Re^2: Unexpected warning

[LanX]

> You get that warning on that line if $something is undefined.

yep I can reproduce this. =)

Seems like in the context of the call warnings were disabled.

  DB<132> use warnings; sub tst {my $a=shift, my $b =shift}

  DB<133> %h=()

  DB<134> $bla=""
 => ""

  DB<135> tst $h{$bla}
 => (undef, undef)

  DB<136> undef $bla
 => undef

  DB<137> tst $h{$bla}
Use of uninitialized value in scalar assignment at (eval 81)[multi_per
+l5db.pl:644] line 2.

[salva]

I can reproduce it myself too now:

tst(undef);        # doesn't warn from tst
tst($foo{undef});  # doesn't warn from tst
tst($foo{$undef}); # warns from tst

I would say this is a bug in perl, or I am missing something?

[samwyse]

The undef value is subtly different from using an undefined variable, so that may be causing the problem.

tst($foo{undef});  # doesn't warn from tst

This uses the undef value as a key into the %foo hash; the key presumably doesn't exist so Perl returns undef. This is working as I would expect.

tst($foo{$undef});  # warns from tst

This looks up the value of $undef, which presumably isn't defined, so Perl should flag an error at that statement, not inside tst. If that is the case, then it, too, is working as I would expect.

[hdb]

I get no warnings from the code below:

use strict;
use warnings;
sub test { my $x = shift; }
my %hash = ( a => "a" );
test $hash{"b"};

[LanX]

The key must be undef.

lanx@nc10-ubuntu:~$ perl
use strict;
{ use warnings;
  sub test { my $x = shift; }
}
my %hash = ( a => "a" );
my $key;
test $hash{$key}
Use of uninitialized value in scalar assignment at - line 3.

lanx@nc10-ubuntu:~$ perl -version

This is perl, v5.10.0 built for i486-linux-gnu-thread-multi

I agree with salva that this is kind of a bug in lexical warnings.