magical variable $. treated as undef [rt.cpan.org #87084]

[toddr]

Migrated from rt.cpan.org#87084 (status was 'open')

Requestors:

• [email protected]

From [email protected] on 2013-07-20 03:06:22:

Dump() incorrectly treats $. as undef. Here is a quick example : 

use strict;
use warnings;
use YAML::Syck;

my @lines;
open my $fh, "<", $0 or die $!;
while (<$fh>) {
  push @lines, {bad_num => $., good_num => $.+0, line => $_};
}

print Dump(\@lines);

__END__
Output : 
--- 
- 
  bad_num: ~
  good_num: '1'
  line: "use strict;\n"
- 
  bad_num: ~
  good_num: '2'
  line: "use warnings;\n"
<etc.>

From [email protected] on 2016-02-05 04:11:21:

Hi,

On Fri Jul 19 23:06:22 2013, DAMI wrote:
> Dump() incorrectly treats $. as undef. Here is a quick example : 
> 
> use strict;
> use warnings;
> use YAML::Syck;
> 
> my @lines;
> open my $fh, "<", $0 or die $!;
> while (<$fh>) {
>   push @lines, {bad_num => $., good_num => $.+0, line => $_};
> }
> 
> print Dump(\@lines);
> 
> __END__
> Output : 
> --- 
> - 
>   bad_num: ~
>   good_num: '1'
>   line: "use strict;\n"
> - 
>   bad_num: ~
>   good_num: '2'
>   line: "use warnings;\n"
> <etc.>

I can't see an easy way to make that work safely. The parameters to Dump are passed down to the XS function XS_YAML__Syck_DumpYAML and the C code doesn't know about special Perl variables. Example $$ doesn't work either.

By adding 0 for good_num, Perl is evaluating that before it becomes an argument for Dump, and so that on works.

Gordon