Perl CGI.PM: Use of uninitialized value $vals

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

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Re: Perl CGI.PM: Use of uninitialized value $vals by kcott (Archbishop) on Apr 30, 2018 at 08:52 UTC
It's generated by code something like these: `$ perl -wE 'my $vals; my $y = index($vals, "x")' Use of uninitialized value $vals in index at -e line 1. $ perl -wE 'my $vals; my $y = index("x", $vals)' Use of uninitialized value $vals in index at -e line 1.` [download] Look in `/homedir/perl5/lib/perl5/CGI.pm`, go to line `1243`, and start investigating from there. — Ken	[reply] [d/l] [select]
Re^2: Perl CGI.PM: Use of uninitialized value $vals by Anonymous Monk on Apr 30, 2018 at 09:09 UTC
I do not have code calling the method index, but rindex yes.	[reply]
Re^3: Perl CGI.PM: Use of uninitialized value $vals by poj (Abbot) on Apr 30, 2018 at 09:17 UTC
What version of CGI do you have ?. In 3.65 the code was `sub STORE { my $self = shift; my $tag = shift; my $vals = shift; my @vals = index($vals,"\0")!=-1 ? split("\0",$vals) : $vals; $self->param(-name=>$tag,-value=>\@vals); }` [download] In 4.37 it is `sub STORE { my $self = shift; my $tag = shift; my $vals = shift; my @vals = defined($vals) && index($vals,"\0")!=-1 ? split("\0",$v +als) : $vals; $self->param(-name=>$tag,-value=>\@vals); }` [download] poj	[reply] [d/l] [select]
Re^4: Perl CGI.PM: Use of uninitialized value $vals by Anonymous Monk on Apr 30, 2018 at 09:46 UTC
Re: Perl CGI.PM: Use of uninitialized value $vals by hippo (Bishop) on Apr 30, 2018 at 08:28 UTC
Something like this will do it (note the "-w" which I suppose you are using too): `#!/usr/bin/perl -w use CGI; CGI->STORE ('foo', undef);` [download] So you can trigger this by passing an undefined parameter value to STORE() but only with "-w". Use warnings instead if you don't want to see it.	[reply] [d/l]
Re^2: Perl CGI.PM: Use of uninitialized value $vals by Anonymous Monk on Apr 30, 2018 at 08:51 UTC
I do not have any CGI code calling CGI->STORE. Perhaps something else that calls CGI->STORE indirectly? What could it be?	[reply]
Re^3: Perl CGI.PM: Use of uninitialized value $vals by haukex (Archbishop) on Apr 30, 2018 at 11:14 UTC
While you could certainly investigate and debug CGI.pm, you really shouldn't use `-w` on the shebang line (`#!/usr/bin/perl -w`) and `use warnings;` instead. See What's wrong with -w and `$^W`.	[reply] [d/l] [select]
Re^4: Perl CGI.PM: Use of uninitialized value $vals by Anonymous Monk on Apr 30, 2018 at 14:37 UTC
Re^5: Perl CGI.PM: Use of uninitialized value $vals by haukex (Archbishop) on Apr 30, 2018 at 21:09 UTC
Re: Perl CGI.PM: Use of uninitialized value $vals by jsteng (Beadle) on Apr 30, 2018 at 06:51 UTC
use warnings; can cause that warning message. but not fatal. usually happens with codes like `use warnings; my %hash; if ($hash{'word'} =~ /world/) { }` [download] $hash{word} is not defined and will cause that warning. Make sure $hash{word} holds a valid value before using it or it will give you a warning.	[reply] [d/l]
Re: Perl CGI.PM: Use of uninitialized value $vals by Anonymous Monk on Apr 30, 2018 at 22:16 UTC
use Carp::Always; # know where the warning originated	[reply]
Re: Perl CGI.PM: Use of uninitialized value $vals by Anonymous Monk on Apr 30, 2018 at 06:24 UTC
Saw this in my web log file today: $vals is not initialised, yes, but what precondition caused the warning to be triggered? Precondition? Some code you wrote somewhere? Some warnings you turned on for code you did not write? Don't turn on global warnings? Dont use old versions of CGI.pm? Be better programmer?	[reply]


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