Difference between old and new

zatlas1 has asked for the wisdom of the Perl Monks concerning the following question:

I have this script:

perl -e '
        use strict;
        use warnings;
        use Data::Dumper;
        use lib "\/xxx\/common\/bin";
        use DMDCombo2;
        my $x = DMDCombo2->new;
        print Dumper $x;
        my $y = $x->export_envvars;
        print $y;
        '
[download]

my old Solaris and new Linux share the /xxx mount
when run on Solaris with Perl 5.10.0 (I kid you not), I get the expected results
When run on Linux with Perl 5.28, I get
$VAR1 = undef;
Can't call method "export_envvars" on an undefined value at -e line 9.
I cannot share the 'new' code but it ends with:

   bless $self,$class;
   return $self;
}
[download]

What do I do wrong in 5.28 that 5.10 used to tolerate?
Thank you
ZA

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Re: Difference between old and new by Corion (Patriarch) on Nov 13, 2023 at 18:57 UTC
The only thing we can do to help is help you reduce your code so you can show it to us. Somehow the code in `DMDCombo2` returns `undef`. We cannot know why unless you reduce it to something you can show us.	[reply] [d/l] [select]
Re^2: Difference between old and new by zatlas1 (Acolyte) on Nov 13, 2023 at 19:35 UTC
This was a great help. I've found the issue! It is a complex proprietary module, and yes, it does return explicit undef under some circumstances Thank you ZA	[reply]
Re: Difference between old and new by hv (Prior) on Nov 13, 2023 at 18:47 UTC
Sorry, there appears to be insufficient information. The shared `/xxx` mount does not appear to be relevant: you're successfully loading the `DMDCombo2` module, or you would get an error from the `new()` call before you reached the print. It is also not reaching the two lines from the `new` method that you show: if `$self` were undef at that point, you would get an error like "Can't bless non-reference value". So something is going wrong within that `new()` method, causing it to return an undef before it reaches the final two lines. If you cannot show its code, nor a cut-down or sanitised version of it that exhibits the same error, I suggest the following steps: 1) copy the module to somewhere local on the linux box, modify the `use lib` statement appropriately, and satisfy yourself that the shared mountpoint is not the cause of the issue; 2) add diagnostics in the `new()` method in this copy to see which lines it is executing and understand where it is returning. It will almost certainly be hitting an explicit `return` statement in that `new()` method, but diagnostics should easily make it clear where it is reaching; if the answer is not obvious at that point, you will at least have more information to share with us.	[reply] [d/l] [select]
Re: Difference between old and new by InfiniteSilence (Curate) on Nov 14, 2023 at 01:21 UTC
Get out of the habit of evaluating your code in the manner shown. If you must, write a script that does what you want and run it against different Perl versions. I prefer to use Test::More and run that periodically to catch errors that will appear over time as dependencies change. I hear h2xs is deprecated but I will use it for instructional purposes here: `cd /tmp h2xs -AXn junk cd ./junk cd t cat junk.t` [download] Above produces boilerplate test code you can produce literally in seconds. `use strict; use warnings; use Test::More tests => 2; BEGIN { use_ok('DMCombo2');}; ...` [download] Change things for your environment. Six months down the road you will be thanking yourself for investing the time to learn this stuff. Celebrate Intellectual Diversity	[reply] [d/l] [select]