if upgrading is an option, that's probably the easiest route... Update: `no warnings 'redefine'`, as mentioned below, doesn't seem to help - i.e. I do get the same error with v5.8.4	[reply] [d/l]
Re^2: perl reports fastcwd 'redefined' when using Cwd and -W by Khen1950fx (Canon) on Jan 19, 2007 at 21:29 UTC
I ran it on FC6. It worked fine. You might try this: `#!/usr/bin/perl use Cwd; use strict; use warnings; no warnings 'redefine'; my $cwd = getcwd(); print "You're in '", getcwd(), "'\n";` [download]	[reply] [d/l]
Re^3: perl reports fastcwd 'redefined' when using Cwd and -W by ikegami (Patriarch) on Jan 20, 2007 at 03:48 UTC
That won't work for two reasons. `no warnings 'redefine';` won't affect Cwd, just the block in which it appears. It's lexically scoped. The `-W` used by the OP overrides `no warnings`.	[reply] [d/l] [select]