2022 twenty-four merry days of Perl Feed

How to wrap a camel?

Perl::Dist::APPerl - 2022-12-25

How to wrap a camel?

In the elf workshop, elves never knew what to do when they were passed a camel and were instructed to wrap it to put it on Santa's sleigh. Many times the elves skipped wrapping and loaded camels right onto the sleigh. This practice garnered the North Pole many letters from children around the world being unable to install and use their new camel! "How do I install Perl?", "cpanm: command not found", "Permission denied", "collect2.exe: error: ld returned 1 exit status", "Can't locate" they cried out for help. Some gift recipients even refused to install their camel despite their needs and desires, as they didn't want to deal with the difficulties of installing Perl. Claus tasked master elf, Artie, to design a fool-proof way of wrapping a camel for enjoyment by children across the world.

Artie got right to work as they knew from experience that wrapping a camel was not a trivial task. First, Artie attempted to wrap a camel with PAR::Packer, but discovered that the wrapped camel was unusable when the user's glibc version or operating system differed from the one Artie used to wrap. Artie knew Santa had high standards and would want a more robust solution, so they continued to do research. Artie stumbled upon the Cosmopolitan Libc and Actually Portable Executables. What if you built a single binary version of Perl that runs on six operating systems and melded your camel to the binary? Then, everyone can use camels! Artie got to work creating Actually Portable Perl (APPerl) with the Perl::Dist::APPerl package for building APPerl and wrapping camels with it.

Close to Christmas, Artie finally had Perl::Dist::APPerl ready and notified Santa. Santa requested an immediate demonstration to determine if it is a viable way of wrapping camels starting this Christmas season.

Wrapping Pure Perl camels

Artie created some directories to contain the camel project.

    mkdir -p wrap_camel/src wrap_camel/script
    cd wrap_camel

Artie created an example script and saved it to script/cameltype:


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sub cancel_christmas { die "$!"; }
my $numhumps;
while(1) {
    print "How many humps?\n";
    $numhumps = <STDIN> or cancel_christmas();
    chomp $numhumps;
    last if($numhumps =~ /^\d+$/);
    print "Your nose ain't too bright, $numhumps is not a number\n";
}
my %results = (1 => "Dromedary\n", 2 => "Bactrian\n");
print($results{$numhumps} // "Maybe a reindeer? Probably not a camel!\n");

 

Artie noted to Santa that Pure Perl scripts can be wrapped with an existing version of APPerl, off the shelf builds of APPerl can be found on the APPerl webpage.

Artie picked perl-small.com off the shelf and created an APPerl project:

    wget -O src/perl.com 'https://github.com/G4Vi/Perl-Dist-APPerl/releases/latest/download/perl-small.com'
    chmod +x src/perl.com
    apperlm init --name default_config

Artie edited default_config in the newly created apperl-project.json to copy in the cameltype script and set the destination executable name to cameltype.com, the name is important as argv[0] is used to determine which script embedded in APPerl to run.

    "dest" : "cameltype.com",
    "zip_extra_files" : { "bin" : ["script/cameltype"] },

Artie wrapped the camel and demonstrated the cameltype binary:

    apperlm build
    ./cameltype.com

Santa said, "Ho, ho, ho. Very impressive, Artie! What about the camels with XS modules?"

Wrapping camels with XS modules

Artie said, "Camels with XS modules can also be wrapped into APPerl. However, every XS-wrapping elf needs a Linux build environment." Santa, a big fan of developing on several platforms, asked, "Why is that required?" Artie replied, "While APPerl binaries are also ZIP files, APPerl binaries are statically linked, so there is no way to add binary modules after compilation. To wrap with XS modules, the Cosmopolitan Libc and Perl must be built from scratch." Santa was reasonably worried about this and asked Artie to show him once more.

Artie ran some commands to create a new APPerl project and install build dependencies:

    mkdir -p ../wrap_xs_camel/script
    cd ../wrap_xs_camel
    apperlm install-build-deps
    apperlm init --name default_config --base v5.36.0-small-v0.1.0

Artie created MerryChristmas.xs:


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#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include <stdio.h>

MODULE = MerryChristmas PACKAGE = MerryChristmas

void
merry_christmas()
    CODE:
        printf("Merry Christmas from XS!\n");

 

Artie created MerryChristmas.pm:


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package MerryChristmas;
our $VERSION = '0.0';
require XSLoader;
XSLoader::load("MerryChristmas", $VERSION);
1;

 

Artie created a script/merrychristmas to demo the module:


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use MerryChristmas;
MerryChristmas::merry_christmas();

 

Artie edited default_config in apperl-project.json to add the MerryChristmas module to the Perl repo, copy in the script, and set the destination executable name.

    "dest" : "merrychristmas.com",
    "perl_repo_files" : { "ext/MerryChristmas" : ["MerryChristmas.pm", "MerryChristmas.xs"]},
    "+MANIFEST" : ["__perlarchlib__/MerryChristmas.pm", "bin/merrychristmas"],
    "+perl_onlyextensions" : ["MerryChristmas"],
    "zip_extra_files" : { "bin" : ["script/merrychristmas"] }

Artie checked out the config, configured, built, and tested out the Merry Christmas message contraption:

    apperlm checkout default_config
    apperlm configure
    apperlm build
    ./merrychristmas.com

Santa said, "Great work, now we can wrap camels of all shapes and sizes to spread cheer to the world! I'd like to put this into practice immediately". Artie replied, "Thank you Santa, I'll get to work teaching all the other elves how to wrap a camel."

Gravatar Image This article contributed by: Gavin Hayes <gahayes@cpan.org>